5.7L WOT @ 4200 rpm with 5 blade prop

[russell_poling]

From what I've read on this site my WOT @ 4200 seems a little low for I/O 5.7L.

I bought the boat a few months ago and it came with the 5 blade S/S prop. I'm not sure about the pitch, is it written somewhere on the prop?

Anyways, my top speed with just three adults in it is only 50-55.

My boat is an 84" Exciter 19'. I think it should be faster and wonder what changes to the prop would do for my top speed. It comes on plane quickly with the prop it has now, is this the reason for low top speed?

Any advice would be great.

Thanks

[Big Dave]

Prop pitch should be stamped or cast on the hub at the nut
some aftermarket props stamp pitch #'s on the outside of the hub.,
need those #'s to help at all

Rpm sound really low. how much trim are you using?
how about a compression test on engine?

[russell_poling]

Thanks for the reply.

It's got a 22 stamped on the side of the prop.

I'm a goober and new to boats, Once I figured out that you have to trim it out at top speed, my RPM went over 5,000 and top speed is close to 65mph.

I've tried to read about proper trimming but haven't found anything worth while, are there good/bads to trimming too much or too little?

Thanks again Big Dave

[Chris E]

Check your engine manual, but i beleive that engine should be running 4400-4800 rpm at WOT, might want to go up in pitch an inch or two to bring the revs down to where they should be - overrevving is bad! The five blade should give good hole shot but your top end may suffer, see if you can find someone that will let you play with some different props to see how they perform on the boat - the differences can be quite substantial

[Big Dave]

on stern drive boats, there is a trim limit switch on the gimble housing outside where the drive pivots. That keeps the drive from going too high when in gear. It is adjustable but too high and the prop will start slipping and you will loose speed.
Did you like the difference in feel when you started trimming up?
I have never felt as much difference as in a Checkmate. They seem to love positive trim. Really makes the boat feel much lighter.

[russell_poling]

Thanks for the info guys, I'll try to get the RPMs down by going bigger with the prop, one of my neighbors has an 87' Mate with a four blade I'll see how nice he is next weekend.

Big Dave, the difference with it trimmed up is awesome, I should have bought Boating for Dummies. I've paid for a few rookie mistakes since I've gotten the boat.

[Big Dave]

Its not you, Its Checkmate Boats.
Everyone I have driven responds more to trim than most any other brand boat. I really get a kick out of the change in boat feel when you start hitting that up button.