New prop performance and suggestions

[b_lish1966]

I have a 1976 starcraft(tri hull) 15ft with a 1985 or 86 Johnson 70hp, I put a 14.75 x 13p solas prop on it recently and took it out and ran it. On my first run there were two adults and the boat ran about 32mph at 6100 rpm's and then went out with two adults and 4 kids, the boat ran about 28/29mph at 6020-6100 rpm's, was happy really with the performance overall, jumped on plane nice and could back off quite abit and hold plane while tubing, I guess my only question is are the WOT rpm's to high,should I be concerned at the range or is it ok.

 

[steelespike]

Re: New prop performance and suggestions

If it is an 85 the hp is rated at 5,000 I wouldn't exceed 5,500.
If it is an 86 it is rated at 5,500 6,000 sounds more reasonable.
do you have a model number.I'm consertive and would be more comfortable to back off to 5,800 or so.Someone will no doubt be along with more specifics.

 

[Dhadley]

Re: New prop performance and suggestions

Even if it's the 3" bore 1985 70hp you'll be OK at those rpms. It has the big rods and should hold up well. Those numbers sound good, especially for tubing and watersports. Obviously if you were looking for another prop for better top end then you could go with more pitch.

 

[b_lish1966]

Re: New prop performance and suggestions

Here's the Model #J70TLCUR and serial #R 7446288, which makes it a 1987 I believe. If I'm right then the rpm's are on the high side but within a safe operating range I think. The motor does not have power T/T but manual instead, I didn't have the motor all the way down on the last run so I'm going to drop it one more hole and see what the effect will be.

 

[steelespike]

Re: New prop performance and suggestions

Appears to be an 87.Bringing it in a notch will probably slow it some but make planing easier.