Mercruiser prop help

[holloway]

5800 rpm - I believe this number to be true, idles at 600 and sounds right.
42 mph- gps
14.5x19p
alpha 1
5.0l
1989 20' Maxxum

I know i need to get the rpms down, but the calculator I was using to figure prop size is telling me a 24p is what I need. Does this sound right? The prop selection I've looked at has offered 14.2 x 23, close as I can get. This is really frustrating to me, I wish someone would tell me, " yep this is what you need".

Thanks for any help.

 

[nlain]

Re: Mercruiser prop help

I am not going to tell you to do it but, 4 inches pitch at approximately 200 rpm per inch should bring you to approximately 5000, that is if you are really turning 5800 now, it should be screaming if you are.

 

[Dhadley]

Re: Mercruiser prop help

Yep, as long as your current prop is in good shape and not just slipping. A 23 -25 will certainly get you closer to the desired rpms.

 

[Bondo]

Re: Mercruiser prop help

Ayuh,... It Sounds like you've got the Wrong gear ratio in your outdrive.....

 

[holloway]

Re: Mercruiser prop help

Ayuh,... It Sounds like you've got the Wrong gear ratio in your outdrive.....

That is possible too. I have trim tabs on it and it has a great hole shot, just screaming at WOT. I have a tach/dwell that I will check the onboard tach with, but the rpms are high enough at WOT to make me nervous checking it out.

I can't find the serial on the drive, but the numbers on the motor are

Motor OC474354
Transom Assembly OC483978

I really appreciate any and all help guys..

 

[Tail_Gunner]

Re: Mercruiser prop help

5800 rpm on a 5.0 v8?????......24p on a heavy boat...time to go recheck your tach. somethings afoot here.. That a 180-200hp motor on the back of your tach there should be settings for 4cyl 6cyl 8cyl make sure there right.