Prop Pitch

jrwdelton

Recruit
Joined
Jun 24, 2008
Messages
1
I have a 25 foot, 8.5 ft beam, 4500lb dry boat. it has a 5.7ltr 350, and should run about 4500 rpm. It doesnt want to get up on plane. i've got a 14 1/2 x 15 prop on it now. Any suggestions as to what would work better to get it up on plane and stay up. I've looked at all the charts, but I want some info from someone that has a similar sized boat. it calls for a 14 pitch for our mph, which should be 22 cruising to 30mph top end. but I woould like some info before I buy one. Would i be better getting a 19 pitch??? any info will help thanks
 

hwsiii

Commander
Joined
Jan 25, 2009
Messages
2,639
Re: Prop Pitch

Delton, we will try to help you as much as we can, but there is certain information that is needed in order to help you. 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, and most other people who are trying to help you will need the same 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 exact prop you need 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.

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
8. Manufacturer?s recommended WOT range
9. Anti-ventilation Plate height above keel of boat if it is an outboard in inches
10. Does it have a hydrafoil or trim tabs
11. Make, model, diameter, pitch and whether SS or aluminum prop
11. WOT RPM and speed from prop, how much gas and how many people in boat for test data
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
 

steelespike

Supreme Mariner
Joined
Apr 26, 2002
Messages
19,069
Re: Prop Pitch

It certainly should plane with a 15.It might need less pitch but should plane.
I suspect you have a motor issue.Be sure its running on all cylinders.Throttle is opening all the way.Motor is in perfect tunegood compression.Prop is in good shape.
Going to a 19 will make things worse like trying to start out in 2nd gear in your car.
 
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