1984 johnson 25hp prop question.

[Eyeballsdeep]

I have an 84 25hp johnson and I want a little more out of it. It's on a fairly light fibreglass 15' chriscraft runabout with the top hull removed and just a couple wood bench seats I made. The prop on it now is an 11x9.25 would it be possible to tweak it myself? Are there any threads on this. I was thinking of making my own pitch block. I Work at a foundry and can pour a rough shap and grinde it to a desired shape. I mean I'm not trying to turn it into a race boat maybe 13 or 15 pitch. Seems like it runs a little high in rpm's I have no idea what rpm it's at.

 

[steelespike]

Re: 1984 johnson 25hp prop question.

You really can't tell without a tach and the lightly loaded wot rpm and gps speed.For the best performance and the health of you motor you shouldn't make any prop changes without these things.Some cells have a gps app.Is the prop a thru hub exhaust or non thru hub exhaust?
An induction tach like a Tinytach, easy to install and will work on almost any motor sea or land.
There are some hard wire tachs that work well too.
If you describe your present performance, estimate weight, hole shot, lightly loaded gps speed,typical load gps speed ,
we may be able to tell if your setup needs help or will respond to treatment.
Some things to check; be sure the throttle opens all the way,the anti vent plate (just above the prop) should be about even with the bottom of the transom.The less motor in the water the better the results.Bottom clean and smooth no peeling paint.