need a prop recommendation; 94' Maxum new motor

[benblank]

I have a 1994 Maxum 2000CR (20'), it currently has a 06' Mercruiser 4.3 EFI with an Alpha 1 drive. As it sits the boat has a Aluminum 14" 21 degree pitch prop.

Typical use for the boat is to occasionally pull some tubes or skiers/wakeboard but most of the time is spent cruising to the sandbars which can be a 5 mile ride. Typically we have 4-8 people with us at any given time and while cruising at 5k RPM's see speeds of 40-44 depending on water conditions. The problem I have is when cruising the buzzer for the RPM's (5k max) seems to come on well before I reach WOT feels like 75-80% throttle. I am somewhat new to boating but it feels like the prop may be slipping at these higher speeds? I have been thinking of getting a aluminum 23degree prop and seeing if this helps when cruising at these higher speeds but would appreciated the opinion of some more experienced boaters.

 

[rndn]

Re: need a prop recommendation; 94' Maxum new motor

The prop calculater comes up with 4800 rpm's for the maximum and suggests a 23 inch prop. All else being equal the 2 inches of extra prop should decrease the maximum rpm's by 400. There are many differences in prop manufacturers so it would be possible to lower the rpm's just by switching brands.
Also know that by going up in pitch you will increase your time to plane, by how much all depends on the boat. If that's a concern with tubing and skiing you may want to think about a 4 blade unless you already have trim tabs.
http://www.turningpointpropellers.com/
The link is for the prop calculator, but if you make a purchase please buy from iboats.com, the company that provides this forum for us.

 

[benblank]

Re: need a prop recommendation; 94' Maxum new motor

The prop calculater comes up with 4800 rpm's for the maximum and suggests a 23 inch prop. All else being equal the 2 inches of extra prop should decrease the maximum rpm's by 400. There are many differences in prop manufacturers so it would be possible to lower the rpm's just by switching brands.
Also know that by going up in pitch you will increase your time to plane, by how much all depends on the boat. If that's a concern with tubing and skiing you may want to think about a 4 blade unless you already have trim tabs.
http://www.turningpointpropellers.com/
The link is for the prop calculator, but if you make a purchase please buy from iboats.com, the company that provides this forum for us.

Thanks for the the input, I was thinking about going with the TP Hustler 23 inch. I was also thinkging about the Solas Amita 23" 4 blade, In the limited bit of information I have read it seems 4 blade props improve the performance aspect in everything but leave a couple 1-3 mph on the table on the top end?

 

[benblank]

Re: need a prop recommendation; 94' Maxum new motor

Or would a 4 blade 23inch prop possible be to much?

 

[hwsiii]

Re: need a prop recommendation; 94' Maxum new motor

Ben, you would be much better off for your uses if you bought the solas amita 4 blade and you would want to stay with a 21" pitch, as it will bring your RPM down about 300 or 400 RPM anyway.


H

 

[benblank]

Re: need a prop recommendation; 94' Maxum new motor

Ben, you would be much better off for your uses if you bought the solas amita 4 blade and you would want to stay with a 21" pitch, as it will bring your RPM down about 300 or 400 RPM anyway.


H

If I am to go this route, should I see some gain on the top end? Because I typically do more cruising I was hoping to pickup a couple extra MPH...

 

[hwsiii]

Re: need a prop recommendation; 94' Maxum new motor

If you will take the boat out again and get me some speeds and RPM numbers from 3,000 RPM up to WOT at 500 RPM intervals I can figure out how much prop slip you are having when it is loaded and that will give us a good indication of what a 4 blade prop would do for you. Also let me know about how much weight in people you had on the boat.


H

 

[benblank]

Re: need a prop recommendation; 94' Maxum new motor

If you will take the boat out again and get me some speeds and RPM numbers from 3,000 RPM up to WOT at 500 RPM intervals I can figure out how much prop slip you are having when it is loaded and that will give us a good indication of what a 4 blade prop would do for you. Also let me know about how much weight in people you had on the boat.


H

Alright hwsii, I appreciate that very much. I will try and get out this weekend and get some good data for you. I also have GPS on my phone so I can get some accurate MPH also.

 

[hwsiii]

Re: need a prop recommendation; 94' Maxum new motor

That wiil be great.


H

 

[benblank]

Re: need a prop recommendation; 94' Maxum new motor

hey so I was able to get on the lake this weekend...

Had 6 people aprox 1050lbs
full take of gas aprox 36 gallons

3000 - 17
3500 - 27
4000 - 34
4500 - 38
5000 - 42

1994 Maxum 2000sr w/ 2005 Mercury 4.3l EFI

current prop is a 3 blade 21 degree aluminum

 

[hwsiii]

Re: need a prop recommendation; 94' Maxum new motor

Ben, evidently I don't have the right basis on your motor. I show recommended RPM 4,400 to 4,800 and a !.82:1 gear ratio, can you verify that.


H

 

[benblank]

Re: need a prop recommendation; 94' Maxum new motor

How can I verify the gear ratio? Its an Alpha 1 drive...

 

[hwsiii]

Re: need a prop recommendation; 94' Maxum new motor

Alpha 1 have many gear ratings is it a 1994 or a 2006 drive unit



H

 

[benblank]

Re: need a prop recommendation; 94' Maxum new motor

Pretty sure it is the 94 drive, how can I confirm the year and gear ratio?

 

[hwsiii]

Re: need a prop recommendation; 94' Maxum new motor

Put a piece of tape across the prop and the drive then cut the tape between them and pull the plugs and turn the motor until the tape lines back up and count the revolutions you had to turn the motor.


H

 

[junior1113]

Re: need a prop recommendation; 94' Maxum new motor

post all #'s you can find on out drive and on motor

 

[hwsiii]

Re: need a prop recommendation; 94' Maxum new motor

And the engine can be either a 190 HP or 220 HP, I need to know which..

 

[hwsiii]

Re: need a prop recommendation; 94' Maxum new motor

Ben the following is the prop slip for your prop if it is a 1.82:1 gera ratio as I show it to be. And this is very high, but you did have a lot of people in the boat. I do recommend a 4 blade prop to bring your prop slip down. When you were at 5,000 RPM did you have much throttle left.


Prop Slip

H

 

[benblank]

Re: need a prop recommendation; 94' Maxum new motor

Ben the following is the prop slip for your prop if it is a 1.82:1 gera ratio as I show it to be. And this is very high, but you did have a lot of people in the boat. I do recommend a 4 blade prop to bring your prop slip down. When you were at 5,000 RPM did you have much throttle left.


Prop Slip

H

At 5000 RPMs I still have a decent amount of throttle left, enough where I can still mash it. The results I posted are pretty close to what I see when the boat isn't as loaded down. For example when I have say 3 people in it I may hit 44 if the water is like glass. So you recommend a 4 blade, should I stay with the 21degree or go 23degree 4 blade?

 

[hwsiii]

Re: need a prop recommendation; 94' Maxum new motor

Ben, I recommend a 23" Solas 4 blade prop for your uses, you apparently still have throttle left at 5,000 RPM even with 6 people on the boat. I made a guess that you can potentially get up to 5,200 RPM even with that load.

Prop Change

With the new prop you will find that your prop slip will go down but you may lose some of your hole shot and acceleration because of the increase in pitch, but you may gain a little speed as well.


H