MyFishFinder Forum
MFF US Northeast => Maine => Topic started by: fishlessman on Jul 24, 2018, 07:52 AM
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1991 115 merc, i believe its a 2+2. i get it up on plane at 4000 rpm, then it cuts out to about 2400 rpm, then slams back to 4000 again every minute or two. what operates the 2+2 function on the carbs. some times i have full power for a half hour then this starts, sometimes it starts this way first thing. tough to bring it to a shop where you cant show them whats happening
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Start with your anti- siphon valve coming out of your fuel tank then check all of the fuel lines all the way to the carbs. The ethonal gas rots your fuel lines from the inside and sometimes a piece will act like a valve or if a line is making a bend when your asking for more fuel the suction will collapse the line.
I was out in your area in a friends boat a few weeks ago and he started having the same issue, changed out his fuel lines and the problem went away.
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Start with your anti- siphon valve coming out of your fuel tank then check all of the fuel lines all the way to the carbs. The ethonal gas rots your fuel lines from the inside and sometimes a piece will act like a valve or if a line is making a bend when your asking for more fuel the suction will collapse the line.
I was out in your area in a friends boat a few weeks ago and he started having the same issue, changed out his fuel lines and the problem went away.
I am with stguy.
I had a very similar issue and come to find out my fuel line rotted and it was clogging my fuel from getting to my engine. They were tiny little clear plastic particles.
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ive had that problem two years ago, it was between the tank and ball and would collapse the ball. i did not change the line between the ball and carbs though, easy to change that section. this seems more like the power transition between running on 2 cylinders to when it switches to 4 as the rpms seem to drop and raise consistantly. if changing the line doesnt work, i have a second tank to try and run it with.
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I am with stguy.
I had a very similar issue and come to find out my fuel line rotted and it was clogging my fuel from getting to my engine. They were tiny little clear plastic particles.
theres a very thin clear liner in the newer hoses that can de-laminate inside the hose, really hate ethynol. going to try the other tank i run the kicker on with the bigger motor, that should give me a better idea with regard to the lines
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If it's not a fuel issue, try moving all the wires around and see if you can make it happen, could be a loose connection??
It also sounds like it could be a coil breaking down??
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If it's not fuel or plug wire it may be carbon fouled?? As in the passages to the other cylinders on the down stroke it pulls fuel in on up stroke it fires . Like a two stroke.. try running a good fuel treat ment like sea foam if this is the case.. try last if not fuel hose or filter? or wires like stguy was saying..
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If you get as far as the sea foam and it works maybe replacing the spark plugs and wires on all cylinders.. this the cause of carbon fouling usally.. incomplete combustion not stoich as in stokyo metric efficiency like a 14:1 ratio of combustion.. even ignition timing being retarded can cause fouling... or over oiling ?? As in to rich of fuel.. that's if the sea foam works?? Always look at the spark plugs and look at charts and compare what's going...if wondering....
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Start with your anti- siphon valve coming out of your fuel tank then check all of the fuel lines all the way to the carbs. The ethonal gas rots your fuel lines from the inside and sometimes a piece will act like a valve or if a line is making a bend when your asking for more fuel the suction will collapse the line.
I was out in your area in a friends boat a few weeks ago and he started having the same issue, changed out his fuel lines and the problem went away.
Did you own an ST1100
Or ST1300
Asking because of your name here.
Thanks
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If you get as far as the sea foam and it works maybe replacing the spark plugs and wires on all cylinders.. this the cause of carbon fouling usally.. incomplete combustion not stoich as in stokyo metric efficiency like a 14:1 ratio of combustion.. even ignition timing being retarded can cause fouling... or over oiling ?? As in to rich of fuel.. that's if the sea foam works?? Always look at the spark plugs and look at charts and compare what's going...if wondering....
Stoichiometry is 10:1 for naturally aspirated combustion.
14:1 is excess air and you’ll burn up pistons with the flame temps being too hot.
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Did you own an ST1100
Or ST1300
Asking because of your name here.
Nope...had cb, kz, fj, gl, yz, rm, it, and a few others but never an st, they are cool looking bikes though.
Thanks
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Nope...had cb, kz, fj, gl, yz, rm, it, and a few others but never an st, they are cool looking bikes though.
mine on the right in 1996
My dad on the yellow BMW.
He died on it 3 yrs later.
