1987 johnson 88 hp spl bogs down after warmup

[crabbydad]

i put this motor on my boat last year. ran great, great compression. this year first time out, started out fine, got right up on plane. then started to bog down and would only plow through water. i thought maybe it was a bad coil. crabbed for a couple hours and when it was time to head in it got up on plane. took it out a week later and it ran great. took it out today, got right up on plane, after 5 minutes or so, it bogged down and only plowed through the water. did this for several hours as i was back and forth between crabbing runs. then after a long run it did start to pick up. once i throttled down it would still only plowed through the water. i had this same type of problem once on the previous motor on this boat and it was the power pack. when i checked , all cyclinders were firing(under no load) if i raise the warmup lever, it revs up fine. could the timing not be advancing? i cannot manually advance by pulling the arm. any thoughs on what to check?
thanks

 

[James R]

Re: 1987 johnson 88 hp spl bogs down after warmup

When were the carbs last serviced? Do you have crap in the tank. Will the motor pick up if you squeeze the bulb.

 

[crabbydad]

Re: 1987 johnson 88 hp spl bogs down after warmup

the motor will not pick up if i squeeze the bulb. i wonder if maybe one of the coils is going bad. it ran great last week and yesterday for about 5 minutes.

 

[James R]

Re: 1987 johnson 88 hp spl bogs down after warmup

I ask you again. When were the carburetors last serviced. If you don't know then it is time they were. Trying to run with bad carbs will kill the motor.

 

[toddschubert]

Re: 1987 johnson 88 hp spl bogs down after warmup

I had same problem...check the roller for timing advance rod. If the rubber is worn there may be too much slack in it.
Also try running some SeaFoam through it for a while. That helped me tremendously. one bottle to 12 gallons

 

[crabbydad]

Re: 1987 johnson 88 hp spl bogs down after warmup

not sure last time carbs were serviced. i bought the motor used the end of last summer. maybe its time to pull em and clean em. i was wondering if maybe it someting to do with th timing. on my old motor i could amnually advance the timing. on this motor, the roller rides in a circular groove. everything is tight, i can't move anything.

 

[James R]

Re: 1987 johnson 88 hp spl bogs down after warmup

Not likely that the timing has changed unless it has been messed with. You can kill a good motor just trying to make it run with dirty carbs. Remember the lubrication relies on clean carbs. Carbs are a good place to start. Of course you could have dropped a cylinder.

 

[crabbydad]

Re: 1987 johnson 88 hp spl bogs down after warmup

i checked the compression, all cylinders are between 120-125 psi. its strange how it bogged down the firrst time out, then the next time it ran great the whole time out, then the third time bogged down again. i did clean the filter at the fuel pump and replaced the inline fuel filter. both were dirty. i can't tell if this made any difference because it runs fine on muffs. also the control is really tight. i gonna make sure it is moving to the wot position.
thanks for the help

 

[toddschubert]

Re: 1987 johnson 88 hp spl bogs down after warmup

Runs on muffs cuz no load

 

[crabbydad]

Re: 1987 johnson 88 hp spl bogs down after warmup

pulled the carbs and cleaned them. one of the intermediate orifices was completely clogged. would that be enough to make it run this way? i guess i'll find out when i trake it out

 

[Vitamin Sea]

Re: 1987 johnson 88 hp spl bogs down after warmup

pulled the carbs and cleaned them. one of the intermediate orifices was completely clogged. would that be enough to make it run this way? i guess i'll find out when i trake it out

did the carb job help i have the same problem

 

[fireman57]

Re: 1987 johnson 88 hp spl bogs down after warmup

Undo the hose from the fuel pump, put a clear line on it and crank the engine. If you have bubbles in there then you have an air leak. Make sure you pull the plugs so the engine can't start or at least have it on muffs.

 

[crabbydad]

Re: 1987 johnson 88 hp spl bogs down after warmup

i finally got a chance to take the boat out. it ran great. besides cleaning the carbs, i also changed the fuel filter and cleaned the screen in the fuel pump, and swapped spark plugs with another motor i have.