WOT and performance - 1994 Johnson 25HP

[Jumperzee]

(Posted in the Johnson Outboard forum also)

Hello,

I have a 1994 25 HP electric start Johnson (J25TELERC) that I'm looking for the WOT rpm range for. Very reliable motor but "seems" to have lost a little top end. I'd like to try to see if I can get some more performance out of it (or back).

Boat is a 15' Sylvan Yukon, 220 pounds boat weight. Typical load is 2 guys and fishing gear (~450#), 2 batteries in stern and 6 gal fuel in mid. Planes out just fine, albeit a little slow to get on plane. Have Step-n-Trim tabs on boat. Best GPS speed was 24mph (aforementioned load), but haven't measured in a while and know it's not that fast anymore (feels and sounds a little doggy - no other way to describe). Prop is 10x13 and could stand to be replaced/repaired. Ordered an induction tach to start tuning process. Any other thoughts on what to look at appreciated.

 

[Mr. M]

Hi Jumperzee. I almost have the same situation as you and I have a post about it. My motor is a 1996 25hp and both of our motors have a Gear Ratio of 2.15
and a RPM Range of 4500-5500

 

[Sea Rider]

Check timing advance/carb synchro is spot on. If that's a 2 strokes OB an overdose of Power Tuner (Decarbon) does make wonders on 2 strokes that don't use regularly carbon guard products on fuel tanks. After that, install 2 new spark plugs. Check wot rpm with tach, probably need a small prop maximization, only tach will tell..

Happy Boating

 

[steelespike]

Guessing 12% slip 24 mph calculates to about 4800 rpm. Guessing Isn't a good idea but it does give us indication how things are going.
How does it do without the trim tabs?
They can help get out of the hole but may slow top speed.