outboard help

Chris Finch

Chris Finch

Well-known member
i took my boat for a ride today and everything was going well. i was cruising around the lake at full trotle for a while 20-25 minutes. then i noticed that the motor started to run rough and bogged down. it is fine up to 3/4 throttle, then it bogs. it starts right up and runs great at low speed, and is pissing water. the whole tank is fresh gas, and has a new fuel line and bulb.

it is a 1998 merc 2 stroke 15 hp tiller short shaft.

i would think carb if it was always like that but after that long it full throttle i am thinking an electrical problem. maybe coils? any help would be appreciated, thanks Chris.
 
Its a Merc.....enough said HaHaHaHa
I had a run in with a Merc the other day on a test run.....1st and last LOL
 
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I'd try the tank vent first, then the filter and then the hose clamps. Its starving for gas and either can't get gas or is sucking air. Start simple and cheap and then get into the expensive and complex repairs.
 
I'd try the tank vent first, then the filter and then the hose clamps. Its starving for gas and either can't get gas or is sucking air. Start simple and cheap and then get into the expensive and complex repairs.
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Agreed! Do no harm:)))
 
I would try to determine whether the problem is with the fuel tank or the engine first. A cracked fuel pickup tube will suck air and the fuel pump will not get enough fuel into the carb. If the engine runs OK when the fuel tank is full but then runs rough or stalls as the fuel level gets lower I would suspect the tank.

Might save you a lot of time before taking off the carb for cleaning. Much easier just topping off the tank again to see if it helps.
 
Chris, All good advice so far. To check tank vent just take the cap off and see what happens. If you can borrow an inductive pickup timing light hook it up and go for a ride, if you loose spark you can see the timing light stop flashing. I am also sorry you have a Merc;-(. Nothing like a little brand loyalty sparing. At least it is a 2 stroke (more smilely faces).Try that and keep us posted- Plenty of free advice here!!! You may just try another tank and hose, just sayin. Good Luck
 
Thanks for the ideas guys ill go through the tank tommOrow and take it for a ride on wednesday and see what happens
 
I have to respectfuly dissagree and this is why. the idle/ slow jets are soo much smaller than a high speed/main that they are the ones that clog first. That would either give you a poor idle or even a no start. The time frame leads me to suspect ignition failure BUT it is a Merc after all. (Several more smiley faces). I been wrong before but this is my $.02.
 
Have you every replaced your fuel pump? Cracked diaphragm will do it too. Easy enough to pull apart and take a look.
 
I just got the motor. I checked the fuel line/tank and its good. I took it out this morning it ran wide open when its was cold then after it warmed up it felt like it wasnt hitting power band. Im going to pull the carb assembly off tonight after work
 
Like someone else said,clean the carb real good all the jets and needles,
what happened is that high speed run dislodged some crap and now its blocking the flow.
 
I was was having the same intermittent problem with a 15hp Johnson last season. I would clean the carb and would be fine for a few trips. (I'm running over an hour round trip.) Then it would act up again. Put a small inline fuel filter inside the hood, just after the fuel fitting. Never had a problem the rest of the season. Just a thought!
 
Plugged/clogged high speed jet..maybe? Clean the carb and i bet you will be all good.
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Jet unscrew from the botton of carb bowl. If the gas tank and lines and fuel are ok then i would bet its the jet. Unscrew it and blow it out with air compressor.
 
Rethinking my earlier post, the idle jets are probably (I'm pretty sure) located in the top of the carb and drain every time the engine is shut off. A design stroke of brilliance. Do drop the float bowl and see what kind of mystery stuff is there. Good luck.
 
I finaly got the carb rebuild kit and put it in. It got al new gaskets, fuel pump diaphram, new primer assembley and a good cleaning. It was actualyjunk free but i sprayed it out with carb cleaner anyway.

But on the second lap it started acting up. What do you guys think i should do
Other than dump the pos in the lake
 
I think you should start at the tank and work your way back to the motor. Tank and hose with primer bulb will run you $50-60. Someone earlier suggested you check the gas filter. Most of the little ones you can take apart and clean and it is pretty simple(it doesn't take much dirt to clog it). And if that doesn't work, take it to somebody that works on them because you will end up spending more fixing things that aren't broken, and still not be confident in your motor.
 
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