Johnson 90 hp v4 misfire and power problem

[ARTandWATER]

year 2004 motor
model J90GLSRM

starts fine.
runs smooth to about 25 mph , then somewhere above that speed power cuts off and on; not a bog, feels more rough like a misfire.

pulled the plugs to check the gap since I just replaced them two weeks ago (checking the other person's work)
bottom port side plug had a bit of black on it.

cleaned the carbs
bottom port side a bit dirty, but nothing out of the ordinary

next thought is the Stator or Power Pack since the engine was underwater last year.
It is a summer camp's boat, and I did not work with it last year, so did not sink it or fix it when it sunk.

Anything else I should check?
Thank you.

 

[Daviet]

Re: Johnson 90 hp v4 misfire and power problem

Use an inductive timing light to check the spark on each cylinder when the problem occours, it will tell which cylinder is giving you problems or if is even an ign problem.

 

[ARTandWATER]

Re: Johnson 90 hp v4 misfire and power problem

Thank you.

That is a bit out of what I can do with my tool box. I'll see if I can get the clearance to take it to a shop.

Anyone else have idea?

 

[jonesg]

Re: Johnson 90 hp v4 misfire and power problem

Yes use a timing light as he said.
Any more questions?

You will spend at least 5 times the price of timing light if you take it in and you might get it back by october.

 

[ARTandWATER]

Re: Johnson 90 hp v4 misfire and power problem

thanks.
If it were mine, I'd be at it step by step. But, since I have about 100 people with opinions and a season that is closing fast, it needs to be in the shop. (essentially passing the buck)

The motor def. needed a larger fuel line, and a new fuel filter.
Both are on their way, and will eliminate any of the simple questions as well as make sure I don't lose power at full throttle.

Had a few people mention that metal tanks were a no no, something about an ethanol problem. Not sure what that's about, but I'll do some research here to see if there is anything in the FAQs (thanks for that link by the way)

The marina is going to work backwards, from coils, powerpack, to stator. Hopefully it's something before we get to the stator.
I'm keeping on top of them so there I can log it all for this boat.

as always, any other suggestions are helpful.
I'll also post progress as it happens so other people can get use from this.