Glen-L.com

Thanks to our "yes, they're mandatory spray rails", we're enjoying dry sea trials in our Tahoe 23+. Now a question about speed, rpms and prop choices.

Our set-up is a PleasureCraft 351 coupled with a Velvet Drive transmission. We've started with a 13x13 3-blade prop that we had on-hand. What other options have been tried? From the forum, looks like at least one T23 is using a much steeper pitch (16+) and this raises a question about idle speed. Even with our 13x13, we're moving pretty quick at idle.

Ours will do about 10 knots / 1,000 rpm up to 3,000 rpm. Beyond 3,000, we only get a couple of extra knots while the engine is turning about 4,500 rpm, I don't think we're getting everything that's available from our set-up

Do you have the 1:1 velvet drive, or, some other gear ratio?
Can you post a photo of your transmission?

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God Bless our Troops; especially our Snipers

Corey

How much HP do you think you're putting out? That's along with KenS question on gear ratio. You've got more speed coming to you, I think.

Bill

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Mini -Tug, KH Tahoe 19 & Bartender 24 - There can be no miracle recoveries without first screwing up.
Tahoe 19 Build

KenS - As usual, best pics of projects aren't on this PC, will get you a few shots and check manufacturers plate for the specific model.

Bill - In 1979, this engine was advertised at 260hp. After test driving it when it was in the original hull, I'd say most of the power is still there....

Pictures coming tomorrow.

Some of the other guys turning 16+ pitch are running Fuel-Injected MPI engines and/or Big Blocks, or down angle tranny with 1.23 gears.
you should be within the ballpark with 260hp, 4500rpm, 1:1 gear, and 13x13.

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God Bless our Troops; especially our Snipers

Pictures at last, sorry for the delay...interested in your thoughts....

That is a 1:1 gear.
It is not a reduction gear.
That is correct for a Tahoe. with your 13x13 you should be within the ballpark as far as speed and rpm.
Perhaps the clutches are slipping?
Can you attain WOT (wide open throttle)? and determine engine RPM at WOT?

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God Bless our Troops; especially our Snipers

I think Ken is on to it. Everything sound right. Something must be slipping.

Bill

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Mini -Tug, KH Tahoe 19 & Bartender 24 - There can be no miracle recoveries without first screwing up.
Tahoe 19 Build

Look at that prop,,,,how much cupping is on it,,,,, (none perhaps?)

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God Bless our Troops; especially our Snipers

Thanks for the feedback!

Just dropped the boat off for upholstery so won't be able to have a look at the prop cupping for a few weeks. In terms of "slipping clutches", will do some research on the Velvet Drive - aside from fluid levels and the cable adjustment, I didn't think there was anything to adjust so perhaps its time for a rebuild (the transmission, like the engine is '79 vintage).

Do you have one of those photo tachs? Output RPM should be the same as engine RPM.

Looking at your original post, you mentioned 30kts. 30kts is none too bad. Different from 30mph.
I think we need more & better numbers before you outlay $$ for a tranny rebuild.

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God Bless our Troops; especially our Snipers

You did put the key in when you fitted the prop?? You are correct, no adjustments on the Velvet Drive. Hopefully it is something simpler than the tranny like missing key or something. If you are doing 10 knots at 1000 rpm and still only 10 at 3000 the torque is certainly not getting to the prop. Check flange coupling and propeller key and hope one or other is not right.
Best of luck, and let us know what you find.
Glenn.

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By the time I have built a boat, I'll be ready to build a boat....

Did some reading on Velvet Drive fluid levels last night and am hopeful that's the culprit - am pretty sure that the last fluid level check I did was done cold and wouldn't have accounted for any fluid that will move in to the cooler. Provided the local harbour isn't frozen when the boat returns, will check this first. Also realized that I rebuilt the TeleFlex shifter assembly and need to check that I used the correct holes for the shifter-end of the cable: frustrating to think of these things while the boat is laid up!

Trackhappy: am 100% sure that the drivetrain is tight and has all her parts. We're getting about 10knots for every 1000 rpm - at 3000 rpm, we're getting just over 30knots (34.5mph).

What is RPM at wide open throttle?
you need to know this number.

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God Bless our Troops; especially our Snipers

Working from memory here Ken, but I recall around 4500.