Questions about getting boat on a good plane?

[rdm190]

Let me start off with what I have:

Boat is a 1984 24' Wellcraft Aftcabin. The dry weight of the craft is 4200lbs with a 2400lbs capacity for gear, motor and person. It is powered by a Mercruiser 260 HP chevy based power plant. The outdrive appeares to be a MR or Alpha 1. The outdrive is fited with one of the foils to improve planeing. The prop is a Vortec, 3 blade aluim 15x17 (I assume this is a 17degree pitch on the prop?) The boat has outdrive trim and trim tabs.

I had it out for the first time the other day and it seemed to take a lot of RPM's to keep the boat on plane. I would have to turn at least 3300 RPM's to keep the boat in the mid to high 20's in the MPH (this is where it seemed to plane the best) any less and it seemed to fall on its face and then push the bow way up in the air.

Above 3000RPM's the engine uses a lot of fuel and this just seemes silly to keep the motor spun that high.

Any advice on what I can do to dial this is better would be great. I have a a 15 degree SS prop another 17 degree SS prop sitting around I have not tried. This motor has a 4600RPM redline and running above 3200 rpms is just not fuel efficent for crusing. Will this hull plane somewhere in the teens? or is just as good as it gets

Thanks it advance guys,

Ryan

 

[Texasmark]

Re: Questions about getting boat on a good plane?

No body hit this so I'll bump it up where someone knowledgeable might catch it.

All the Wellcraft boats I knew had a soft riding Vee hull which requires to be driven to get it on the water. You pay the price for the wave cutting design that is a comfortable rider. A flat bottom will plane out nicely, but ride rough.

I'm not sure (my opinion) that there is a "planed out" attitude for such a boat. You just keep pushing boat through the water and the wake convergence behind the boat just keeps moving out. Bow comes down, but not much and the wake just stays large.

Being an aft cabin with an I/O (all the weight is right at the transom) puts a lot of weight aft. Then you add folks that like to sit back there in the jump seats and it just gets worse. Course with an aft cabin you may not have jump seats.

I see that you have tabs and all to help you get her up but I'm gonna say, without being there, that you probably are as good as you're going to get.

I guess I'd say, at your 3000 rpm's look over the transom at the wake. If the water is no longer touching the transom and is forming a vee aft, then you are in fact planing and doing the best that you can.

To "plane in the teens" you have to get the arse up and that means shifting weight forward, bigger, stronger tabs, tuck the outdrive in with your trim switch.

One thing I have noticed. If you have a boat that wants to fall on it's face at the planing speed, a lower pitched prop has helped me in the past to have more control over the boats attitude at this point, there is less of a dividing line between boat attitudes, especially in rough water.

Less pitch may help you or other things may come to play where it is undesirable to do it......for example, engine rpm's will increase for a given speed (usually)........but lower pitch could unload the engine and it could be more fuel efficient at a higher rpm which would bring the boat speed back up.

I would certainly give your 15P SS a try. May be just the ticket.

Best I can do,

Mark