Glastron Carlson CV-23 Prop Question

[fireman24mn]

I just finished restoring a 1977 CV-23 I/O I have completely replaced all the wood in the boat. I then installed a Alpha1 Gen 2 drive. And a new 383 small block about 360 HP and 410 Torque. I have raised the drive 2 inches. The hull is blueprinted, sharpened strakes, knife edged the transom, and removed all the hook in the hull.Through out the rebuild I have removed about 500 lbs of weight (from Stock) using different materials and different engine parts. I have tried a 23p 3 blade forget the brand. Was about 62mph and over 5500rpm before I would pull back. I currently have a 25p 4 blade Powertech TRO on there. I am only getting about 65mph and I am over revving the boat to about 5600rpm. I would like to be at 5,000 RPM Thoughts suggestions?

 

[Maclin]

Taller drive ratio would help, but you did not mention the drive ratio. Alpha Gen2's go only to 1.50 I think lowest number, maybe Gen1 at 1.47?. A Bravo 1 gets into the 1.32 I think. Maybe a TRS racing drive?!?!???

 

[fireman24mn]

It is a stock 1.50 ratio. Just looking for prop recommendations with the current setup.

 

[QBhoy]

Hi there...firstly what a beautiful boat...so jealous.
Secondly, I'm a bit confused around your figures...they surely aren't normal products when referring to the prop pitches you mention ? There is a Alpha one gen2 with 1.47 ratio. I have one on a 2003 model. As impressive the horse power you have may be, I'm not sure the engine and the weight of that boat would see such RPMs if it was a 1.47 and those props. It's clear you aren't new to this, but I'll ask anyway....is the tach correct ? With the figures given...to drop to 5000 rpm you would need a crazy and almost unheard of pitch in most similar applications.

 

[jimmbo]

At what rpms are the Peak HP and torque occurring?

 

[Maclin]

How close to the surface is the prop running?

 

[fireman24mn]

The drive from a 1996 celebrity that had a 350 in it. As far as I know tach is correct. It is all me ignition and new gauges.

I'm thinking I need a large diamiater prop something in the 15-16 in diameter. I think I am current Amy getting a lot of prop slip. Talked to a prop shop they are thinking a 25p 4 blade power tech OFS. I just don't want to spend 450 for it and not to be what I need.

 

[QBhoy]

From what I've read, there is nothing like a big Rev 4 to bring the rpms down in comparison to a same pitch normal guise 3 blade performance prop of smaller diameter.
Also famous for going into gear with a great clunk on the alpha 1 though !

 

[ahicks]

That does sound like a neat boat with the work you've done on it. Though I have a pretty good handle on props, for a boat like this, I'd be looking for somebody that knows way more about higher end performance applications. This is not an average runabout you're playing with. After what you've been through to get the hull right, you don't want to leave a serious chunk of available performance laying on the table. Finish the project correctly and seek out a pro (hopefully you can find one locally?) - even if it cost a few bucks more.

 

[Scott Danforth]

I just finished restoring a 1977 CV-23 I/O I have completely replaced all the wood in the boat. I then installed a Alpha1 Gen 2 drive. And a new 383 small block about 360 HP and 410 Torque. I have raised the drive 2 inches. The hull is blueprinted, sharpened strakes, knife edged the transom, and removed all the hook in the hull.Through out the rebuild I have removed about 500 lbs of weight (from Stock) using different materials and different engine parts. I have tried a 23p 3 blade forget the brand. Was about 62mph and over 5500rpm before I would pull back. I currently have a 25p 4 blade Powertech TRO on there. I am only getting about 65mph and I am over revving the boat to about 5600rpm. I would like to be at 5,000 RPM Thoughts suggestions?

you modified the hull to go fast

you raised the X dimension 2" to go fast

why are you limiting your build to 5000 RPM? As jimmbo asked, where does your motor make power?

if you built the motor right and balanced the rotating assembly, your limited to when the cam and intake start to run out of breath. with hyper-e's PM rods and a balanced cast crank you could run all day at 6000 if you want. Forged internals with a balanced rotating assembly and you can run it all day well above 6500. (make sure you use synthetic oil in the drive)

Stock motors are limited to 5000 RPM because of the crappy assembly line balance (or lack of balance), mediocre cam and cast pistons/rods/crank.

