RPM'S

[Cool It]

Hello,<br /><br />I have a 1988 22 foot W/A with a 5.0 Mercruiser Alpha one.<br />I seem to have a problem when I try to push past 3200 or WOT. At 3200 boat runs nice smooth but only running at about 20 MPH When I push higher the RPMs get jumpy and when I push Toward WOT the RPMS Start to come close to the red- seems to be winding out. I dont Know much about my Prop the size/pitch etc. Can this be a prop problem and how do I know what size and pitch I need. How do I know what size and pitch I have Now !! Any help would be Great I hope I have Explained this properly..<br /><br />Thanks COOL IT !!!

 

[metwrench]

Re: RPM'S

What Size Prop and Picth do you have ? When you WOT, explain what do you mean about " Jumpy" ?<br /><br />Prop CAN be your problem, But unless someone Physically changed it to a Lower size I might think something like the Dog teeth in the Lower unti are slipping.

 

[Northern Eclipse]

Re: RPM'S

Without knowing what pitch prop you have, its hard to comment, but you should be able to spin a 14x19p or a 14 1/2x 17p, 3 blade, its also possible that the rubber hub is weak in the prop, and slipping, this is noticed when engine rev's up freely and boat speed does not increase very much or at all. If you look on the outside of the props hub, in between the blades, you should be able to find a stamped number in the casting such as 15p or 19p, that will be the pitch, If you are unable to find any numbers, take the prop to any prop shop or marine repair they should be able to help you in most cases.