What is your oudrive depth? - Page 6

tcuda499 · 11-19-2009, 10:35 PM

Quote:

Originally Posted by BenPerfected

Lowering the drive shaft height or adding blades will likely scrub speed but either will make it easier to get on plane. I believe that a 38' boat w/5-blade props will also significantly increase the chance of Bravo Drive failure due to reduced prop slip. Using your tabs and breaking the props loose is a sign to me that you set up is close

With 5-blades, you might see + 1-2 MPH...is it worth the extra drive stress?
Consider trying a set of B1 28P. They should make it easier to get on plane and you may pick up a few more HP with improved acceleration.

Thanks,
the boat had 26 bravos when in Az. owner stated it ran 75-78 at 5700 rpm. 28's might be the way to go. but would smaller pitch props be easier to blow out while trying to plain?

BenPerfected · 11-19-2009, 10:46 PM

I would say it is the other way...the 30P will blow out sooner as the are tying to grab more water while pushing the same weight.
B1 28P should be easy to borrow for a quick test. If you like the result, you might be able to trade someone on OSO.

tcuda499 · 11-19-2009, 10:50 PM

alright, will try.

jeffswav · 03-15-2010, 09:42 AM

ttt Thought this might help the guy asking about a shortie.

jeffswav · 05-24-2010, 12:42 PM

I wanted to update the post and give my results. I raised my engine and drive up 3". Propshaft centerline was 8" now it is 5". I gained a solid 5MPH just by raising the drive. The boat rides better, flatter and faster with less trim, cuts through the waves much better. Planes off with a Mirage prop and still had 30 PSI of water pressure. Best speed of 74MPH @ 5200 RPM with 25 pitch Mirage plus lab finished with double cup. That is 9.8% prop slip, I have a 26p Bravo I can try but I do not know if any other prop will do better than that.

steveh1209 · 05-25-2010, 12:41 PM

Quote:

Originally Posted by jeffswav

I wanted to update the post and give my results. I raised my engine and drive up 3". Propshaft centerline was 8" now it is 5". I gained a solid 5MPH just by raising the drive. The boat rides better, flatter and faster with less trim, cuts through the waves much better. Planes off with a Mirage prop and still had 30 PSI of water pressure. Best speed of 74MPH @ 5200 RPM with 25 pitch Mirage plus lab finished with double cup. That is 9.8% prop slip, I have a 26p Bravo I can try but I do not know if any other prop will do better than that.

I am right at 10% slip with my 232. 600hp stock prop depth of 7.5". I will be raising with a -2 later this season. Be nice if I saw 5mph more. That would put me low 80's and I'd be happily done then. Now 78mph @ 5250rpm with 25M+. Have to over trim a bit for that though.

jeffswav · 05-25-2010, 04:03 PM

Quote:

Originally Posted by steveh1209

I am right at 10% slip with my 232. 600hp stock prop depth of 7.5". I will be raising with a -2 later this season. Be nice if I saw 5mph more. That would put me low 80's and I'd be happily done then. Now 78mph @ 5250rpm with 25M+. Have to over trim a bit for that though.

It seems to equate to about 2MPH per inch. You should gain 3 to 4MPH, I would try the prop you have now first. I still have a little work to do to hit 80MPH.

AIR TIME · 05-26-2010, 07:58 PM

just waiting for my motor still for the saber its drive height is set at 3'' if we set the konrad ace up right

, hope to have motor by next week

since the new boats been here for almost 8 months. so maybe by aug I will have some test ## shooting for 100 plus. and my 24 ol ran flatter with the higher drive height too. I may have to steel that motor but it will be slower.

jeffswav · 06-03-2010, 09:18 AM

ttt Maybe this will help.

BenPerfected · 03-27-2011, 09:07 PM

Quote:

Originally Posted by jeffswav

I wanted to update the post and give my results. I raised my engine and drive up 3". Propshaft centerline was 8" now it is 5". I gained a solid 5MPH just by raising the drive. The boat rides better, flatter and faster with less trim, cuts through the waves much better. Planes off with a Mirage prop and still had 30 PSI of water pressure. Best speed of 74MPH @ 5200 RPM with 25 pitch Mirage plus lab finished with double cup. That is 9.8% prop slip, I have a 26p Bravo I can try but I do not know if any other prop will do better than that.

If you can still get on plane with the Mirage 25P there is likely more MPH left. In our testing with twins we ended with +10 MPH moving from -5" (with Mirage 27P) to -2" with Bravo 28P. 3 of the 10 MPH was due to the efficiency of the IMCO shorty case.