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Help Mercury 115HP Outboard Problem Running

gkennedy

New member
"Any ideas?
1. I just boug


"Any ideas?
1. I just bought a 1988 pontoon bought with a Merc 115hp outboard motor.

2. When we tested it with ears it ran fine both in neutral and in gear.

3. Draged it 500 miles home. Tested it again with ears and it ran fine.

4. When I put it in the water, it started and ran fine in neutral. When I put it in gear, it was sluggish and I could only get 1500 to 1800 RPM. Thats all the throttle it would take before it died. In neutral it would idle ok and run up to 4k to 5k with decent response.

5. After about 5 to 10 minutes time it deteriorated to the point where it would not take any throttle in gear and would die. Yet in neutral it still seemed to idle and run fine 4k to 5k+ with decent response. It idles at about 1000 RPM for as long as I let it. As soon as I put it in gear it drags down to about 600 RPM and wont take any throttle and dies.

6. I also noticed that the few times I checked the fuel bulb after it died it was soft with no fuel.

7. The altitude change from where I bought it to home is only about 1500 feet. The fuel was fresh.

I'd really appreciate any advice someone has to offer."
 
Stop winding it up in nuetral-

Stop winding it up in nuetral---It is not good for the engine.Start your trouble shooting with a compression test. Followed by a check that you have spark at each cylinder that will jump a gap of 7/16".If those check out OK then the carburetors may need cleaning---motors that sit with fuel in the carburetors for a long time tend to have the small jets in the carburetors plugged up.Best to sort this out before you damage the motor---No fuel going into a cylinder also means no oil.
 
Thank you. I'll do that an

Thank you. I'll do that and I appreciate the advice. I wont rev it in neutral. Actually I only did it maybe 4 times total. Just enough to see the difference between load and no load. I'm not an engine guy but it does act like some sort of fuel issue. Too much or to little or suckng air. The fuel lines look a little warn and I saw a little fuel leaking around the bulb. Thanks again
 
"It's a 6 cylinder. BTW, t

"It's a 6 cylinder. BTW, the previous owner told me he had a problem with it running rough so he had the carbs rebuilt. That didnt seem to help much so the local shop R and R'd the trigger and stater. After that he said it has been "running like a champ". I have a copy of the bill so I'm sure the work was done. It has 3 fuel tanks run through a valve and an external fuel filter. Thanks for the help."
 
Everybody rebuilds carburetors

Everybody rebuilds carburetors as a first attempt to correct problems---do not know why. Do the compression test first.It is essentially a " no money " check and tells a lot about actual motor condition.
 
"Make sure the breathers are o

"Make sure the breathers are open on the fuel tanks.

Replace any fuel filters that may be fitted.

Check for any kinked or twisted fuel lines.

It seems to me that it isn`t sucking fuel freely from the tanks.

If that doesn`t rectify your problem, rebuilding your fuel pump would be next.

It will rev freely in neutral as there is no load on the motor but doing this you run the very real risk of blowing up your engine."
 
also check fuel fiting i had o

also check fuel fiting i had one the leak air but not gas it would run for a while then die
 
Thanks guys for all the help.

Thanks guys for all the help. Took it to the ER and here's what the Boat Doc found. LOL

1. #1 cyl. not fireing. R&R the power pack.
2. Internal fuel lines deteriorated gumming up carbs. The stuff gets like tar. R&R those also.
3. Cleaned and kitted the carbs including needles and seats.
4. R&R fuel filter.

We put it the water yesterday and after adjusting the idle it ran great. Might still need a little mixture adjust as it's just a touch rough at up to 2500 rpm in gear but not enough to cause any problems or concerns. Above that it smooths out and max's at about 5600 rpm. I'll probably run it a while before any more adjustments just to let everything stabilize first. Thanks again. it was all the bits and pieces in the forum that led us in the right direction.
 
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