prop pitch?

[lbfd48]

I have a 16.5' checkmate with a merc. 150 and a alum. 23p prop. My boat runs 56mph/gps @ only 5000rpms. My question, will a ss mirage 21p prop get the rpms up where they should be, or do I need to go even lower in pitch than a 21? And will this kill my top end?
Thanks Jared.

 

[Bondo]

Re: prop pitch?

Ayuh,... What's the rpms Supposed to be at,..??

 

[lbfd48]

Re: prop pitch?

The rpms 5500-5800, I just bought a 19p laser II. So we'll see what happens.

 

[Bondo]

Re: prop pitch?

Ayuh,... Hopefully it ain't to Small,...
Is the motor of the same vintage as the hull,..??

I've got a 150hp, of about that vintage, on a stand waiting for it's project hull to come around,...

I hear they have Short Lives if not run right in the Sweet Spot,...

 

[junior1113]

Re: prop pitch?

rule of thumb eqaution -works most accurate with same prop design
old pitch x old rpms divided by new pitch =new rpm

23x5000/21=5475
23x5000/19=6050

that 19 shuold put you 5900 which is great

 

[lbfd48]

Re: prop pitch?

Okay, thanks if it to small it will work for sking and yes the merc is a 78 also.
Thanks.

 

[Texasmark]

Re: prop pitch?

Don't be surprised of your speed and rpm's increase more than you expect. Before you run it see if you can get a swap-out arrangement with your dealer. Some will swap if you just run it long enough to get your data point and bring it back; no scratches or dings.

I'm going to bet that by the time you are finished you'll be back at the 23p with the SS at 60+ mph and 5600 rpm's.

Mark