2010 90hp Mercury Outboard power loss issue

[lindy_rig]

I am having some issues with power loss on my Mercury. It comes out of the hole fine and mid throttle is good but once I get to the top end about 36-40 mph, I can hear the motor drop power almost as if it is bogging down. It's not to the point where it really slows me down but, I've watched my speed drop about a mile or two p/h, but then it comes out of it.

I brought it to the dealer where I got it from and they said it was bad gas. I have ran 2 tanks of non-oxy fuel through it now and am still haveing the same issues. It isn't constant but happens atleast once when I have it out.

Any advice or thoughts?

[BoxMN]

Is this 4 stroke or two stroke? I am guessing four... But on our 2 stroke 90hp years ago (a 1987), we had similar symptom, and it ended up that we needed to swap to a hotter plug than specs called for, and it went away.

Have you changed plugs yet? Not sure plugs would do that, but many people don't change plugs unless they have problems, even though it would be a good thing to replace plugs at least every other year, every year if used a lot (100 hours).

Good luck.

[boatfixer]

Fuel filter?

[lindy_rig]

It is a 2 Stroke.

Thanks for the replies....I do have a set of new plugs that I am going to try. The plugs that are in there now are the flat type (not sure if there is a specific name) and someone told me they very rarely go bad.

boatfixer...I'm not what you call mechanically inclined, is the fuel filter an easy replacement on these motors or is it something I would need to bring to a dealer?

[boatfixer]

At this point I'd suggest taking it in. There is a filter in the fuel vapor separator. If you are unfamiliar with some of this, it just might be better to have the correct diagnosis made by a good tech.

[lindy_rig]

If the new plugs don't fix it, that is what I will end up doing.

[delcecchi]

I had a 115 two stroke that did the same thing for years. Dealer couldn't figure it out. Thought it was running rich for some reason but didn't want to go smaller jets than recommended. (I don't blame him)

It was like an intermittent miss or 4-stroking at 3800 to 4000 rpm steady speed. Jiggle the throttle and it would go away.

Cure was a Suzuki 4-stroke.

[tlbigstump]

Just a thought but are you maybe touching the rev limiter. It will sound like a high speed miss. Try adding some extra weight to the boat like another person, or something and see if it goes away.

[delcecchi]

Mine happened at around 4k rpm, maybe 3800. Not a rev limiter problem.

[tlbigstump]

I was refering to the OP Del. He said at top end.