Tomcat prop question

Pescador2 · Posted: Fri Sep 25, 2020 5:11 pm Post subject: Tomcat prop question

I have a2007 tomcat with twin Suzuki 150 hp motors counter rotating prop on starboard engine permatrims installed 3x16x21.5 SS props I am generally very satisfied with performance ...3200rpm 21-22 mph. 3800 rpm 27-28 mph 5100-5200rpm 42 mph. Primarily Fresh water use. I am considering going to a 4 blade to achieve a lower plane rpm as well increasing wot rpm to increase wot speed ....I have found a Suzuki Water grip 4x15.25 x22 SS prop.....what can I generally expect going to a 4 blade and is the above 4 blade a good match...other recommendations

thataway · Posted: Fri Sep 25, 2020 7:03 pm Post subject:

Is your WOT the 5200 RPM and 42 MPH? We had a 4 blade Power Tech (I believe) and our WOT light boat was almost 50 mph at 6,000 RPM. I am not positive about the pitch, I may have the build sheet and can check. I believe it was 19 or 20 inch pitch.

You need more RPM, and putting on a 4 blade, with more pitch will actually lower you WOT RPM. You are lowering the diameter slightly--My best guess is that you will not get the increase of RPM--but I don't know the cup and rake etc of the "Water Grip" props. A 4 blade does give more stern lift and more low end performnacnce out of the hole, But generally 3 blade props are faster.

You also want the Props to rotate in, which you have. --instead of out as a normal twin screw. The motors have to be set at proper height, so you just see the top of the antiventiallation plate when on a good plane.

I found that Permatrims didn't really help the plane at lower speed--they thru a lot of water, and were almost counter productive. I had put them on attempting to get a lower planing speed.

Pescador2 · Posted: Fri Sep 25, 2020 8:39 pm Post subject:

Yes 5200rpm 42mph medium weight in boat. Motors trimmed up Antiventiallation plate at water level on plane I did notice more stern lift with permatrims water rises up on motors a bit more a lower speeds And they throw more water. I cruise mainly on Lake Superior with short wave sets so I’m mostly attempting to keep on plane at lower rpms I do understand that 3 blades are faster not a big issue as I Seldom cruise at wot ...however it’s still puzzling why I can’t get over 5200 rpms At wot? Ideas? Sounds like your 4 blades Are what I need. Thanks for your response Joe