Yamaha F 90hp outboard 4 stroke - fuel injected WOT question

Dmonnny123

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I have a 2008 Yamaha f90hp with 135 hours on it. I just bought the boat (2008 2275 rli)

At full throttle with me alone it's at 6400-6600 going 25mph

This is the prop the guy I bought it from said came with it from the dealer. Boat is like new. Just think I'm supposed to be between 5000 and 6000 as the sweet spot at wot if I'm not mistaken on this outboard???
 
What prop is on it now?
 
I have a 20 SLX, and run 22 mph at 5700 rpm maxed out. 2013 70 hp Yamaha, 200+ hours so far
 
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My engine's redline is 6000 rpms, but it hits the rev limiter at 6300 rpms.

Your motor seems to be over-reving much more than mine.  What is your engine's redline?  I suggest you have your tachometer checked for accuracy.

A higher pitch prop may be in order.
 
Rpm's seem a little high. My 09 2075GLi with yamaha 90 was right around the 24-25mph mark. What prop are you running? I'll see if I marked down my prop somewhere, I think it was 13" 13 1/4? Could be totally off, that number is just in my head for some reason.
 
I suspect the tach is not set properly. Most engines would be hitting a rev limiter before 6500, assuming the smaller ones have one.
 
Thanks all. I'm out of town for the weekend but I'll check the prop when I get back home. How does one test the rpm gauge?

I figured it should have a rev limiter as well... And it certainly isn't hitting that. When pinned it stays or at least says 6400-6600
 
Thanks all. I'm out of town for the weekend but I'll check the prop when I get back home. How does one test the rpm gauge?

I figured it should have a rev limiter as well... And it certainly isn't hitting that. When pinned it stays or at least says 6400-6600
It depends on which tach you have, digital, analog, multifunction, etc. Some of them have either a switch on the back to set the number of pulses or extra terminals to do the same. Others are just positive, negative, and pulse. It likely would have been rigged properly to begin with, but your dealer can verify it.
 
Now I'm all confused.... Not sure what to do.

The retired couple I purchased the boat from got it at the dealership brand new in 2008. They said that's the prop that came with it from dealership. Since then they've only put 136 hours on it. It's immaculate. That said, what do I do now?

Is it my rpm tach? Is it the prop?... The rev limiter isn't hitting. How do I test this? Do I have to take it to dealer? Such a pain as I have to rent a trailer, haul, etc...
 
See if there are any independent boat mechanics in the area that do house calls.  It's just so difficult to deal with a boat if you don't have a trailer.  You really need the rpm's vs tachometer reading to know what to do about your prop.  If it's accurate you need a pitdh 3-4 inches higher.
 
Ok so out in the boat now. Alone

Here's the specs.

Full throttle. Going 24 mph. Rpm at 6800

The prop appeares to say

13 5/8 x 13 - K

It's a white prop. This is with trim medium
 
Ok now I'm really confused. Turned off the boat and then let her run full throttle for a little bit and now it's perfect

6000 rpm 24mph wot.

And it's doing that everytime all the time. Super strange. Did it just need to be ran a little bit after the winter?? So odd.
 
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