Re-Powering From a Yamaha F60T

[corruptibleseed]

Hi everyone,

I'm currently running a Yamaha F60T on my 22' skiff. The engine has been excellent and is now approaching 2,400hrs. I've followed the service manual religiously.

I am now thinking of repowering the boat. A key objective would be to improve the fuel economy as I currently cruise at just under 5,000rpm.

I have two questions:-

1. How far above the waterline does the exhaust relief port have to be? If I upgrade to a F90, the bigger motor weighs an additional 99lbs or so. I have attempted to simulate this weight by sitting on the cowl with my dog. Together, this is about an additional 220lbs in weight. With this additional weight, the lower exhaust relief port is still about 3.5" clear of the waterline and upper one is about 7". Is this sufficient?

2. I understand the F90 and the F115 share the same block. The bigger engine has dual overhead cams and weighs about an additional 22lbs. I'm still waiting on the price difference, but how much improvement to the fuel economy and handling (if any) will I see by going to the bigger, heavier and more expensive motor?

Thanks so much!

[99yam40]

your best bet is to find the Yamaha performance bulletins for boats like yours with the different motors to compare them
pay attention to what props were used during those also

this may help you find them
Performance Bulletins - Yamaha Outboards

[corruptibleseed]

Thanks, 99yam40. That's a great suggestion... been looking through the bulletins!

[boscoe99]

[corruptibleseed]

Thanks so much, Boscoe99, that is very much appreciated. Sorry for the delay in responding; just been a little caught up in a few other things.
That's very useful info. Perhaps I was just worried about nothing because I definitely have more than the prescribed 3.9" clearance between the water surface and the bracket seating point!
I have also recently spoken further with my local Yamaha dealer who also believes that there should not be any issue, so hopefully it will be all good!
Thanks so much again!