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Please help me figure out how to drive my boat and get it on plane

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Old 09-16-2004, 11:45 PM
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Default Please help me figure out how to drive my boat and get it on plane

I 1st want to thank P4-33 Brian for advising me on my transmission problem. Now that I know the trans was not slipping, I have to figure out how to get this thing on plane. The boat is a 1980 flat deck scarab with turbocharged BBC and speed master II's turning 15x21 3 blade cleavers. Not sure how to measure the X dim, but what I have measured is the prop shaft centerline is 6" below the hull running surface. The speed masters are original to this boat and not lowers someone added to TRS uppers. This is a 475 HP turbo/speed master engine package. The port prop turns counterclockwise and the other, clockwise. I bought this boat this year and am learning about it all the time. this is the 2nd time I took the boat out and I am having problems getting it up on plane. I have tried all the combinations for the tabs and drives, tabs- all the way down or up, drives- tucked in all the way or trimmed out a little. Every time I slowly bring up the revs to about 3000, the port motor starts to cavitate (my buddy was watching) while I drove. I have tried easing back on the port stick and then on both, and I still get cavitation. I tried running up to 4000 RPM then throttling back then getting back into it again, result cavitation especially from the port prop ( RPM's jump up more than the starboard motor). PLEASE someone help me figure out how to get this thing to move out of it's own way.

Thanks
Pat Hughes
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Last edited by phughes69; 09-16-2004 at 11:50 PM.
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Old 09-16-2004, 11:55 PM
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Default Re: Please help me figure out how to drive my boat and get it on plane

Barring no problem with your prop pitch or drive height if you dig your tabs in hard,tuck your drives all the way down this boat SHOULD go on plane. It sounds like you've already tried this,any info from last owner/operator? Are you sure someone hasn't changed something critical to planing out (like drive length),Smitty
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Old 09-16-2004, 11:58 PM
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Default Re: Please help me figure out how to drive my boat and get it on plane

What happens if you just hold the RPM's at 5000 will it get on plane?
If I just raise the RPM's to 3000 my props slip also and the boat will not get on plane but if I go to 4000 it will slowly plane out.
What I usually do is just nail the throttle to 5000 RPM and the boat jumps onto plane.
The engines don't free rev but the props do slip some.
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Old 09-17-2004, 12:02 AM
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Default Re: Please help me figure out how to drive my boat and get it on plane

On my buddies twin 28 Pantera we used to have to turn it in a tight circle to get one drive to really bight to get it on plane. Definatley drives and tabs down.
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Old 09-17-2004, 12:04 AM
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Default Re: Please help me figure out how to drive my boat and get it on plane

Quote:
Originally Posted by Ryan Beckley
On my buddies twin 28 Pantera we used to have to turn it in a tight circle to get one drive to really bight to get it on plane. Definatley drives and tabs down.
Damn Ryan, Thats sounds like fun!!
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Old 09-17-2004, 12:13 AM
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Default Re: Please help me figure out how to drive my boat and get it on plane

I have a 36' Coyote (early Sonic) and I run them briskly up to 3300, (tabs up and drives all the way in) they start slipping a bit, rpm's go up to about 3600 or so and the boat goes on plane. I guess I could nail them to a higher power setting but I figure what they heck, it planes in about 3 or 4 seconds with this method. Someone please tell me that's normal because that's how I've been running them for two years now. Don't they all slip a bit coming out of the hole? How long's it taking you to get on plane with your tabs up drives in, a few seconds or minutes?
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Old 09-17-2004, 12:20 AM
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Default Re: Please help me figure out how to drive my boat and get it on plane

Try tabs LEVEL with boat.
Drives IN all the way.

rpms to 3000 and hold it there. If you don't see/feel gradual speed increasing, then feed it a few more revs. Should come on out gradually but I wouldn't expect a good hookup till you are running over 30mph.

Mirages style blades will probably work much better.
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Old 09-17-2004, 12:47 AM
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Default Re: Please help me figure out how to drive my boat and get it on plane

my dock neighbor has roughly that same boat, early 80's scarab panther. he has to bury the tabs and drives to bring it up on plane. spinning the same props as you but on trs's. he has to really "coax" it to bring it out of the water. i will see him this weekend ands ask him exactly what he does.
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Old 09-17-2004, 02:29 AM
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Default Re: Please help me figure out how to drive my boat and get it on plane

I had exactly the same problem last year before I bought Bravo one 4 blades.
The props at that time was 23" Mirage+ on TRS's

I had to rev to 2200, wait 15-20 sec for the the boat to catch up speed,
then very slowly go to 2400-2500, wait another 15-20-sec, then
VERY easy and slowly go to 3000 and let the boat do the job.
I could never force it on plane with those props.

I broke one of my 4 blades 60 miles from home recently, and borrowed
two 23" Mirage (old style, not+) just to make it back home.
Couldn't get it on plane with those props. I tried all the tricks from last year, it was impossible so I had to limp home at 8 mph.

I think 4 blades will do the trick, it worked for me.
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Old 09-17-2004, 02:43 AM
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Default Re: Please help me figure out how to drive my boat and get it on plane

Try the 4 blades, tabs down, drives in. With turbo motors you have to get the rpms up, at least 2500/3000 or maybe more. As the nose drops, slowly bring the tabs up to help bring speed up and cavitation down. You could also try some weight in the nose, but only until you get the rest corrected. Have fun.
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