My sone Jeff on the left.
He's 33 now.
My son chris on the right.
He's 31 now.
(https://s8.postimg.cc/lbvordof5/macbikepic.jpg) (https://postimg.cc/image/lbvordof5/)
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Stoichiometry is 10:1 for naturally aspirated combustion.
14:1 is excess air and you’ll burn up pistons with the flame temps being too hot.
Rethink that it's really 14.7:1
As seen here..
https://www.google.com/search?ie=UTF-8&client=ms-android-att-us&source=android-browser&q=air+fuel+ratio
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Stoichiometry is 10:1 for naturally aspirated combustion.
14:1 is excess air and you’ll burn up pistons with the flame temps being too hot.
Compression ratio is 10:1 on gas motor but can be as high as 14:1 for diesel motors
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Compression ratio is 10:1 on gas motor but can be as high as 14:1 for diesel motors
1st - you were speaking about gas to fuel ratio, or Stoichiometry. Stoichiometry for a naturally aspirated combustion engine is 10:1. Not 14:1
2nd - it's been a long time since I've seen a diesel outboard
3rd, and lastly, I said that a 14:1 air/fuel ratio would be running excess air, or lean. A lean burn produces a hotter flame and CAN burn up pistons. Further, that is, unless things have been designed to handle a lean fuel ratio you don't want mess with what the motor was designed for unless you know what you are doing. Things like running higher octane fuel to slow down the burn rate and/or using higher compression ratios, and advancing/retarding the ignition timing to avoid detonation are all options when playing with air/fuel ratios. But you had better know what you are doing.
But, again, you were attempting to speak about Stoichiometry in your original post Boon and I simply corrected and/or clarified what you posted.
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Rethink that it's really 14.7:1
As seen here..
https://www.google.com/search?ie=UTF-8&client=ms-android-att-us&source=android-browser&q=air+fuel+ratio
What you posted here (the link) is correct.
Except, as I posted below, we are not speaking about diesel fuel (or alcohol).
Stoichiometry for natural gas and gasoline is closer to 10:1, not 14:1.
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If it's not a fuel issue, try moving all the wires around and see if you can make it happen, could be a loose connection??
It also sounds like it could be a coil breaking down??
While I agree it sounds like it could very well be an electrical gremlin, it would be rare to have a coil with an intermittent problem like that. They tend to either work or not. Anything is possible though.
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This one worked great until I hit 4100 rpm, and then not so much, sometimes
You are correct, usually they either work or they don't.
(https://s8.postimg.cc/tbnxm84zl/20180716_100831.jpg) (https://postimg.cc/image/tbnxm84zl/)
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the 2+2 engine is a simple but at the same time complex engine... the actual "kick in" of these is caused by fuel being metered by the second progression hole in the lower 2 carburetors.. controlled by the carburetor linkage.. this is why set up is so crucial on these motors... an accelerator pump with the aid of 2 check valves helps that resemble needle and seats more than check valves, Controls acceleration. during idle.. only the top 2 carburetors have air/fuel mixture screws... the lower 2 receive a token amount of fuel but lacking air cannot fire , this lubricates the lower cylinders and the fuel is scavenged and burned by the upper 2 cylinders via a complex network of check valves and bleed hoses ... once the throttle plates are opened the accelerator pump takes over for the temporary lean condition and the carburators then meter fuel via the main jet like a normal carb....
Now for your problem...most likely you have a bad coil... it's very common on those engines... a stator or trigger is also a strong possibility but I'd place money on the coil.
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the 2+2 engine is a simple but at the same time complex engine... the actual "kick in" of these is caused by fuel being metered by the second progression hole in the lower 2 carburetors.. controlled by the carburetor linkage.. this is why set up is so crucial on these motors... an accelerator pump with the aid of 2 check valves helps that resemble needle and seats more than check valves, Controls acceleration. during idle.. only the top 2 carburetors have air/fuel mixture screws... the lower 2 receive a token amount of fuel but lacking air cannot fire , this lubricates the lower cylinders and the fuel is scavenged and burned by the upper 2 cylinders via a complex network of check valves and bleed hoses ... once the throttle plates are opened the accelerator pump takes over for the temporary lean condition and the carburators then meter fuel via the main jet like a normal carb....
Now for your problem...most likely you have a bad coil... it's very common on those engines... a stator or trigger is also a strong possibility but I'd place money on the coil.
