I need a prop suggestion?

[BULLDOGG]

1) Performance issue you are trying to correct.
2) Current prop manufacturer, model, aluminum or stainless and as a minimum.
3) Current prop diameter and pitch (required).
4) Wide open throttle RPM and speed with an average load (very helpful)
5) Engine/drive make, model, year, and HP
6) Boat make model, year, length and weight


1)more speed
2)aluminum
3)13 1/4 X 17
4)4200rpm 35mph
5)Johnson 1977 85hp
6) 1968 ArrowGlass Cougar 15' 1200lbs

 

[billy4hp]

Re: I need a prop suggestion?

1) Performance issue you are trying to correct.
2) Current prop manufacturer, model, aluminum or stainless and as a minimum.
3) Current prop diameter and pitch (required).
4) Wide open throttle RPM and speed with an average load (very helpful)
5) Engine/drive make, model, year, and HP
6) Boat make model, year, length and weight


1)more speed
2)aluminum
3)13 1/4 X 17
4)4200rpm 35mph
5)Johnson 1977 85hp
6) 1968 ArrowGlass Cougar 15' 1200lbs

Not that I am a prop expert, but I think you need to make sure there isn't another problem first... The reason I believe this is I turn the same 13 1/4 X 17 prop 5400 plus rpm with my 1978 Johnson 70HP mounted on a 16' deep V hull with similar weight and make a GPS verified 35 to 37mph depending on water conditions... 5500 rpm is what Johnson suggests for max WOT on my 1978 70HP (unsure what your maximum RPM is)...

So you might have the following issues:

Engine performance problem (weak compression, carb or ignition issues)
Tachometer problem (your tach may be reading incorrectly)
Soggy boat problem (i.e. water saturated hull increasing the boats weight)...

JMHO....

 

[BULLDOGG]

Re: I need a prop suggestion?

iv have checked the compression all cylynders are reading 100psi. ive cleaned the carbs. and the spark looks good.

could be tach or water logged. previous owner. said he had a similar motor on it. and was able to do 40mph.

 

[billy4hp]

Re: I need a prop suggestion?

iv have checked the compression all cylynders are reading 100psi. ive cleaned the carbs. and the spark looks good.

could be tach or water logged. previous owner. said he had a similar motor on it. and was able to do 40mph.

One thing to keep in mind is if the PO said they had a similar motor 15 years ago and it ran 40mph they may have been using a old PITO tube speedometer which are notoriously inaccurate (usually reading to the plus side for marketing and a joy joy feel good feeling)....

A GPS sure does make everyone honest...

Good luck....

 

[hwsiii]

Re: I need a prop suggestion?

BULLDOGG, 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]

Re: I need a prop suggestion?

1) Performance issue you are trying to correct.
2) Current prop manufacturer, model, aluminum or stainless and as a minimum.
3) Current prop diameter and pitch (required).
4) Wide open throttle RPM and speed with an average load (very helpful)
5) Engine/drive make, model, year, and HP
6) Boat make model, year, length and weight


1)more speed
2)aluminum
3)13 1/4 X 17
4)4200rpm 35mph
5)Johnson 1977 85hp
6) 1968 ArrowGlass Cougar 15' 1200lbs

yeah for some reason i think you might have some other issues there.....

http://forums.iboats.com/showthread.php?t=190638

do you have another tach??? change it and see if it fixes the problem...

if tach is correct you might have to drop the pitch on the prop....