F90 -65 Jet Slight hesitation at just below WOT

[Kanadakid]

Gents

I'm new to this site and have enjoyed reading all the posts about Yamaha outboards.

My issue is this ans it's more of an annoyance than a critical problem.

My engine starts really well and run through the power band and RPM range.

I normally start off by gradually running up to full throttle, not slaming it dowm, and they one at full speed drop back on the throttle a little to 100 to 200 below WOT. I find that this save a lot of gas and only loose 3 /4 MPH.

At this power band just below WOT I get slight hesitations. I can feel the boat slightly slow down and the RPM guage drops maybe 50 for just a second. It happens every miunte or so.

At wOT it seems to run fine and at lower RPM's 4000 , 3000 also runs fine.

I have a Tempo 10 micron water separator filter, I always keep stabil in the gas and run Ring free. There has never been any water in either fuel filter.

I put NGK iridium plugs in a month or so ago.

Any thoughts ?


Thanks in advance for help,


Kid

[boats.net]

If it's only a 50 rpm flucuation it's probably just the timing moving up or dowm
n a degree, which if it's a newer model with fuel injection there would be little or nothing you could do to even it out except slow down or speed up to get it past that spot. However I couldn't say for sure if it is the timing without test running it.

[Kanadakid]

Thanks for you thoughts. It is a 2003 F90 so it is carbed. I can't imagine with all the precautions that I take that it could be related to the carbs.

2 filters, connstant stabil in fuel. never sit for more than 3 to 4 weeks without being run and ring free.

It is very slight hesitation but noticeable and annoying.

Thanks again,

KId