Do you know anything about props?
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Do you know anything about props?
Don’t hit a rock with them.
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Don’t hit a rock with them.
Only done that once, talking on the phone while leaving the basin and kept the red markers on my right, whoops!
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Only done that once, talking on the phone while leaving the basin and kept the red markers on my right, whoops!
Red right RETURN. lol
No more talking on the phone while driving a vehicle or boat here in RI.
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Do you know anything about props?
.. yes..more than the average boat owner..and then some...
I may have a set of coils and a switch box for that 91 merc... I had a 95-115 2+2 that lost a fly wheel and ate the stator and trigger...it was cheaper to buy a used engine than buy a flywheel and ignition system because the flywheel was obsolete and it would require the entire ignition system to be changed.. I stripped the carbs and electrical system off of the motor thinking it was going to fit my 2004 115- 2+2( spare parts not knowing they would not work)... but they changed the electrical system a bit by eliminating the switch box and went to straight CD cols power packs...I'll look and see if I still have the coils and switch box...I also may have a 17 and 19P aluminum prop...I've given some stuff away ( helped a few others in your predicament)..not sure whats left from that motor.. what I do have can be had for the cost of shipping or you can come and get it for free.
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.. yes..more than the average boat owner..and then some...
I may have a set of coils and a switch box for that 91 merc... I had a 95-115 2+2 that lost a fly wheel and ate the stator and trigger...it was cheaper to buy a used engine than buy a flywheel and ignition system because the flywheel was obsolete and it would require the entire ignition system to be changed.. I stripped the carbs and electrical system off of the motor thinking it was going to fit my 2004 115- 2+2( spare parts not knowing they would not work)... but they changed the electrical system a bit by eliminating the switch box and went to straight CD cols power packs...I'll look and see if I still have the coils and switch box...I also may have a 17 and 19P aluminum prop...I've given some stuff away ( helped a few others in your predicament)..not sure whats left from that motor.. what I do have can be had for the cost of shipping or you can come and get it for free.
I'll shoot you a pm about my prop question if you don't mind??
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Only done that once, talking on the phone while leaving the basin and kept the red markers on my right, whoops!
Did it once myself. First year I had my boat down here about 10 years ago. First time going out on Sebago through the gut after ice out from Jordan’s. One of the don’t go between here and shore before the ferry cove was gone. Maybe ice took it. I found the rock at about 25 mph.
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I'll shoot you a pm about my prop question if you don't mind??
works for me..
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the 2+2 engine is a simple but at the same time complex engine... the actual "kick in" of these is caused by fuel being metered by the second progression hole in the lower 2 carburetors.. controlled by the carburetor linkage.. this is why set up is so crucial on these motors... an accelerator pump with the aid of 2 check valves helps that resemble needle and seats more than check valves, Controls acceleration. during idle.. only the top 2 carburetors have air/fuel mixture screws... the lower 2 receive a token amount of fuel but lacking air cannot fire , this lubricates the lower cylinders and the fuel is scavenged and burned by the upper 2 cylinders via a complex network of check valves and bleed hoses ... once the throttle plates are opened the accelerator pump takes over for the temporary lean condition and the carburators then meter fuel via the main jet like a normal carb....
Now for your problem...most likely you have a bad coil... it's very common on those engines... a stator or trigger is also a strong possibility but I'd place money on the coil.
i replaced the stator a few years ago. its acting differently then before when it went. now with the coils, if i flip the 2 uppers with the lower im thinking it would act differently than it is now if one of the lower coils is bad with this motor? going to run down the gas lines first for problems but that seems to be the next logical step. probably a job for the late fall as i dont see taking it out of the water til then. if its a coil it has to be one of the lower two the way its running
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No more talking on the phone while driving a vehicle or boat here in RI.
Got spoken to last year here in NH by Marine Patrol while on Winnisquam travelling at headway speed. Very lucky I avoided a ticket.
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1st - you were speaking about gas to fuel ratio, or Stoichiometry. Stoichiometry for a naturally aspirated combustion engine is 10:1. Not 14:1
2nd - it's been a long time since I've seen a diesel outboard
3rd, and lastly, I said that a 14:1 air/fuel ratio would be running excess air, or lean. A lean burn produces a hotter flame and CAN burn up pistons. Further, that is, unless things have been designed to handle a lean fuel ratio you don't want mess with what the motor was designed for unless you know what you are doing. Things like running higher octane fuel to slow down the burn rate and/or using higher compression ratios, and advancing/retarding the ignition timing to avoid detonation are all options when playing with air/fuel ratios. But you had better know what you are doing.
