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propeller help needed:  150HP Evinrude 1993

All,

I have recently purchased a 1993 Stratos 274 DC bass boat, 17.5' long. It came with what I was told was a stock motor -- 150 HP Evinrude.

The seller had changed the prop to a spare he had -- 25 pitch, 13.5", 4 blade propeller. The boat now has a hole shot that takes a long time, bow wayyyyyy up until you nurse back power a bit to bring it on plane. It generates 4400 rpms and reaches about 50 mph via gps (MFG range is 4500-5500 RPM at WOT). It has a jackplate and I've raised it from about 6 inches to about 4 currently.

Does anyone know what the original prop would be? If not, does anyone have any advice about what I should try next?

What I've read online suggests this:

*get RPM's up first -- and that reducing pitch by 1" = 200 RPM's on average. So I'm thinking dropping pitch by 3-4" is the right place to be, or in my case either a 21 or 22" prop.

*blades -- 3 or 4?? I have no idea what the difference might be.

*diameter: I have no idea.

Thanks much!!

Please reply to readmeray@mac.com

 bleezle
May 22
2006
I have a 225 ficht on a 26' v bottom aluminum workboat and at 6000rpm the 3 blade only gave me around 35mph and the 4 blade again at 6000 gave me 42 mph, I was amazed because I thought the 3 blade would give a higher top speed.

"bleezle" <readmeray@mac.com> wrote in message

mark
May 23
Were they the same pitch and diameter? Bishoop
May 23
Of course not.

Rob

 trainfan1
May 23
I don't belive so either. With the facts as they were presented, the laws of physics would have to be rewritten.

In probably 99% of all installations a three blade with the same pitch (all other things being equal) will be "slightly" faster than a four blade.

Bishoop
May 23
I am no expert, But I think the 3 blade would run faster with equal pitch. This is due to the added resistance of pushing the forth blade. On my old cuddy (gee I miss it :-) I had a 17 on it and heard the boat would plane at slower speed with the four blade. Merc suggested since I was trying to keep the rpms the same to go to a 16 inch pitch four blade as a direct replacement for a 17 three blade.

Tried it out and the boat did plane at a faster rate, I am not a speed demon so I really did not try to see where the top end was.

Retired the four blade to the "spare" shelf as it made holding the bow up rather difficult - ie the boat ran with the stern up high and trimming it would not help.

Your mileage may vary, this boat had a wide stern for it's length and 18 degree deadrise at the transom.

Capt Jack R..

 Jack
May 23
Does the prop have black rubber plugs on the side? If it does, you might want to try venting it. Google the group for plenty of info on that.

You can also try the Mercury prop selector, the brand makes little difference:

http://sites.mercurymarine.com/portal/page?_pageid=126,53050,126_53052&_dad=portal&_schema=PORTAL

Dan

 Dan
May 23
   
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