Help, wrong prop

[mac daddy 1977]

My problem is no speed now after a prop change.....I have a 1999 Seaswirl/Striper 2300 wacc hardtop pretty heavy boat, with a 2007 Evinrude 250 E-tec. the old prop only showed that it was 14 3/4" stainless steel. The boat would perform at 4800 rpm 35mph. I then lost the lower end after 370 hours, thinking that the prop may have been too much. I now have put a Michigan Wheel prop 15 x 17 aluminum on the eng. with a new bottom end. This is definately not right. Now at 5,000 rpm it will run at 21 mph. The top end now is 6,000 rpm plus.
Suggestions are needed now........

 

[ufm82]

Re: Help, wrong prop

4800 @ WOT is in the correct range but still seems low to me. That engine like 4500-5800 RPM so I think your first prop was too steep, although technically correct. As for "losing the lower end" what failed? I have yet to see a L/U fail just because of being overpropped. Engine damage yes but L/U? Overheating is all I could imagine.
Without knowing the original prop's specs it's impossible to say for certain what the cause was. However, with your current prop you are obviously underpropped as the speed is bad and WOT is too high. I doubt that prop has much cup either. I'll assume the holeshot is great? LOL
You need to go up in pitch at least to a 19. If all else stays the same that will bring RPM back to the upper 5K range. (You said WOT is 6K plus) Even a 21 will only drop you to a minimum of 5200 rpm.
Oh the prop world- great place to spend money looking for answers.

UFM82

 

[Bondo]

Re: Help, wrong prop

the old prop only showed that it was 14 3/4" stainless steel.

Ayuh,... By What Pitch,..??

 

[mac daddy 1977]

Re: Help, wrong prop

No IDEA as to the pitch of my old prop, I couldn't find any other markings.

 

[mac daddy 1977]

Re: Help, wrong prop

As to the L/U failing I was given no answer thru Sunset Marine. I had them contact Evinrude for some assistance, but they just said NO! I purshased the engine as a dealer demo with 125 hrs.on it. Had the 300 hour service completed when it was due, and then 40 hrs. later it locked up. They found metal shavings thru-out the L/E is all that I know, and there was pressure internally because they said that the oil just blew out all over the shop wall.

 

[mac daddy 1977]

Re: Help, wrong prop

4800 @ WOT is in the correct range but still seems low to me. That engine like 4500-5800 RPM so I think your first prop was too steep, although technically correct. As for "losing the lower end" what failed? I have yet to see a L/U fail just because of being overpropped. Engine damage yes but L/U? Overheating is all I could imagine.
Without knowing the original prop's specs it's impossible to say for certain what the cause was. However, with your current prop you are obviously underpropped as the speed is bad and WOT is too high. I doubt that prop has much cup either. I'll assume the holeshot is great? LOL
You need to go up in pitch at least to a 19. If all else stays the same that will bring RPM back to the upper 5K range. (You said WOT is 6K plus) Even a 21 will only drop you to a minimum of 5200 rpm.
Oh the prop world- great place to spend money looking for answers.

UFM82

I'll let you know how my new prop (14.5x19) will work next week when I test it out....