But, again, you were attempting to speak about Stoichiometry in your original post Boon and I simply corrected and/or clarified what you posted.
Seriously mac you better do more research..
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i replaced the stator a few years ago. its acting differently then before when it went. now with the coils, if i flip the 2 uppers with the lower im thinking it would act differently than it is now if one of the lower coils is bad with this motor? going to run down the gas lines first for problems but that seems to be the next logical step. probably a job for the late fall as i dont see taking it out of the water til then. if its a coil it has to be one of the lower two the way its running
Good luck.. seems like you have it under control.
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.. yes..more than the average boat owner..and then some...
I may have a set of coils and a switch box for that 91 merc... I had a 95-115 2+2 that lost a fly wheel and ate the stator and trigger...it was cheaper to buy a used engine than buy a flywheel and ignition system because the flywheel was obsolete and it would require the entire ignition system to be changed.. I stripped the carbs and electrical system off of the motor thinking it was going to fit my 2004 115- 2+2( spare parts not knowing they would not work)... but they changed the electrical system a bit by eliminating the switch box and went to straight CD cols power packs...I'll look and see if I still have the coils and switch box...I also may have a 17 and 19P aluminum prop...I've given some stuff away ( helped a few others in your predicament)..not sure whats left from that motor.. what I do have can be had for the cost of shipping or you can come and get it for free.
I think I have the lower unit off that motor, joe. still working great
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Come on guys help out fishlessman. We now know that the unilateral phase detractors cannot synchronize with cardinal grammeters without magnetic flux disturbance.
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Come on guys help out fishlessman. We now know that the unilateral phase detractors cannot synchronize with cardinal grammeters without magnetic flux disturbance.
i have all that figured out, now to get a lobster boat upta 88 mph to get it all to work. im probably going to keep it under 2.5 for the weekend though ;D
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i have all that figured out,
Great to hear.
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If I had known you where traveling in time I would have suggested a leak in the plasma field that suspends your flux capacitor, if your flux capacitor grounds out it will cause random and sometimes drastic drops in rpm, a real bummer if you haven't reached your destination, a part of you could end up in Jordan bay.
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I probably missed it, but did anyone specify the rate of encabulation at operating temperatures? If the rate is too low, you may have to install an aftermarket panametric fan.
Sorry to hijack fishlessman...all in good fun.
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i have all that figured out, now to get a lobster boat upta 88 mph to get it all to work. im probably going to keep it under 2.5 for the weekend though ;D
If I had known you where traveling in time I would have suggested a leak in the plasma field that suspends your flux capacitor, if your flux capacitor grounds out it will cause random and sometimes drastic drops in rpm, a real bummer if you haven't reached your destination, a part of you could end up in Jordan bay.
This guy should be able to help you out. I sent him a telegram.
(https://i.ytimg.com/vi/acZ_apyP81s/hqdefault.jpg)
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I was waiting for someone to post that picture
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Seriously mac you better do more research..
All he needs is the definition of pre ignition/detonation. Higher octane is less prone to preignition (combustion in the cylinder before the spark is thrown).
A lean burn whatever that is doesnt produce a hotter flame....a lean situation may or may not cause pre ignition. There are about a zillion variables that go into what cause knock. So mac is aware a lean knock is a result of combustion prior to ignition. Its an explosion for lack of a better description...and the fuel does not burn in a uniformed fashion and does so before the piston reaches TDC and before a spark is thrown. (In severe cases)
When to your second hobby is putting 20+ psi down a cars throat you learn these things very quickly!
The solution to this boating issue is Joe. Joe knows!
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I think I have the lower unit off that motor, joe. still working great
you sure do... there's a few people still running today thanks to that motor.. I still have the short block...one of these days it's going to bail some one out of trouble.
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you sure do... there's a few people still running today thanks to that motor.. I still have the short block...one of these days it's going to bail some one out of trouble.
You are the man.
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You are the man.
Id 2nd this if he had 1990 evinrude looper parts! :)
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All he needs is the definition of pre ignition/detonation...………………….
I'm a combustion engineer.
