I have a 1985 Skeeter Starfire 18.5". I'm currently running a 1984 150 Rude. My prop is a 14 1/4 x 21. Right now I am only getting 5000 rpm at WOT. When my boat is loaded with fuel or has full live wells I have a horrible hole shot. If I'm sitting light the boat jumps out of the hole but still can only get 5000 Rpm.

I'm thinking maybe the jack plate is set too high but to be honest I have zero idea where it should be set or what measurements need to be made to give you pros the info on where i am currently set up. I have a manual jack plate. It says Walker on the side of it. I know this motor has more to give so can one of you guys help me out here?

21 PITCH? I HAVE A 150 YAMAHA WITH A THREE BLADE 25M ON A 186 CHAMPION W/ NO JACK PLATE AND ALL IS GREAT SINCE DAY ONE. 21 PITCH SEEMS IFFY. BUT IM NO PROP GURU

It's the same prop I had on my last Rude that was the same HP. Only difference being that motor was an 1988 year model. That motor made the boat fly. I'm wondering if messed the setup up a bit when I swapped motors. This current motor runs very well, just not getting the top end I think it can do.

You have too many variables and not enough detail.
If your motor was too high it would just blow the prop out and you'd just sit back in the water. Is that what it's doing?

No, it's just sluggish out of the hole when loaded with fuel. I took it out yesterday and she ran fine and hole shot was great. I have 3/4 tank of fuel in the front tank and 1/4 full on the rear. I filled the livewell up and the hole shot was carp. One think I should have mentioned is I am now running a 36v trolling motor so two more batteries for a total of four batteries. That has to be some of the issue I would think.

I think I asked my initial question wrong. Where should I do my measurements? Am I going from the transom to the back of the jackplate? I keep reading the middle of the prop needs to be 3 1/2" below pad. By pad I assume that is the very bottom of the boat nearest the transom?

My thought is that the back of the boat is too heavy with the added batteries and full livewell. It's kind of like spinning the tires in mud. I was thinking if I went down a pitch that would help with the hole shot when I'm fully loaded.

Kingdad thanks a bunch. I've looked at probably 25 web pages and this diagram is better than anything I've seen explained.

Ok from pad to prop I am sitting at 3' and 1/2"

My prop is 3.5" off pad.

Would a change of prop help my hole shot and top end speed?

You can get in trouble arbitrarily changing props and could likely mask one problem with another. Once you get the pad to shaft measurement right, you want the pitch that gives you the motor RPMs at the high end of the operating range. Then start tweaking from there with vents, cup, etc. If I'm wrong, someone please chime in because that's what I have been taught in the short time that I've been in this game.

My Brother had a Starfire 175 with a merc 150 2 liter and with a 24 turbo prop and 6" jackplate would run low to mid 60s on GPS and no problems getting on plane. You might have a motor issue if you struggle to get on plane with a 21" pitch.

I'll check my coils and power pack again. Maybe I have a weak spark on a cylinder. I just replaced two coils and a power pack earlier this summer. I have good compression on all six cylinders.

if your at 3.5" below pad and a 21p prop that is giving the boat bow lift, then you may have some
sort of engine problem.

What about a hub slipping?

I did a decarb and it helped out a bunch. The hole shot improved and I am getting better top end RPMs.