Need help getting correct prop.

bondo478

Cadet
Joined
Mar 2, 2009
Messages
19
Hello all! I have a new to me 1987 Cruisers Inc. Holiday 244. Dry weight as listed in the brochure is 3800, length is 24' without swim platform, beam is 8'. Engine is a beautifully running Mercruiser 260hp which is a new longblock and an alpha one outdrive with 1.5:1 ratio. It currently has a 15.5x16p aluminum prop on it. It takes forever to plane and WOT is 4000RPM. Specs for this engine call for 42-4600 WOT. I am also concerned due to the fact that there is very little clearance between the tip of the blades and the botton of the anti-ventilation plate. Can anyone help me decide where to start?
 

junior1113

Senior Chief Petty Officer
Joined
Jan 29, 2009
Messages
763
Re: Need help getting correct prop.

imho alluminum props suck on this type of application with the hp and the weight they flex. good starting point ss 15 pitch.
 

bondo478

Cadet
Joined
Mar 2, 2009
Messages
19
Re: Need help getting correct prop.

I'd love to go stainless but not sure I want to drop the money until I get the right prop figured out. All of the prop charts and calculators I can find seem to suggest a 14.5X17P prop in aluminum or stainless for this size, weight, and hp. Would it be a good idea to try this?
 

hwsiii

Commander
Joined
Jan 25, 2009
Messages
2,639
Re: Need help getting correct prop.

Bondo,if you are already having problems with a 16" pitch then going up in pitch will only make the problem worse.

Working over the internet and not being able to see the boat or prop the question is about makes it much harder to propose a solution to the correct prop that you need, and most people don?t know the make and model of the prop . When we get information in bits and pieces we continually have to look back and forth to try and piece the information together. The following form has all of the information that is needed to help you with your problems in finding the right prop. If you do not know all of the information that is asked for on the form please give us the most information you have available as I have a program I designed to find the right prop for any planing hull boat that needs this information. It requires time to find all this information when we have to look for it and in my defense I expect you to be willing to expend as much effort in finding the right prop as I do. We hope to be able to help you get the best prop we can for your particular uses, and this information is required to do that.
It is not as simple to pick the right prop as most people coming to this forum think it is, that is why we ask so many questions, it is for your benefit we ask all these questions. And if you have a stainless steel prop or are changing to one the blade geometry of the prop can make a lot of difference in speed and RPM. Most of my calculations are done assuming an aluminum 3 bladed prop will be used, when changing to a SS prop or changing within SS props we need to discuss what you are trying to accomplish.

Iboats Boat and Motor Info

1. Year, make and model of boat
2. Length, width and base weight of boat, look for boat decal on back of boat
3. Number of people and gallons of gas normally on boat
4. What do you use the boat for
5. Is it a Deep Vee and if so how many degrees of deadrise
6. Year, make and model of motor
7. HP and gear ratio of motor IMPORTANT
7A If you have a mercruiser and don?t know the ratio get your serial off the outdrive and go here http://www.sterndrives.com/mercruisersterndrives.html
8. Manufacturer?s recommended WOT range
9. Anti-ventilation Plate height above keel of boat if it is an outboard in inches
10. Is it a bass boat or does it have a pad bottom
11. Does it have a hydrafoil or trim tabs
12. Make, model, diameter, pitch and whether SS or aluminum prop
13. WOT RPM and speed from prop, how much gas and how many people in boat for test data
14. Are you at sea level, or a much higher elevation
15. What problems are you trying to cure or what are you looking for the boat to do that it is not doing the way you think it should or to your expectations

REMEMBER, The numbers I give you will be NO better than the information you give me

The only thing I ask of you is to come back and give me a report of WOT RPM and speed for my database.

H
 

bondo478

Cadet
Joined
Mar 2, 2009
Messages
19
Re: Need help getting correct prop.

1. 1987 Cruisers Inc. Holiday 24
2. 24', 8' beam, 3800lbs
3. Normally 3-5 people on boat, 80 gallon fuel tank-usually close to full
4. use the boat for general cruising
5. It is a deep vee, but cannot locate deadrise, and it is currently in water.
6. motor is a 1987 Mercruiser 5.7 liter.
7. 260 horsepower and 1.5:1 alpha one gearcase.
8. WOT range 4200-4600
9. Not an outboard
10. Not a bass boat.
11. Has trim tabs
12. aluminum prop, Michigan wheel 15.5X16
13. WOT RPM: 3800 speed: 28mph (from speed wheel-no GPS yet) with approximately 70 gallons fuel 3 people on board.
14. elevation 750ft
15. Currently takes 50-60 seconds to plane whether 1 person or 6 on board. Cannot reach recommended WOT. Looking for a good holeshot and to reach full RPMs.

Thanks for any help you can give me!
 

mralda

Cadet
Joined
Jul 20, 2009
Messages
13
Re: Need help getting correct prop.

Perhaps you could invest about $150 on a ProPulse adjustable pitch prop to determine correct pitch and then purchase a nice stainless steel... with the added bonus that you keep the ProPulse as a spare!
 

gostephen

Seaman
Joined
Apr 9, 2009
Messages
69
Re: Need help getting correct prop.

i would go down to a 15inch max diameter that will pull it about 1/4in fruther away from the plate.

as for pitch wait for Hwsiii to come back with some numbers
 

bondo478

Cadet
Joined
Mar 2, 2009
Messages
19
Re: Need help getting correct prop.

Yes, I am a bit concerned about the clearance with the 15.5".
 

gostephen

Seaman
Joined
Apr 9, 2009
Messages
69
Re: Need help getting correct prop.

i have the same out drive and a 15in prop is a big as i will go and thats pushing it for me
 

hwsiii

Commander
Joined
Jan 25, 2009
Messages
2,639
Re: Need help getting correct prop.

Bondo for the conditions you are in right now if you will get a 14" Pitch prop your RPM will rise to about 4,300 to 4,400 RPM and your speed will increase accordingly.


H
 
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