Prop help

[Thebone]

I have a 17ft sea pro with a 13 1/2 ? 19 prop but my RPM's at WOT run Around 5800 RPM would a 21in prop help bring the RPM down running a 2000 mercury 75hp

 

[Sea Rider]

Was 5800 wot rpm achieved while lightly, medium or heavily loaded ? What's the max wot range for that OB ?

Happy Boating

 

[alldodge]

If this is a 4 stroke WOT should be between 4500-5500 rpm. So 5800 is a bit much, so going to a 21 pitch prop should drop the rpm around 400 rpm's.

That said, are you sure your not over trimming? The manual shows it should be within the limits if you boat weights in around the 1600-2400 pound mark

 

[Thebone]

It's a 2 stroke loaded down boat around 2000 pounds running 33mph trimed perfect

 

[alldodge]

IF (and I do mean if) I have your correct motor (no serial number provided or anything else except 2 stroke 2000 model) then your WOT rpm is 4750-5250

Now if your tach is correct when it says your turning 5800, then the 21 pitch will drop by about 400 rpm.

http://boatinfo.no/lib/mercury/manuals/75-90-100-115-125.html#/8

My thought is that your tach may not be correct because 5800 is quite a bit above your max rpm. You might want to try a hand held tachometer before changing things.

Hope an outboard guy come along and provides some input

 

[flyingscott]

IF (and I do mean if) I have your correct motor (no serial number provided or anything else except 2 stroke 2000 model) then your WOT rpm is 4750-5250

Now if your tach is correct when it says your turning 5800, then the 21 pitch will drop by about 400 rpm.

http://boatinfo.no/lib/mercury/manuals/75-90-100-115-125.html#/8

My thought is that your tach may not be correct because 5800 is quite a bit above your max rpm. You might want to try a hand held tachometer before changing things.

Hope an outboard guy come along and provides some input

I agree double check the tach. If it is reading correctly then change your prop because if it's right you are going to need to go up 3-4" of pitch that's a lot for that motor.

 

[Thebone]

Yes I am going to check the tach and yes WOT SHOULD NOT GO OVER 5250 Thanks

 

[steelespike]

Definitely check things out but I think it is unlikely It would over rev with a 75. I think it is rated for about 100 - 115 hp.
Does 2000 lbs include the boat and motor?

 

[Sea Rider]

Any under powered OB will over rev if too low pitch prop is selected, worst if powering a light boat while boating lightly loaded.

Happy Boating

 

[steelespike]

He is running a 19" its highly unlikely to over rev on that boat.