Evinrude 135 1974 Prop help

C

ckraker

Petty Officer 2nd Class
Joined
Apr 21, 2007
Messages
140
I just put my Dad's old boat in the water for the first time in almost 10 years. I just put a new tachometer in it and we had actually just rebuilt the engine shortly before we stored it. When properly trimmed we actaully got going just under 40 MPH, running about 4800 RPM's. It is a fairly heavy old 16' fiberglass boat, so I was pretty impressed. It took off pretty fast too. My dad says we should be getting up to around 5500 RPM's, Should I consider getting a different prop? I have a Michigan Prop. #004 the manufacturers guide says we should have a 004 or a 005. How much of a difference would a 005 make? I'm not up on prop lingo, so I'm not sure if I need to try a bigger or smaller prop. any suggestions would be great.

Is anyone else running with a max of 4800 and calling that good?
 
C

ckraker

Petty Officer 2nd Class
Joined
Apr 21, 2007
Messages
140
Re: Evinrude 135 1974 Prop help

I just looked it up. my 004 is a 13" with 19 pitch and the other prop the 005 is a 12 3/4 with a 21 pitch. Would it bring my rpm's up if I put a 21 pitch on, or would it bring them lower?
 
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ckraker

Petty Officer 2nd Class
Joined
Apr 21, 2007
Messages
140
Re: Evinrude 135 1974 Prop help

I know RPM's Can be between 4500 and 5500, Is there an advantage that I would have by changing the prop and getting to 5500?
 
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steelespike

Supreme Mariner
Joined
Apr 26, 2002
Messages
19,069
Re: Evinrude 135 1974 Prop help

Your speed isn't too bad but:
Before changing props is the motor broken in?Is the antivent plate,just above the prop,visable on plane? Throttle opening all the way.Timing set right and advancing as it should.Does the boat respond to trim?What year and brand boat.May be able to look up the weight.Is it a deep V?It seems to me that the 19 would be pretty close to what you need.Diameter is a secondary consideration.As pitch goes up diameter generally goes down. A 1" pitch change will get "about" 200 rpm change.
lower number increases rpm. A 17 might get you to "about" 5200.It is generally considered that 5,500 is the least you should shoot for with todays doctored fuels.
imo Any pitch below 17 would be extreme for your setup.
I think you can get more out of the 19 then decide on a prop change.
 
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