what the best prop for my boat ???

[Grew 194]

ok I know this might be a dumb question but I just want to make sure I have the right prop on my boat so that I don,t wreck the motor or any other parts ??? the boat is a Grew 194 with merc 165 inline 6 cylinder with pre alpha leg now I have a 19 and a 21 prop this is the boat

 

[Silvertip]

Re: what the best prop for my boat ???

Didn't read the READ THIS FIRST sticky huh????

 

[steelespike]

Re: what the best prop for my boat ???

We can help you better if you answer the stickys at the top of the prop forum.

 

[Grew 194]

Re: what the best prop for my boat ???

We can help you better if you answer the stickys at the top of the prop forum.

I read the sticky !!!! didnt help me much as I don,t know the weight and I don,t know the gear ratio that is why I posted what boat it is and what it has for a motor and the size of the boat . But if all I am going to get from you people is READ the Sticky then I will get my answer some where else .

 

[Silvertip]

Re: what the best prop for my boat ???

You also didn't tell us what the current wide open throttle rpm is with what you consider an average load. Thats the key data. The optimum prop Is one that allows the engine to rev at or very near the top of the engine manufacturers recommended WOT rpm band. And a change of prop is not a fix for a poorly running engine or a boat with a dirty or water soaked hull.

 

[steelespike]

Re: what the best prop for my boat ???

I read the sticky !!!! didnt help me much as I don,t know the weight and I don,t know the gear ratio that is why I posted what boat it is and what it has for a motor and the size of the boat . But if all I am going to get from you people is READ the Sticky then I will get my answer some where else .

You are on the best forum by far for the number posting and the informed contributions.
While there are various formulas for determine a prop range none can rate your particular boat and its particulars from its age and condition and your requirements.
If you give us the year of your boat we might be able to determine the ratio and the weight.
Your ratio may appear on the leg. Sometimes it is necessary to manually determine the gear ratio.
There is no way to determine the exact prop for your particular boat without at least your present prop size,wot rpm and gps speed
in combination with the gear ratio but without it we can't evaluate your setup.
Did you note the number of posts by myself and Silvertip and any number of other contributors?

 

[steelespike]

Re: what the best prop for my boat ???

I've spent about 30 minutes researching your boat.
Tried to find your boat.Appearently they went out of business circa 2011.
Don't know the year of your boat but it appears the 194 weighs about 2600 lbs.
The 165 in line has a 3900 to 4300 rpm range.gear ratio is 1.65.
We would have been glad to look up specs. on the net but if you were lucky enough to have the info first hand
it helps to eliminate errors.
Now if you can get us the prop size and wot rpm and gps speed we can probably tell you if your present prop works or suggest a change if necessary.

 

[Grew 194]

Re: what the best prop for my boat ???

Ok here is what I have ... I did find the same info as Steelespike Thank you for posting it the boat is a 74 and does have the inline 6 cylinder that is a 250 gm motor with the 1.65 ratio leg . My tach is not working at this time as I have to get a new one but the speedo with the 19 prop makes the boat go about 32 mph and the 21 prop made the boat go about 38 mph now the reason I am asking is when taking off it seems that the boat takes a bit of time to plane out. at first I thought it was because I throttle up slowly but it made no difference if I did it slow or quickly , I even filled the fuel tank up front to see if that would make a change putting more weight to the bow . this boat is only in the water maybe 3- 4 times in the summer.

 

[steelespike]

Re: what the best prop for my boat ???

The calculator indicates the motor is not reaching max rpm.
Guessing 12% slip The rpm with the 19" is 3350,the 21 produces 3600 rpm Its unusual for the higher pitch to produce more rpm.
Perhaps the 21 is stainless or is more sophisticated. If its stainless it will be magnetic.
Are they 3 blade props?See if you can find the diameter,near the base of the blades or under the prop nut.
It would be better if you can get a test with a gps.
Also perhaps you could borrow or rent a shop tach to confirm the rpm.Calculating rpm is a gamble.
Do you trim down for hole shot? Does the boat respond to up trim?
It's my feeling the props should produce more rpm. and speed the 21 for speed and cruising the 19 for more weight
and perhaps water sports.I could be over estimating but they are good starting points.
Before any changes you should be sure the motor is in excellent tune.Good compression.Be sure the timing is set right and
advancing as it should.Be sure the throttle is opening all the away.

 

[Silvertip]

Re: what the best prop for my boat ???

Until you have functioning tach.do not spend any money on props. The tach will tell you if the drive is over propped, under propped, or spot on. And before buying a new tach, make sure the one you have is actually bad.

 

[Grew 194]

Re: what the best prop for my boat ???

ok fellas thanks for the great info I will see if I can find the diameter of the props and they are both aluminum props 3 blade

 

[MarcPierre]

Re: what the best prop for my boat ???

Was there any resolution? If you need to find props there is a good site I go to. boat propellers