3 blade to 4 blade
 

I recently went from 3 blade 23" mirages to 4 blade 23" Revolution 4, 4-blades(thanks Full Throttle marine:evilb: ). I expected a little bit of a loss of RPM's, and speed. I went from 66 GPS to 64.5, and 5000 RPM's to 4700 :eek: . Now for my question. Normally with the 3 blades I ran my trim best at 6 units. Today with the 4 blades I ran my trim up further, to 8 units then to 9 units, (full up trim using the switch on the throttle((Not using the trailer switch))) and I gained back my 5000 rpm's and 65.5 MPH. Is it normal to run the trim higher with the 4 blades than the 3 blades, and is this due to the stern being higher? Also, am I making the gimbal bearing work harder by running it that high?

IMHO, as a rule, yes!

I have found that a 4-blade prop provides more stern lift than a 3-blade due to the additional blade surface, and in the case of a Bravo/1, the increased diameter of the blades. With this flatter hull attitude, the additional drive trim is necessary to provide less wet surface on the hull and thus, more RPMs and potentially, more speed.

I can't speak to the gimbal question, but it would seem to me that it would be designed to accomodate any standard trim setting available.

StillHaulin you are correct. The 4B propeller induces increased stern lift, so more trim may be required to achieve desired bow lift.

Julie

WELL DAMNIT, I find out 5 days after the poker run. LOL. Thanks guys, Julie, still looking to lab them, figure my 5200 RPM goal is attainable.

You just let me know when your ready.

Julie

Tim,

I left you a voice mail.

I received it and left you a PM. LOL

Back at ya. The only thing we haven't done is talked via private email or met in person heheeheheh.

Talk to you later.