Help With Prop Selection

[QBhoy]

I fixed the hooks in front of the transom, using metl-weld epoxy as a fairing compound. It looks like the previous owner
tried to use roller bunks, there are concave areas evenly spaced on the bunk line. I will have to fix them over the winter.

The previous WOT was 32mph@5800rpms. Now it's 37mph@6000rpms.

Hi

Is the rpm from the smart craft ? You’re still way out compared to mine.
That’s some prop slip you have.
I’m now running a 20” enertia. She will pull 43 any time and 44 gps on a couple of occasions. This is at just under 6000 rpm. The limiter is just beyond that slightly. That’s great going the way I have it set up...but if you are getting 6000 rpm with a 21”...and only 37 (is it gps ?) it’s likely a pretty high prop slip. Haven’t checked though. I think I was about 7-9% slip last I ran my numbers.
regardless. They are amazing engines eh. The sweet spot seems to be around 3700 rpm on mine. Goes really well at that rpm and uses literally hardly any fuel. Shows about 1.7 miles per litre used at that. Incredible. Think she’s at about mid 20’s mph or so at that.

 

[QBhoy]

Just checked. You’re at a pretty awful 26% slip. Seems something still isn’t just right.
Is the speed GPS and is the rpm from smart craft accurate gauge ? If it’s not...that would explain it.
If you are getting 6000 rpm with a 21”...I’d expect you at mid 40’s anyway.

 

[JFZ]

I agree, I think it's the rest of the imperfections in the hull, 2 or 3 more. Also I was alone and couldn't check the
AC plate when it was on plane, to check the engine height. I'm going to fix the rest of the hull this winter. In the spring I'll see how it runs and I'll definetly keep the enertia in mind.

That was gps speed and the tach in the dash. I think it's right because of the idle speed and the rpm change when
I change prop pitch.

 

[Texasmark]

It may take some time for you go get your arms around all the monsters. On this 2002 rig I bought this year, I just found out that my fuel filter was clogged big time....little pieces of tan plastic.....liner of fuel hose. (B1-15 is supposed to be the best and I have that on now and have flushed the lines). Now you go back to all the diddling I have been doing for the last 5 months and coming up with funny answers and toss in a clogged fuel filter and daaaaaaaa.

Got the new one today and will install tomorrow. Sometime in the week will get out and see what's different and where I "puked" money chasing a ghost.

Good luck.

 

[JFZ]

Yes it does take awhile. Good luck with your boat.

Thanks to everyone for the help!