Johnson 25 Propping question

[Playing Hookey]

Hi all,
I apologize for posting this in the wrong section.
I'm a lowly newb.

I have a new (to me) 1987 Johnson 25 long shaft. I purchased the motor to hang on my 1988 Grumman 14 foot modified V hull. I do not have access to a tachometer for testing RPM which I KNOW is the best method for selecting the best prop.

The motor has a prop on it. I measured 10 inches for the diameter. I do not know the pitch as the stamped numbers have been painted over. The previous application of this motor was on a 16 foot MFG hull which I understand was significantly heavier than my Grumman.

Can anyone suggest a diameter and pitch that would work well as a good overall performance prop? The hull weighs about 225lbs, the motor, 110lbs. I figure the typical load of persons and gear will be between 500 - 700 lbs.

Anyone care to predict my top end speed when properly propped/trimmed?

Thanks for helping out. I just need to paint the new transom this weekend and she'll splash next week.

Hookey

 

[SnapperHunter28]

Re: Johnson 25 Propping question

I'd say with the right prop, and trim, at least 30. I had a similiar setup, and hit 32 on gps...so...I'd say close to 30.

 

[Kamdyn]

Re: Johnson 25 Propping question

I would go with a 10x11 pitch prop, I am currently running a 10x13 pitch but I want more hole shot so I will be switching over soon. I had a few 25's and I noticed that they all were strapped with a 10x13, I dont know if this is a standard pitch for this size of motor but the 10x11 is ideal to plane real quick.

 

[anzomcik]

Re: Johnson 25 Propping question

I own a mariner 25, i consider my 14 foot boa tto be on the heavy side. Mainly because i have alot of crap in it. But so far my best prop has been a 13 pitch, the best speed and i only hit it once was 28mph, normaly 23-24mph is the normal.

Right now i am experinmenting with different pitches and makes of props and finding out that 24mph average is about as good as i am going to get. The wild thing is i plane faster with my 13 than i did with the 11, my 11 had alot of venting issues causeing poor mid range preformance.

Both 13 pitch and 11 pitch props were in the rec. WOT range. IMO if your boat isnt loaded super heavy go for the 13 pitch. Search the prop section of the forum for my review of the solas amita 3 and hustler rascal. I have since tryed the amita 4 11 pitch. I did not post the results yet.