Top speed w/ Johnson 15

[jmendoza]

There was post about top speed. I wanted to add that with a 145 pound 12 foot long welded Western Aluminum boat, a full tank of gas, 50 pounds of gear, and my 190 pound *** on the seat, I can go about 18 mph. I'm at 6800 feet on Big Bear Lake, and have a 9-1/4 x 8 inch prop: smaller for altitude.
At sea level in salt water(more bouyancy) with the stock prop and same load it will do about 23 mph.

If you skim about .015" inches off the head, and replaced the reeds with ones made from .018" G-10 epoxy glass, and file and polish the lower unit and skeg, and get a racing prop, and replace the stock carb with a Tillotson diaphragm type of bigger bore, and lighten the flywheel, you can get the boat going 35+ but that's the class A racing set-up.

 

[bktheking]

Re: Top speed w/ Johnson 15

It was my post, thanks for replying J. I went and measured everything up, the motor was 1 3/4 inches (CAV Plate) lower than the keel. I'm going to get a custom plate made to raise it up. Thinking it might make a difference.

 

[jmendoza]

Re: Top speed w/ Johnson 15

That might do some good, although I have only found prop ride height makes a big difference on my surface drive hydros. That said however, I have no experiencing adjusting prop depth on samll fishing boats as this is normally fixed by the transom height. You did mention something about the throttle linkage cam being updated: Did you check to see the magneto plate is at full advance at full throttle? Mine was off and I got a little more speed out of it by adjusting it.

Still love the photo of the zip tie under the reeds, classic! On all 2-strokes, I listen for reed honking, or wheezing; a simple sound check that verifies the reeds are working and you have crankcase compression.

 

[Chinewalker]

Re: Top speed w/ Johnson 15

Only 35+? A buddy of mine has his ASR running well over 50!

 

[bktheking]

Re: Top speed w/ Johnson 15

You did mention something about the throttle linkage cam being updated: Did you check to see the magneto plate is at full advance at full throttle? Mine was off and I got a little more speed out of it by adjusting it.

Still love the photo of the zip tie under the reeds, classic! On all 2-strokes, I listen for reed honking, or wheezing; a simple sound check that verifies the reeds are working and you have crankcase compression.

I did, I put the old one back on, same result. Magneto is full advance for sure. RE: Zip tie- ya that was a pretty interesting gift under the intake, it made the motor cheap to buy from the P/O, it runs night and day better than it did when I got it, thinking drag is slowing it down. Contemplating going CD on the ignition as well.