needing help with prop pitch

allwazag8r

Recruit
Joined
Jul 12, 2009
Messages
4
I have a 17.6 Sea chaser RG with a 70 hsp yamaha. I have ballistic stainless prop 13 5/8 x 17 that gets a terrible hole shot n fuel mileage. I had the factory prop 13 1/4 x17 that would get out of the hole but will only turn about 4800 . I am looking for any answers to fix my problem. I am wanting to buy a new prop but i could not get any answers at my local boat dealers.... thanks n advance
 

WAVENBYE2

Lieutenant Commander
Joined
Apr 28, 2007
Messages
1,636
Re: needing help with prop pitch

I use a 21p prop, and get better fuel milage, it lowers my rpms but I don't pull any skiiers or tubers, so its a little slower out of the hole but I get better milage because my wife and do alot of cruising at longer distances so the prop is perfect for my use. it all depends on how you use you boat.
 

hwsiii

Commander
Joined
Jan 25, 2009
Messages
2,639
Re: needing help with prop pitch

All, welcome to Iboats prop forum and we will try to help you as much as we can, but there is certain information that is needed in order to help you. Working over the internet and not being able to see the boat or prop the question is about, and most people don?t know the make and model of the prop, makes it much harder to propose a solution to the correct prop that you need. When we get information in bits and pieces we are continually having 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. ALL 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. 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
 

countvlad

Chief Petty Officer
Joined
Jun 29, 2009
Messages
439
Re: needing help with prop pitch

I have a 17.6 Sea chaser RG with a 70 hsp yamaha. I have ballistic stainless prop 13 5/8 x 17 that gets a terrible hole shot n fuel mileage. I had the factory prop 13 1/4 x17 that would get out of the hole but will only turn about 4800 . I am looking for any answers to fix my problem. I am wanting to buy a new prop but i could not get any answers at my local boat dealers.... thanks n advance

i would not change the prop yet.... for how long have you had this boat??? when was last time you had a decarb?

first thing find out what is the recomended WOT range for the motor....
 

allwazag8r

Recruit
Joined
Jul 12, 2009
Messages
4
Re: needing help with prop pitch

Hello , sorry about the info but here is what i know. the wot is about 5100 rpm with a top speed of 33( solo) with my wife n 2 kids (13 N 7) i can run wot at about 4800-5000 with a speed of 28.. i hope this info is helpful n i can get some good feedback.... thanks
 

countvlad

Chief Petty Officer
Joined
Jun 29, 2009
Messages
439
Re: needing help with prop pitch

Hello , sorry about the info but here is what i know. the wot is about 5100 rpm with a top speed of 33( solo) with my wife n 2 kids (13 N 7) i can run wot at about 4800-5000 with a speed of 28.. i hope this info is helpful n i can get some good feedback.... thanks

ok well you still havent answered my question, what is the manufacturers recomended WOT range for that motor? very important .... find buy an owners manual.... go on the manufacturers website find a manual...

usually for an outboard the range is 5000-6000... if thats the case you might need another prop....

there are a lot of people that can help you but without more info its very hard...
 
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