2004 38 lightning prop question
 

I tested a used pair of 31 labed 5 blade maximus props today and the results were:

4900 rpm 89 3/4mph

3 people 30 gallons fuel 65 deg. weather bravo xrs 2-525's
what can I do to squeeze out enough rpm to hit rev limiter or close to it and maximum mph?

I also noticed a slight vibration like they may need to be balanced. (look ok but vibrate slightly while getting on plane)
Is this a big deal?

That vibration getting on plane is probably cavitation. Check your tab settings and drive settings.

you will need to re-pich the props you will lose another 100-200 rpm when it gets hot. I would guess you need 29p to get to 5400 rpm

I just tested a set of 28P Maximus blades on my 42' Fountain with 525's The hole shot was better, mid-range acceleration was improved, and top end was at 82mph, around 5200 rpm's. I would think these would be close for your application. I am going to do a little more testing with 1/2 load of fuel and 2 people in warmer weather to see where I am before I have them labbed by Bblades.

I have a like new, test only set of Merc labbed 28 Maximus coming in today if interested.

Jamie

You will lose a small amount more rpm as the humidity level increases. However, there is most likely something that can be done these props to get them where you need to be. By this I mean closer to the rev limiter. There is no reason to be on the rev limiter. If you can get to the low 5000's, you will be fine. The RPM range for the engine is 4800-5200 with a rev limiter at 5400.

Determine the casting the propellers were made from. Is it a 32 or a 30? Also, who did the Labbing? We may be able to use these props to get to your goal.