Sporadically reving up and down at WOT

[jhamill1986]

60hp 83' Mariner 60e 6F0 L 305764. I'm a newb to the outboard world so bear with me. after about 30 seconds at WOT the engine starts reving up and down sporadically and then dies if you bring it back to idle. Usually have to run mid-throttle to get back to the ramp before it dies all together. also i hear some faint knocking whenever i have to limp it back to the ramp but dont hear it when its on plane. Problem just started during 5th time out on the water since the carb rebuild (i had no problems prior except for plugs fouling and idle adjustment) but it has always started back up after sitting for a while. now it wont start at all...even on the muffs... During this time i did a spark plug test and each plug is throwing a very strong spark. The motor sat up for ten years and i have rebuilt the carbs, cleaned out gas tank, replaced bulb and hose going to the gas tank, changed spark plugs, changed lower gear oil and impeller and ran seafoam through it. The problem just started with it reving up and down like that...the only problem i had previously to this was the plugs fouling every ten minutes due to excess carbon which i have recently fixed with a can of quicksilver engine cleaner. Maybe this has something to do with it (dont remember exactly what its called but it certainly cleaned my engine and made it run a lot better in the water at idle and mid throttle speed - plugs stay very clean now and engine goes into gear very easy at the lowest idle setting) oh and pumping the bulb does not affect idle speed nor does it help when the engine is going crazy at WOT. Ive read a lot on this site and cant quite find anything similar to what my engine is doing. I'm thinking something electrical. any help is appreciated!

Thanks,
Joseph

 

[jhamill1986]

Re: Sporadically reving up and down at WOT

Update!

The engine is now running on muffs. I put seafoam in the tank and it seems to run a lot better now... I havent taken it out on the water but i will today after work. Question... I believe it was water in the carbs causing this since the seafoam made a big difference. But how does water get into the gas in the first place? It hasnt rained or anything and the tank's vent is always closed when not in use. is it condensation? and How do i prevent this from happening?

 

[bboy57]

Re: Sporadically reving up and down at WOT

keep tank full and/or use stabil or other water remover

 

[jhamill1986]

Re: Sporadically reving up and down at WOT

ok still doing the same thing after about a minute of WOT then runs terrible all the way back to the ramp and eventually dies and cant get it started until i wait a while. Could it be the Coils getting hot?

 

[jhamill1986]

Re: Sporadically reving up and down at WOT

anyone?

 

[jhamill1986]

Re: Sporadically reving up and down at WOT

Well i guess i stumped everyone. ill be dropping it off at the boat mechanic and posting the outcome.

 

[jhamill1986]

Re: Sporadically reving up and down at WOT

well the boat mechanic had about a month waiting list so i decided to look back through the carbs myself. turns out that both the carbs werent seating correctly at times causing an overload of fuel. i removed the floats and seats and blew out the passages with carb cleaner. Took it on the water yesterday and ran like a dream. Now my only question is how can the fuel filter be clean but the carb bowls are filling up with trash? because the carbs were just rebuilt not even a month ago and the bowls were cleaned out. Could a failing Fuel Pump be causing the debri?

 

[sparticus]

Re: Sporadically reving up and down at WOT

What kind of trash? Do you run gas with ethanol? I know some have had problems with the ethanol breaking down the rubber on the inside of fuel lines. I know they have had to get fuel lines that were compatible with the alcohol. Something to ponder.

 

[jhamill1986]

Re: Sporadically reving up and down at WOT

Thanks for your immediate response and ill try the alcohol resistant fuel line.

 

[jhamill1986]

Re: Sporadically reving up and down at WOT

Since i'm replacing all the fuel lines i figured it would be as good a time as any to either replace or rebuild the fuel pump. A few questions. Can anyone tell me the year of my engine? The model & serial are in my first post. Also i have learned that NAPA carries older outboard engine parts and would cost me a lot less than some of the other sites and i just need to provide the correct year. If i cannot find the Rebuild kit could i just replace the Diaphragm? i found a diaphram for about 14 bucks. Or would it be worth the time/money to just buy a whole new fuel pump which i also found for about 60?
All help is greatly appreciated. This site has helped me fix everything on my boat and its just about ready to fish. Thanks so much!!