The right prop for my 25 johnson?

[ctbs]

Hello,<br />I took my "new to me" 1976 J 25hp out for her maiden voyage and was pleased over all. This was a very clean, low use outboard that I couldn't pass up for $450.00. Really pushes my 14' aluminum semi V along compared to the 15hp Force I had on her! I did notice however that it took about seven seconds for the rpms to peak after I gave her full throttle. Once she peaked out, she ran flawlessly. I'm wondering if my Michigan three blade prop stamped "510" is not the right match for the engine. The standard prop should be a 9 x 10 three blade (or close to it). I checked out the MP web site and couldn't find a match for "510" - so I'm not sure of the pitch. This isn't a 5 degree prop is it? Perhaps unrelated (?) the engine will conk out when idling in the lowest setting. Might this be a lean/rich adjustment?<br />Thanks for considering helping out,<br />Chris

 

[Hooty]

Re: The right prop for my 25 johnson?

I can't help with the Michigan 510 but I offer a coupla ideas. First, if you want to prop it out right, you'll need a tachometer. You can get one from TinyTach for thirty or forty dollars. I'll post their addy below. Just call 'um up and tell 'um what engine you've got and how long a wire you'll need. If you don't want to do that, find a good prop shop and take your boat and motor to 'um and ask their advise. They'll probably know what pitch the "510" wheel is to.<br /><br /> TinyTach <br /><br />c/6<br />Hooty

 

[ctbs]

Re: The right prop for my 25 johnson?

To update,<br />I stopped by my local prop repair shop. They s// the said "510" was stamped on the prop after market - probably by some repair guy previous. Anyway, the "JP19" identified it as an older Michigan prop, 9 x 9 which would be considered a "heavy" prop for this year and make motor. It sis in very nice condition. Any other ideas about my delayed RPM situation knowing all this?<br />Kind regards,<br />Chris

 

[E120B]

Re: The right prop for my 25 johnson?

Howdy..<br /> I Have a 85 Rude 25 On My Deep V 14' alum boat, i have a 10x13 prop on it and my rpms are great, Talk to you local prop guy and see if he will let you try out a prop or two and see if the rpms are right

 

[Jack Shellac]

Re: The right prop for my 25 johnson?

According to the manual for this motor, the standard prop supplied is a 3 blade, 9 x 10. The only optional prop offered was a 3 blade, 9 x 9. I would think that, with your rig, a 10" would be better. But, as Hooty says, the only way to be sure you have the right one is with a tachometer.