1988 70hp Yamaha bogging down

[scottmcpherson]

I have an older (1988) Yamaha 70 hp outboard. Ran it about 2 months ago and ran like a top. Took it out today and starts right up but bogs down when trying to run. I moved weight to the front of the boat and manage to get up on plane. Top end ran pretty good. I assumed it was some water in the fuel so I would burn it out on the top end. Ran for a bout ten minutes, came back off of plane and motor dies. Started back up and again motor bogs down. Go through the same scenario about four times and finally just give up, didn't want to risk burning up a piston if it was not getting proper lubrication. Anyone have any idea? All new fuel line and connectors. While out on the water swapped fuel tanks also.

 

[robert graham]

It's a good bet that there is some trash/debris in the carb jets....need to be removed, disassembled and cleaned.....If it was me I'd pay an experienced Yamaha technician to do this, but lots of folks do it themselves....but of course there are parts to order, methods to apply and a learning curve involved. Give strong consideration to the installation of a fuel/water separator type canister filter on your transom, if you don't already have one. Also the consistent use of a fuel stabilizer like Stabil in your fuel tank is excellent preventive maintenance.

 

[scottmcpherson]

All I have filter wise is the small filter that is attached to the motor. I always use the ethanol stabil and most times I have the tank full to keep condensate down. If the boat runs at high RPM it could still be a plugged jet? Also forgot to mention in first post, right after I ran pulled cowling and had gas leaking from middle carb. could not tell where it was coming from though, kinda looked like it was coming from throat of the carb. Guess I can do some experimenting.
Thanks for the suggestion.

 

[99yam40]

if fuel was coming out of carb then you have trash holding the needle from sealing into seat or float has a problem and not setting needle into seat

 

[scottmcpherson]

I've seen stuck float before, this did not look like an overflowing float chamber. Might have been though. I will tear into the carbs and see what I find. Thanks for the help!

 

[robert graham]

Just to check for something....drain each carb float chamber onto a clean white rag and look for dirt particles, water, other debris....may give you some idea of what's in there. I drain my carbs several times per year and especially for extended motor lay-ups of several weeks or months....those jets a real small and don't take much to plug one up!....I can drain the carbs on my 90HP Yamaha easily in 5 minutes....

 

[scottmcpherson]

Pulled the carbs today. There was some varnish build up but nothing real bad. Might have been enough to cause the problems. Will check it out next week to see.
Thanks again for the advice.