Time to rebuild the carbs?

[clemsonteg]

I have been chasing a problem on my 1978 85hp Johnson for several weeks now. The issue is the motor would not rev more than 3600 rpm running down the lake. At first I thought it was a coil because I had 1 that was arc out of the boot so I replaced it. Boat did well and then started acting up again.

I then found a kinked fuel hose because someone used bulk hose instead of the factory heat formed hoses. So I ordered factory hoses and rebuilt the fuel pump since I was in that area and the kit was 10 bucks.

My last run I could get to 4600 rpm. Which put me in range and I figured I just need a reprop since th motor isn't original to the boat. Tha brings me to this weekend. I ended up at the same wot of 3600 rpms. Then on the way back to the dock it was like I got rear ended the rpms shot up to 4600 and we were cruising at 21 mph (pretty fast to me for my pontoon).

Does this sound like it's time to rebuild the carbs. The only thing I can figure is that there is some trash that got sucked up and was blocking the high speed jet an then it broke loose.

Another question. Should I have air filters? It looks like the spark arrestor has holes for something like an air filter to be bolted up but I have nothing.

 

[hidef]

Re: Time to rebuild the carbs?

No air filter used on an outboard as there is not a lot of dust to be found on the water. If the carbs haven't been cleaned in a couple of years they are most likely due. Plus if you are using gasoline with ethanol the alcohol as probably deteriorated your fuel lines which is what has plugged the high speed jets in the carb. Also you might want to replace the water impeller while your at it.

 

[clemsonteg]

Re: Time to rebuild the carbs?

Well that was part of the reason for changing the fuel lines because I didn't know if they were alcohol resistant and I'm sure it has seens some ethanol. I just got the boat this season and the last two fill ups have been with ethanol free 87 octane I found locally. I guess I will rip into them this week. Anything special I should know? I have done carbs on lawnmowers, weed eaters, and 4 wheelers before. I imagine this can't be much different.