Hydra Sports CC 22' & Yamaha F150TXRC 2005 Prop?

[rdefrei2]

Hi, recently I've changed the lower unit of my Yamaha F150TXRC 2005, bought a SEI one which they say has the same gear ratio 2:1 but unfortunately my boat which is a 22' HydraSports Center Console 2004 is now running slower and I'm getting less RPM. Also it's taking a long time to plane, I was riding with 4 people on it and had to ask some of them to move to the front of the boat or it would not plane and RPM would stay @ 3200. I'm using a 14 1/4" x 19P Aluminum Prop which is in bad shape I believe. My concern is how I was used to run fine before I changed the lower unit and now is so bad? Could be the Prop that's doing that? My engine was running top speed 34mph and RPM 4800 before changing the lower unit, now I'm getting top speed 31mph and RPM 41000 but to get the boat to plane is almost impossible if someone is seated on the back of the boat. I definitely decided to change the prop to a new one.

Could someone give me some advice?

Thanks,
Roger.

 

[steelespike]

Your motor wasn't reaching the correct wot rpm in the first place. Assuming a light load your wot rpm should be about 6000.
I do think you have a motor issue.At your original 4800 wot it would require a 5" pitch reduction to reach about 6000.Putting you at about a 14" pitch
That's a size for a pontoon or other hard to push boat.
Thus the suspicion of a motor problem. There aren't enough prop sizes to make up for your present 4100 rpm.
Your problem could be as simple as a plug wire off or poorly adjusted throttle.
Hopefully a healthy motor will at least partially solve the rpm problem.

 

[rdefrei2]

Interesting, my boat never reached over 4800 rpm since I've bought it. Also the mechanic that replaced the lower unit run the boat on a lake and didn't find any issues with the engine saying everything was fine and good to go. I will have to get back to them to check again I guess.