Motor Height

[mjash]

Had the boat out today...Ran just about flawlessly after Changing power pack and rebuilding carbs. <br /><br />My next goal will be getting the boat/motor set up correctly. My AV plate sits about 2 1/2"-3" below the bottom of the transom. WOT produces 4700-4800 rpm @ 34mph(GPS). <br /><br />I know I can get more from this motor...just not sure how. Compression is just over 115 on all cylinders and Current prop is a Michigan SS 13 1/4x17. <br /><br />My goal is 5800 rpm, do you think moving the motor up 3" will get me there. Also, what kind of speed should I expect @5800.<br /><br />Thanks for the help,

 

[Walker]

Re: Motor Height

I'd definitely raise it 3" to start with. Don't know if you'll pick up 1000rpm, but you will pick up a noticeable amount.

 

[mjash]

Re: Motor Height

Does anyone know the formula for rpm vs. speed

 

[MGuckin]

Re: Motor Height

Slip <br /><br /> Various speed computations discussed here. Old post. <br />Motor definately must be lifted. I would start with even or just above.

 

[CFronzek]

Re: Motor Height

RPM to speed calculations for aboat would have a lot of fudge built in. The prop is pushing against water and the ability to drive the boat foreward depends on how slippery the hull is and how heavy the boat and it's occupants are. Nowdays speed checks by GPS are common and fairly accurate.