prop change

[roadstarmoney]

i have a 2004 tahoe 19 ft with a 4.3 with alpha one and want to change prop for more top speed. WOT is 5000 rpms at 49 mph. i have a 21 pitch 3 blade prop and am thinking of replacing it with a 23 pitch 4 blade solas amita prop. does this sound like the right pitch to buy and is the solas amita a good prop?

 

[bnicov]

Re: prop change

What is the operating RPM range of your engine/drive combo?? 5000rpm sounds kind of high. You can go to a 23 pitch prop and that will probably bring your RPMs down a bit and MAYBE give you some more speed. To break 50, you'll probably have to go to a stainless steel prop and they aren't cheap. I'd be more concerned with how quick the boat gets up on plane and how it cruises. If you run at top speed all them time you will have 2 new best friends, the kid at the gas dock and the local engine rebuilder. I've got an 18.5ft'r and don't care so much about top speed, I know I can go 45-50mph but I'm more worried about getting on plane quick and cruising between 24-30mph, go faster and it starts to suck fuel too fast. Solas makes a good prop, I wouldn't worry about them.

 

[steelespike]

Re: prop change

2 different 4.3 190 and 220 From the calculator numbers I'm guessing 190.If your gear ratio is 1.81
your slip is just a tad high 10% would be high normal but 6% would get a touch more speed about 51.
If you got the a 4 blade in a 21 your rpm should be close to4800 and 50.The 4 blade should improve hole shot
and handling at speed and at the dock.A 3 blade 23 would net about 4600 at 10% slip a whisper below 50 at 6%
51 plus. Any speed increase at what amounts to 50 mph allready would normally be small.
A speed increase going to a 4 blade is unusual but with the 10% slip if the 4 blade gives us 6% slip that would add a touch of speed.

 

[roadstarmoney]

Re: prop change

Ordered the prop from iboats on friday and got it on tuesday (yesterday) installed it and went to the lake. WOT changed from 49mph at 5000 rpms to 55 mph at 4500 rpms. Will cruise now at 46 mph at 3800 rpms. Gets up on the step quicker than with the 3 blade 21 pitch. i installed the solas amita 23 pitch 4blade prop. mine is the190 hp 4.3 and i don't know what the gear ratio is but i am tickled at the results. Thanks for all the help from everyone.

 

[steelespike]

Re: prop change

I think there has been a vast improvement in slip numbers and of course the pitch increase helps the speed.
However the nmbers aren't quite right.You can't go 55 at 4500 my guess is the tach may be low or the speed slightly high.
54 mph produces a rediculess 2 tenths of a percent slip.Not possible.
No matter;you had an excellent increase in speed and are probably now well within solid slip numbers.
Does the 4 blade still retain a strong hole shot?

 

[Monterey10]

Re: prop change

I'm hearing many good things about the 4 bladed props. The only thing that could be better is the DuoProp.

 

[roadstarmoney]

Re: prop change

Hole shot is great, will take the gps next trip to lake, and another tach. Tell me more about the DuoProp. I have seen some of them on larger boats. i guess that is what i saw yesterday. one in front of the other is what it looks like. Do they work really good and what about cost. I am really happy with the one i have though.

 

[steelespike]

Re: prop change

I don't know too much about the details of a Duo Prop.
It is a system not just two props. There is a special gearcase that is setup for counter rotating matched props.
Not something that you would normally add to an existing boat Unless you stumbled on a whole system.
You might ask about the duo prop in the I/O section.

 

[bnicov]

Re: prop change

You'd be looking at a BravoII drive and around $10k to switch over. Not worth it. Duo Prop drives work really well in heavy boats but as I mentioned, they are expensive and you wouldn't benefit too much over your current setup. That your holeshot is great and you are cruising really fast at lower rpms, I'd say you picked a WINNER!!