 

[ahicks]

I'm darn sure no pro engine builder, but I did learn a few lessons with a big block Sanger a few years back. I ended up with a very expensive pro built engine that would spin main bearings inside of 1/2 hour, no matter how carefully it was broken in or what kind of bearings were used. I was told there were some harmonics involved around 5500, but if those were avoided, the engine was good for 6000-6500 (yes, big block).

Eventually I was sent to a small shop where some serious drag racers were hanging out for a quick talk with them. It turned out the baffled Corvette oil pan I was running was being pumped dry, with the oil unable to drain back from the rocker areas and lifter galley quickly enough. Kieth Black (think Hemi builder) suggested I go with a specially built 18qt oil pan a friend of his was building. It was nearly as wide as it was long, and of course fully baffled. That was the answer! No more blown engines. It ran over 10 years after that until I sold it.

My point is, if you're going to move your red line much over 5000-5500, you had better have some serious oil pan capacity, or even the finest engine components will fail miserably....

 

[fireman24mn]

From pretty much everything I had read and talked to people about the Alpha drives don't like over 5,000 RPM. Have you guys had luck with them over 5,000 I would never cruise at WOT for more than a minute or 2 however I don't want to keep replacing drives either.

 

[Maclin]

My brother just opened up a race 5.9 MoPar V8 and sent pictures, it was a cast iron block but the lifter valleys and other surfaces had been shot peened or simitar to totally shiny and smooth. I said it was probably to get the oil to slide off just that much easier and hit the pan just a little sooner.

Anyways, I was just wondering if the style of prop needed to mimic more of a surface runner type maybe.

 

[porscheguy]

With the raised x-dimension, and if you enter your data in a prop slip calculator, you're at 26% slip. Your prop is obviously surfacing. Your best bet is to talk to a prop shop with a background in surfacing props. And get out your checkbook.

 

[Scott Danforth]

From pretty much everything I had read and talked to people about the Alpha drives don't like over 5,000 RPM. Have you guys had luck with them over 5,000 I would never cruise at WOT for more than a minute or 2 however I don't want to keep replacing drives either.

friends of mine had twin alphas on stand-off boxes behind build 383's in a wiener boat. rev limiter was 5600 RPM. he was running amsoil. beat the boat for years until he went bigger/faster/more expensive to gas up wiener boat

 

[QBhoy]

With regards to the Alpha's and being worried about high rpms...this might not be the main concern. I'd imagine the concern may be more focused around the shear torque you are putting through a pretty modest and simple drive. I'd imagine that if you are taking it easy under acceleration and not allowing the powerful engine to effectively tear the drive to bits...you should be ok.
My boat is running a comparably modest 300hp (estimated) through an alpha 1....which is apparently acceptable any day of the week, but mechanical sympathy tells me that it isn't good for it to let loose on WOT from a standstill....which I've never done.

 

[fireman24mn]

I finally ended up finding a couple bigger props locally to try. I have a 25P Hydromotive Intimidator quad 4 and a Mercury Rev 4 both 25P

 

[QBhoy]

Let me know how you get on...I'd love to hear.

 

[fireman24mn]

So I tried the 2 props this weekend. The 25P Rev 4 got me to 67.3 however my rpm stayed about the same at 5500. I then tried the Hydromotive 25P and again 5500 rpm with a top speed of 68.4. I am thinking I will need a 27P to get my rpm down and or a prop with a lot of cupping to help so I don't have as much slip.

Any other thoughts or suggestions?

 

[ahicks]

I love cupped props....