Am I under proped?

[fechtk2]

Towards the end of Last year I damaged my prop so I bought a new one, same pitch(21), I wasn't able to test it until this year, my boats WOT is recommended at 4400-4800 rpm(2000 bayliner capri 1850 3.0L) the boat is running at a solid 4800-5000 rpm is this ok to run? thank you.

 

[Scott Danforth]

Very the tach is correct

Did you get the exact same prop? Or a similar prop?

 

[fechtk2]

I'm going to say similar, it was very hard to get the numbers off the old prop.

 

[Scott06]

Towards the end of Last year I damaged my prop so I bought a new one, same pitch(21), I wasn't able to test it until this year, my boats WOT is recommended at 4400-4800 rpm(2000 bayliner capri 1850 3.0L) the boat is running at a solid 4800-5000 rpm is this ok to run? thank you.

If accurate this is ok to run. just be aware of where the rpm limit is when you are lightly loaded. and keep it from over reving.
when you are propped in the upper or just slightly above recommended wot range the boat will be better performing through out the rpm range. when I had a 3.0 powered boat I had it proped like this and it lived a long life. Pulled a lot of tubes and skiiers so it spent a lot of time above 4000 rpm

 

[fechtk2]

This reading is from my dash tach gauge if its correct.

 

[QBhoy]

If it’s genuine doing 5000 rpm…it won’t be great for a 3.0 maybe. Very few 3.0 18ft boats will require a pitch of more than a 21”. There are some, but not many.

 

[jimmbo]

Props may state the same Diameter and Pitch, but often are like Apples and Oranges.
200rpm over the WOT range, isn't instant Death for the Engine, but it might affect overall Longevity, though less than Over-propping would

 

[fechtk2]

Should i switch to a 19''p ?

 

[Stinnett21]

Rule of thumb is 200 rpm change for every inch of pitch. So if you drop 2 inches you may go up to 5400 rpm, not the direction you want to go. What QBhoy is saying above is the tach needs to be verified because something ain't sounding exactly right. Somehow verify the tach before proceeding.

 

[JimS123]

My brand spanking new SeaRay had the wrong setting on the tach. I only discovered this by adding a Vesselview system.

Data is only usable if it is correct.

 

[jimmbo]

Early in the Season, when the Air is Cooler and Drier, an engine will make more Power than during the Hotter and more Humid Days of Summer. so in July the Rpms may very well be at 4800

 

[fechtk2]

Thanks everyone, I have an external tach coming to verify the dash so i'll just keep an eye on it for now. Thanks again.

 

[Texasmark]

Rule of thumb is 200 rpm change for every inch of pitch. So if you drop 2 inches you may go up to 5400 rpm, not the direction you want to go. What QBhoy is saying above is the tach needs to be verified because something ain't sounding exactly right. Somehow verify the tach before proceeding.

For this to work, you have to have the same prop with 2" less pitch. Change prop types, suppliers and all bets are off.