omc prop ?

[lynnboy021]

i have a 1988 omc 5.7 and i think i have a 15x17 i think. my ? is does that prop sound right for my 23ft sunbird? i did a test run on the river and at 4000 rpm my boat was only going around 10 mph...

 

[steelespike]

Re: omc prop ?

Doesn't add up.While the 17 probably isn't the right prop at 4000 it should be running
25-30 mph.At 10 mph it wouldn't even be planing it would likely be bow high and struggling.
Either the tach is wrong or the speedo is wrong.

 

[Robbabob]

Re: omc prop ?

Was the 10 mph your water speed or GPS speed? meaning, on a river headed up stream against a wicked current can cause GPS speed to be really slow. This is a far fetched thought, but a possibility.

Next: is your prop severely damaged?

Do you have experience using the trim?

Sorry to ask these type of questions... We don't see you or your prop and can't assume anything.

By the way, what are you using for your speed monitoring? if GPS, then okay, my first point could still be valid. If using the Pitot tube (run to the stern), it could have debris blocking the water pressure. As Steel says, the 17" seems a little low in pitch; unless you prefer tubing and skiing to top end. But the 4000 RPM at 10 MPH does not make sense.

Were you at WOT and only achieving 4000 RPM?

Good luck!

 

[lynnboy021]

Re: omc prop ?

yes my bow was way up it did not want to plane. i had the trim all the way down and i was playing with my trim tabs but my bow was still up. i dont have a pitot cuz its gone and my prop is brand new well i have 2 brand new that came with the boat. there was a old prop i think it was 15x17 and a brand new one 15x17 and also a brand new one i think its 15 1/2x17. maybe its not the prop maybe its the carb? i just did a 100% tune up on the motor. maybe tomorrow i will do another test and i will let you guys know

 

[Kiss4afrog]

No acceleration

No acceleration

I know it's been so long you most likely have a different boat but what did you find out about the problem you were having. 4K rpm and 10MPH !!!
Was your prop a 15 X 17 or something else?

 

[Howard Sterndrive]

Re: No acceleration

Re: No acceleration

sounds like the prop hub is slipping - try another prop