Prop help Zodiac Yachline 340DL with Yamaha F25

[zigzag930]

Sure would appreciate any input on the correct prop for this combination.
Currently there is a Powertech 10"x11 stainless 3 blade prop on the F25. Motor has a new Dol-fin and is mounted on the very upper holes (as high as it can go without a jackplate)

With one person onboard and full tank of fuel @ WOT engine RPM's are about 5500. Boat planes ok, but bow rises to the sky with one person sitting behind the console. With a second person sitting in the middle seat area, boat planes better, without as much rise and runs about the same RPM on the top side.

With three adults on board, I can not get this boat to plane. RPMS won't go over 4000 and boat speed is approx 8 kts. Feels like the boat is right on the edge of coming up on plane, but never gets there. I've moved people around, but that doesn't help.

Tubes are new and are properly inflated. Gear onboard include 10 lb for 2 anchors, fuel 8 gallons, battery, GPS, lifejackets, 5 lbs of tools and battery tender.

I was considering a Solas HR Titan 4B 10x10 pitch prop to gain better bite and stern lift. Thoughts? Comments?

Thank you

 

[QBhoy]

Hi. I’m afraid that your issue is quite a common one. Not easily figured out unless one is familiar with the behaviour shown after messing with many configurations of boat size and engine size combinations over the years.
So basically what is happening here, is that the fairly short boat length you have, hasn’t much planing surface area or enough length to encourage planing..to the point of overcoming the rather heavy engine sat on its very rear. Believe it or not..the same engine on a boat like yours, but only say, half a metre longer, would plane much easier with the same engine and people on board. Your short hull with little surface area in the water to displace the load…actually hinders things, compared to a boat slightly more able to spread its weight better. Props have a small chance of helping or lessening the issue perhaps, but the solution is usually a lighter engine or better management of the weight onboard. More weight on the tubes can help a little.