Prop/RPM Question

[j442w30]

Hello All,

I got my boat out for a run today and after setting the correct engine height so the anti-ventilation plate was about 1.5 inches above the bottom of the boat the difference was like night and day. No more porpoising, the boat just hooks up and goes. My problem is at full throttle (the engine is a 1993 Mercury 40 hp outboard with a 1.83:1 lower unit) I am getting around 6000 rpms and according to my service manual I should be maxing out at 5500 rpms. The propeller I currently have is a 13 pitch Aluminum quicksilver on my 14ft aluminum runabout. Do these engines have rev limiters? Or is something wrong with my tach? It seems to work fine, it doesn't jump around or anything, its on the 5P setting and the rectifier is new. I don't want to over-rev my engine but would this prop be okay for pulling waterskiers? I was planning on doing the two propeller setup, one for pulling and another for top speed. Can anyone recommend a stainless steel propeller for top end? I was thinking I needed something in the 16 - 17 pitch range. Any and all advice would be greatly appreciated.

Thanks

 

[Silvertip]

Re: Prop/RPM Question

The prop you have would be fine for water sports and for use when you are heavily loaded. Boats have throttles so you can pull back a little if revs get too high. For speed, you need to add some pitch. Going from 13 to 17 is too much as you would be dropping about 800 RPM. A 15P would put WOT revs at about 5600 assuming the prop is the same type you currently have.

 

[boat1010]

Re: Prop/RPM Question

I agree with Silvertip. You never said if you were alone in the boat. That makes quite a bit of difference. If you put two or three more people you will drop your RPM usually. It's imposable to get a prop that will give you the Exact RPM in all conditions. You need to prop the boat for what you are looking for. Good hole shot for pulling up skiers or a little more top end. Good luck.