40+ yrs.
ME too.
Also built and raced "vehicles" over the years.
Put myself thru college wrenching on engines and transmissions in my dad's auto shop.
I tried to "dumb down" or simplify my response to his original post, as he was incorrect in what he was "trying" to say.
But that's ok.
I'll be busy for a while now.
Out googling sites for "more research".
:rotflol: :rotflol: :rotflol:
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It's all fun and games until someone melts a piston Mac.
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It's all fun and games until someone melts a piston Mac.
Yup!
Lol
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I'm a combustion engineer.
40+ yrs.
ME too.
Also built and raced "vehicles" over the years.
Put myself thru college wrenching on engines and transmissions in my dad's auto shop.
I tried to "dumb down" or simplify my response to his original post, as he was incorrect in what he was "trying" to say.
But that's ok.
I'll be busy for a while now.
Out googling sites for "more research".
:rotflol: :rotflol: :rotflol:
I would go get your money back on that degree cause obviously they did not teach you about any thing!! like humility.. by the way mac every thing you pointed out makes me correct on what I said.. cause its same thing as your saying thanks for proving me correct... except for 10:1 ratio Is incorrect for gasoline and correct for alcohol.. now if you read link below gasoline is a 14.7:1 for stoich any thing above stoich is lean any thing below is rich like I was saying in posts 6 and 7 of this thread...and thanks again for proving me more them correct by the way mac that link is correct just got to scroll down to read the garret turbos site that points out gasoline stoich is 14.7:1 and thanks again mac for the good laugh..
Scroll down on this hyper link to see the garret Web site pointing out that stoich is 14.7:1 on gasoline engines..
https://www.google.com/search?ie=UTF-8&client=ms-android-att-us&source=android-browser&q=air+fuel+ratio (https://www.google.com/search?ie=UTF-8&client=ms-android-att-us&source=android-browser&q=air+fuel+ratio)
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I prefer a nice precision turbo myself... 8)
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I prefer a nice precision turbo myself... 8)
Twin?
;)
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Twin?
;)
I guess the topic here has run its course soo...
Those are large single ball bearing turbos they spin up pretty fast despite having large AR's.
More on topic...merc makes a supercharged outboard. Crazy to me because boost is a tricky, fickle thing, performance constantly changing with the weather....I wonder how reliable they are...
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how quick does a supercharged merc get to 2.2 mph 8)
i just retired my 89 dakota that i purchased in 1989, 125 hp slug, 0 to 60 in 25 seconds. replaced it with a 2010 510 hp rover, this has been a learning experience, if i stop posting here you will know i rolled it
changed to a different tank on the boat, its the gas line, hoping when the floor was put in last they made the line access loose and didnt just foam it in solid. i can change out the water separator and line to the motor easily, theres no good access under the floor, thats a job for the fall
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changed to a different tank on the boat, its the gas line,
glad you found the problem
:clapping:
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changed to a different tank on the boat, its the gas line, hoping when the floor was put in last they made the line access loose and didnt just foam it in solid. i can change out the water separator and line to the motor easily, theres no good access under the floor, thats a job for the fall
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We had you with response 1 and 2. LOL
Some great info in this thread that's for sure!
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Thankfully there was some close project coordination and preliminary operational tests proved conclusive. ;D
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changed to a different tank on the boat, its the gas line, hoping when the floor was put in last they made the line access loose and didnt just foam it in solid. i can change out the water separator and line to the motor easily, theres no good access under the floor, thats a job for the fall
We had you with response 1 and 2. LOL
Some great info in this thread that's for sure!
getting close, it could be the tank vent line breaking down ;D
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Thankfully there was some close project coordination and preliminary operational tests proved conclusive. ;D
also known as the ballmer peak
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Assuming that your boat has a built in tank, it could be your anti-siphon valve, unlike a plasma containment field for your flux capacitor, it really is a thing, and they can cause the kind of problem your having.
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Thankfully there was some close project coordination and preliminary operational tests proved conclusive. ;D
SAT words gallore!
Fishlessman...having worked on a few of them...I hope you have better luck fishing!
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You guys play nice or you’re gonna go sit in the car
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and for whatever reason it works great now, no need to fix it now ;D
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If you have more problems check the oil tank. I believe you have the same motor as we did with the oil fill tank on top we had a bunch of water in our oil tank sounds like the same problems we had