More power from a F100A

[Rob M]

Hi all, my first post and good to see a forum dedicated to Yamaha.

I have a flats/bay boat which is 18'2" and weighs somewhere around the 1400lb mark. Driving it is a 2004 F100A 20" (carbed) motor with 150hrs, while it runs very well at 40mph with two people and about 20-30 gallons of fuel I now wish to go faster?

The prop is a Solas 19p, 4 blade SS and pulling around 5600rpm

Is there a performance modification that can be done to the motor or does it really require a HP upgrade, like a 115hp.

Any advise would be appreciated

[Ken]

Rob,
I would say that F100 is doing a great job if you can get 40 mph with that much weight. I have a Pathfinder that weighs 1100 pounds with a Yammie 2-stroke 115 and with two people on board I can only get 45 mph.
I would not try to modify that F100 - you would be better off repowering with more hp outboard.
Good luck,
Ken K

[Rob M]

Thanks for that Ken, for a while the most mph I got out of her was 44mph swinging a 21pitch but I was advise to put a 19 pitch. While the F100 is a fantastic motor and I love it, it just lacks the omph of a 2-stroke. Would you suggest a 2-stroke or a F115hp, or even a F150. The hull is rated to a 150hp and the recomended is a 115.

The boat is a Flycraft

Thanks

Rob

[Ken]

Rob,
Since the 4-stroke is heavier than the 2-stroke, I would go with a 2-stroke 115 (130 if it is still available). If you want to stay with a 4-stroke, I would go with the F150. I don't think stepping up from F100 to F115 is going to get you much. This is all personal opinion, for I have not tested any of the 4-strokes - this is just a gut feel from my experience with my C115 2-stroke and what I have read from others.
Go to another forum at maverickboats.com and do a search on the 4-strokes performance on various boats/weights. That will give you a little better feel for what you are looking for.
Good luck,
Ken K

[Rob M]

Cool thanks for that Ken.