Thread: Prop and Jack Plate questions????????

I got the recommended pitch prop (21) Solas 4 blade for Yamaha 115 four stroke and also added a jack plate for SI clearance issue. This past Friday, I finally got enough time on the new Yamaha to give it a shot of WOT. Only get about 4900 rpms and that was with lots of up trim.

I don't know crap about this stuff. I don't wanna screw up a new engine.

Suggestions?????????

Really depends on what kind of boat you have, on performance boats the higher you can run motor the better, this will also bring RPMs up. The real limiting factor on how high is the water pressure

I was running an 18 foot Wellcraft Sportsman with a F115 and it ran 6000 RPM's WOT. I think I was running a 13 3/4 x 17 Stainless steel prop. I'm sure my Wellcraft was alot heavier boat. I think 4900 Rpm's is lugging your motor though.

Tom, I believe your motor should be turning 5500 at WOT but I don't have any documentation on Yamis. Check your owners manual and see what is recommended or perhaps TMD or Scrapper can verify what I'm saying.

Originally Posted by Shellback

I was running an 18 foot Wellcraft Sportsman with a F115 and it ran 6000 RPM's WOT. I think I was running a 13 3/4 x 17 Stainless steel prop. I'm sure my Wellcraft was alot heavier boat. I think 4900 Rpm's is lugging your motor though.

I have the 861 Predator by War Eagle....

had a skeeter with a f150 and got 6000 (max rpm) with a 21. i would think a you might want to try a 19

Cane Pole, I'm running the same prop on the exact same boat with very good results, 5,600 rpm @ 54 mph with the speedo. My only thought might be the jack plate height or if not that then maybe the way the load is balanced? If you want to call 318-455-0745 I'd be happy to help if I can. paw paw perch

Originally Posted by paw paw perch

Cane Pole, I'm running the same prop on the exact same boat with very good results, 5,600 rpm @ 54 mph with the speedo. My only thought might be the jack plate height or if not that then maybe the way the load is balanced? If you want to call 318-455-0745 I'd be happy to help if I can. paw paw perch

Your results was what I expected. Do you have a jack plate? It was Paul and I in the boat. Prob 500 lbs. together. 3 batteries. 1/2 tank gas. A few fish in the front live well.about 1/2 full of water. Not really over loaded. Boat has good hole shot. Immediately on plane. Doesn't have to groan to plane out.

I don' have a jack plate and thought my prop might need to be lower and considered putting one on but have decided to wait.Where is the cavitation plate in relation to the lowest point of the hull on your boat?

Originally Posted by paw paw perch

I don' have a jack plate and thought my prop might need to be lower and considered putting one on but have decided to wait.Where is the cavitation plate in relation to the lowest point of the hull on your boat?

Not sure. Boat is at the lake about 40 miles from where I "stays". Look at my Ram mount post on main forum and you can see it, maybe. Ima lost stepchild with this stuff.