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Where do you trim to?

Where do you trim to?

Old 05-08-2010, 12:29 AM
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Originally Posted by DonRoc View Post
you want to trim for ride quality and speed but not RPMS, you prop for RPMS. If you are trimming up to get more rpms you are just adding slip not speed. If as you say "I have an unusually high X dimension to boot". Then positive trim will have less effect on bow lift and just slip as you trim much past neutral. my boat runs best just slightly positive (up) from neutral all tested by GPS. What are your rpms and speeds on the props you tested? what rpms does the motor make max HP (if you know)? i agree with johnny call [email protected] have your credit card ready and just do and order whatever he says. I would guess if slip is ok, a bravo 1 would work best with a hight x giving some bow lift, if slip is bad a 5 blade will be necessary. Let us know what you come up with
I have SOME of that information for ya Doc. I don't have my boat in front of me, therefore I can't measure my x-dim. We ran a double Mercury 32 double labbed prop, turned 5900rpm for 89mph. The video of this run can be seen here http://www.youtube.com/watch?v=0IO0Dujxs90 . Our second run was unsuccessful. We turned a BBlades labbed 30p only 5200rpm at 82mph. Motor makes 619hp I believe. Fuel and passenger numbers were the same. Here is an attached picture of the transom. I'm hesitant to call BBlades. I'd hate to drop $750 on a prop and not be exactly what I need. I would much rather find the right stock propeller, THEN send it to BBlades. Therefore I at least have a base platform. My mechanic said 5900 rpm is fine and the motor will live longer. I believe that 6200-6300rpm is the correct range for this motor. He's going to send me a dyno sheet on Monday or Tuesday.
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Old 05-08-2010, 10:48 AM
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I put my ruler on the picture looks like 3" below, lol, bet im close.
Ok the slip numbers are off the chart 25% with the 32. and reasonable with the 30, 16% that's about where mine runs 15% or so with a Bravo 1 style prop. I wonder from your other post that you were over trimming the 32 to get the RPMS like I mentioned just adding slip.
I was about the same hp as yours and ran a stock bravo 1 30p @ 5700rpm and 90mph.
Are your mph numbers all GPS? sounds like you might want a bravo 1 28 to get the rpms up.
I would disregard the numbers from the 32 it does not make any since. my hope is you speedo is not GPS then I could explain everything, 1 you way over trimmed to get rpms, and the angle of the drive caused the Speedo to read high. I used to do it with a stingray i had, I could peg the speedo over 80mph with a lot of over trim but the gps said closer to 65, I would put the trim back down the speedo would read closer to 70 and the gps said 71-72... Lets hope that's your problem, then we can start from scratch with the 30 from bblades. I would guess you should run 85mph.
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Old 05-08-2010, 11:32 AM
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Originally Posted by DonRoc View Post
I put my ruler on the picture looks like 3" below, lol, bet im close.
Ok the slip numbers are off the chart 25% with the 32. and reasonable with the 30, 16% that's about where mine runs 15% or so with a Bravo 1 style prop. I wonder from your other post that you were over trimming the 32 to get the RPMS like I mentioned just adding slip.
I was about the same hp as yours and ran a stock bravo 1 30p @ 5700rpm and 90mph.
Are your mph numbers all GPS? sounds like you might want a bravo 1 28 to get the rpms up.
I would disregard the numbers from the 32 it does not make any since. my hope is you speedo is not GPS then I could explain everything, 1 you way over trimmed to get rpms, and the angle of the drive caused the Speedo to read high. I used to do it with a stingray i had, I could peg the speedo over 80mph with a lot of over trim but the gps said closer to 65, I would put the trim back down the speedo would read closer to 70 and the gps said 71-72... Lets hope that's your problem, then we can start from scratch with the 30 from bblades. I would guess you should run 85mph.
It's a GPS Doc........
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Old 05-08-2010, 06:35 PM
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Dyno numbers are useless unless the correction factor is set properly. We can take a 525 and make a 600 hp motor without touching the motor at all, and easy. Not saying your motor isnt a 600 hp motor, but it can happen. Either way call bblades !!
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Old 05-08-2010, 07:45 PM
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Well you have the hp if you are able to run 89, the good thing about dyno numbers is you can prop to peak hp even if that number is slurred due to correction factor its still going to make peak at that rpm.
I assume both test were same day same conditions. Then again throw out the 32 numbers and try a 28. Possible the motor is making much more power at the higher rpms. with a reasonable slip number a 28 should run near 90 @ 5900. i think you need some new baseline numbers and try some known props and go from there.
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Old 05-24-2010, 12:35 AM
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Ok, found out some interesting details this week. Called up BBlades and he said my prop is NOT a BBlades propeller. It is in fact, a labbed Mercury propeller. Going for another ride on Tuesday with a stock 28 B1 and hopefully maybe a stock 26 as well. My goal is to find the right stock propeller within 200 to 400rpms of my goal, then bring it to a local prop shop and have them lab it for acceleration and the remaining 200-400rpms. I'll keep ya'll updated.

Last edited by Mastercraft240; 05-24-2010 at 12:37 AM.
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Old 05-31-2010, 06:52 PM
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How did you make out? Just curious if you ever tried the 28....

My propshaft is parallel with the bottom at #4 on my indicator. That is the sweet spot. Any more and the rpm's climb but speed drops off. Any less and both rpm's and speed drops.

Last edited by jdub; 05-31-2010 at 06:55 PM.
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Old 06-01-2010, 10:41 AM
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Originally Posted by jdub View Post
How did you make out? Just curious if you ever tried the 28....

My propshaft is parallel with the bottom at #4 on my indicator. That is the sweet spot. Any more and the rpm's climb but speed drops off. Any less and both rpm's and speed drops.
The power steering belt spun off..... I don't know how it loosened up within the course of our 30 second ride. My guess is on take off. I felt the boat torque left pretty hard and I knew something was wrong. When we came to a stop, I opened up the engine hatch....looked at my dad and said "I think I found the problem". It was the belt at the bottom of the bildge floating in about a foot of water. Every time we ran the engine, we had water leaking into the bildge. We had about a foot of water pumping out at all times. It took about a solid minute to drain all of the water out once we got the boat on the trailer resting on a downward slope of the ramp.
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Old 06-01-2010, 11:53 AM
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That's not good. Can you see where the water is coming from?
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Old 06-01-2010, 05:06 PM
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Damn, you just cant win with this boat huh?

You wil have to run the boat with the hatch off, or open a bit so you can watch. Could have nicked a hose that is only spraying water out under pressure.

Oh, and I usually trim to about 5 on the gauge, which is a tick past neutral, but have found that adding some more trim increases slip and RPM, but also speed. I cannot trim enough to where the boat becomes unstable or to where I really start to blow out.
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