Prop Pitch Selection 40hp 1968 Johnson

[David S]

Here are the specs: Model RKL-30-C Ser. J2928781<br />15' 1968 starcraft V-hull aprox rig weight and gear probably not exceeding 1200 pounds.<br /><br />The current prop is a 101/4 X 11 pitch<br /><br />Unfortuantely I have never checked WOT RPM. <br /><br />The problem is that the boat seems to run slow with the motor wide open. Im guessing about 15-18 MPH. Also it is very slow to get out of the hole. The motor revs slowly on WOT until it is out of the hole, then it begins to rev up and the boat sucessfully goes to a decent plane.<br /><br />I tuned the motor and had rebuilt all electronics on powerhead. The motor runs very smoothly and never even skips at high or low RPM's. <br /><br />With prop running about $80 a crack Im not sure I want to experiement by buying a 10" pitch or 12" pitch to see wich works better.<br /><br />Realistically, Im happy the way the boat performs, but I want a spare prop and it would be nice to have one that pushes the boat a little faster. (Dont we all)

 

[FlyBoyMark]

Re: Prop Pitch Selection 40hp 1968 Johnson

We can't really help you untill you let us know what your rpms are, only guess...Wanna speculate with $80.00? Your engine is about 35 ponies at the prop. If your guessing your weight correctly, the boat should do about 27-29 MPH. You might want to do a compression check and check the spark advance and throttle throw along with possible carb cleaning job if your boat is that slow.(Don't forget decarb on an old piece of iron like yours...) Are you running 50:1? I would weigh the boat if at all possible so that more exact answers can be given. I suspect your weight is off a good bit if your engine is running as good as you say it is... A good tach is "Tiny Tach" for your motor.<br />Go to this site for Tiny Tach:<br /> web page