Engine Performance Issue, please help!

[Thomas Smith]

Changing the spark plugs has long been a fix for most Yamaha engine issues on these forums.

I repeat though that your plugs look quite out of the ordinary. I've never seen plugs like that. Something else is going on.

By something else, what do you think.....moisture in the plug well/tube? would this simply occur over time with condensation etc? or do you think something different? Thank you again for the help

 

[Stuntmanmike]

Condensation and time will rust any non stainless metal in a marine environment, twice as fast around saltwater..

 

[itsdgm]

How do the contacts inside the coils look? I agree with the other guys that the outside rust on the plugs looks unusual to me.

 

[Thomas Smith]

The contacts look great, no issues there at all.................

 

[Thomas Smith]

Update;

replaced the plugs and it ran fine with the hose to both engines in the driveway........throttled up and sounded good. Then went out on the lake to test it with a "load" to the engines. Ran like crap!! both engines and had exhaust smoke coming from the hatch then both engines died and never were able to get them to fire again. It never did run good enough to get it up on a plane or even a smooth low RPM.......always sporadic and ran real rough both engines......

Some thoughts.......now maybe change the fuel pumps and check filters in the pump assembly? Pump fuel out and replace ?? The fuel was full and I used stabile over the winter.............I am at a loss now....

Thanks as always for the advice and input.

 

[Jebinok]

I kinda feel like if it was bad fuel it would run like crap loaded or unloaded. but i would check for water in your tank i do feel like you have a supply problem. restricted, clogged, or sucking air ect ect
just my 2 cents

 

[Scottintexas]

if you have exhaust in your engine compartment you've got issues, it could be the exhaust fumes are choking the engine (we've seen that happen to a member before), try running it with the engine hatch open to see how it performs

 

[Scuba_ref]

The angle of the boat on the trailer can be different than in the water. If you have phase separation or water in your fuel it will settle at the pump intakes with the boat in the water and not necessarily so when on the trailer.

I went through this same issue a couple years back even though I used stabil.

 

[Thomas Smith]

Awesome, two things to try........Thank you more to follow !!

 

[Scuba_ref]

@Thomas Smith When I had my fuel related issues I ended up pumping out all the fuel from the tank. I also installed fuel/water separators (which some thought was overkill). Haven't had a problem since. The fuel I pumped out was milky white and thick!