Prop pitch help!?!

[jonoman69]

I have a 1999 17.5 bowrider bayliner capri. The boat has a 3.0 merc in it. I am currently running a 21 pitch aluminum prop, my rpms max out at about 5100 and at about 40 mph. I don't do a whole lot of water sport, only on occasion. I'm just trying to figure out if I should change my pitch size? And what to?

 

[dmweyrauch]

Re: Prop pitch help!?!

If you go with a 23 pitch it will lower your rpm at least 300, I would check the tach.

 

[jimdogg1269]

Re: Prop pitch help!?!

i have a 2000 17.5 capri. 3.o merc,, im running the 21p prop, my rpm is right around 5000 and the speed on gps is 48 with me, the wife and dog in the boat,, is ur speed with gps or the speedo

 

[jkust]

Re: Prop pitch help!?!

Your rpm's and speed sound like those of a lower pitched prop. 5100 rpms with a 21 should get you moving faster than 40. Take a look at the prop slip calculator and verify with a gps if you haven't done so.

 

[not enuf toys]

Re: Prop pitch help!?!

what are you trying to accomplish? what gear ratio is your outdrive?

 

[Brewman61]

Re: Prop pitch help!?!

You really don't mention what your complaint with this setup is, or what you hope to acheive by changing out the prop.
That'd be helpful to know.

 

[jonoman69]

Re: Prop pitch help!?!

Okay, it is a 21 pitch merc prop, the gear ration is 2.0 assuming that is what the 2.00r on the drive means. Basically I am using the boat just for cruising around, would I gain anything by changing the pitch up, perhaps a bit more top end, and lower rpms at cruising. Also I dont like that fact that I can over rev it when I open it up.

 

[DragonBlod]

Re: Prop pitch help!?!

I think your tach is wrong. By almost everyone on here, they say that the 3.0 screams when at 4000 rpm and it should sound like your motor is gonna blow at 5k. I had the 3.0 until 2-weeks ago on a 17.5 Marada shallow v-hull, and at 4k I was clipping and the motor was pretty noisy. I would check your rpm's with an external tach, and do as mentioned above, check your speed with a GPS. Unless you have a shallow hull like the Marada, you won't get huge speed with the 3.0. Also is your boat 120, 130, 135, or 140 hp? My 19P prop with knicks in the blades got me over 40 easy with the 135hp but again that is a shallow hull.