prop too tall.

[beertk]

Hello I got a 16 foot sea nymph boat with interior with a 1972 50hp motor on it. I just bought a 15 pitch prop for it. It is a little sluggish accelarating. Also it only does 18 miles per hour. I think it should go faster. Would you say the prop is too tall.

 

[JB]

Re: prop too tall.

My first thought is that your engine is down on power, Beertk.<br /><br />What rpm are you reaching at WOT?

 

[beertk]

Re: prop too tall.

I have not checked yet. I think im under 4500 though

 

[ledgefinder]

Re: prop too tall.

15" should be just about right for the 50hp twin on a 16 footer. <br /><br />That has a 2.66:1 lower unit, so the 15" is equivalent to just under a 12" on the more common 2:1 lower unit. (OMC V4s are 2:1, as are Merc 50 & 65hps, etc.). <br /><br />I second JB - motor may be down on power. How's the compression?

 

[beertk]

Re: prop too tall.

I just bought an oem brand new aluminum prop. the box says as follows.<br /><br />pn 177151<br />alum 45-115hp, v4<br />13.75x15RH<br /><br />Do you think this boat should do more than 18 mph

 

[walleyehed]

Re: prop too tall.

"YES" as stated above, sounds like you need to do a compression test...do you have the meens to do so???<br /><br />391198 is the current P/N for 71-74 2-cyl. 50's<br />with the dimensions you give. I don't have my book in front of me to tell if thats the old P/N

 

[JB]

Re: prop too tall.

I estimate that you should get close to 30mph with that rig in good running order, Beertk.<br /><br />I also estimate that a 15" prop would be very close to right for your boat.<br /><br />I suggest that you proceed as though you have an engine down on power, maybe only making power on one cylinder.<br /><br />Good luck.