Boat will not plane!

[TheChugBoat]

Ok so my boat won't plane...its a 20ft wellcraft eclipse with a brand new rebuilt 4.3L. I know the engine isn't the problem because I had the same issue last year with the older engine. The only time I can get it to plane out is when someone sits on the bow of the boat.

Im thinking it is a prop issue. Not sure the exact prop I have on there now but could anyone steer me in the right direction of what prop I NEED? Im unable to hit WOT right now, still in the break in period...but even at 3800 RPM's it will not plane without weight added to the bow of the boat.

Im also thinking about buying Smart Tabs...Ive heard nothing but good things about them.

 

[HighLineCBR]

Re: Boat will not plane!

your boat should plane fine. It seems like a prop issue. I would search for a prop. Do a Google search on "find the right boat propellar" or something like that. There are many sites out there which will help you choose the right prop.

good luck!

 

[cpubud]

Re: Boat will not plane!

trim tabs will help.but you need a lot more info on the motor to lead you in the right direction.was the outdrive rebuilt or replaced,if so what gear ratio is in it. current prop size.all have an effect on your problem. good luck with it.

 

[TheChugBoat]

Re: Boat will not plane!

The outdrive hasn't been touched too much. Other than normal maintance and replacing gaskets. I believe its an Alpha one...gen 2 rings a bell...not positive though.

 

[QC]

Re: Boat will not plane!

We can help right here with a prop, no need to search the net. Prop calculators are often off some. But . . . this is too early to discuss that!

Why can't you run to WOT RPM? Break-in period allows that for short spurts. How many hours on it? What pitch is on there now? When you say "brand new" and "rebuilt", what is new and what was rebuilt? Sea level? I think I'd go with 3% tinted windows, that could help too . . . Seriously though, there is no guarantee that engine is running right at this point, and we don't know if you are trying to swing 26 inches . . . Need the info . . .

 

[codertimt]

Re: Boat will not plane!

I'd also like clarification of your scenario. Is your motor turning 3800 rpm while still attempting to plane? All while at partial throttle? It seems to me that, if you're making good power, unless something is slipping somewhere(ventilation, spun hub, slipping engine coupler) it shouldn't be possible to be turning that rpm and not running a decent speed.

More information would help...

Gear ratio should be 1.84:1 for that vintage if it's the correct outdrive for the 4.3. Look for a stamp on the outdrive to confirm.
Pull the prop and look on the hub for a stamp for size.
Has this boat/previous motor/prop combo ever performed correctly?

 

[TheChugBoat]

Re: Boat will not plane!

There is approximately 2 hours on the rebuilt engine. Ill have to wait until I go back to the marina to gather all the prop information. The RPMs read 3800 and still not on plane...I can get on plane if weight is added to the tip of the bow. Itll stay on plane even when weight is removed...and it seems to be running perfect...once it's on plane.

Obviously Ill need more info before any useful information can be given. Ill try to swing by the marina tomorrow morning and get the prop diameter and pitch and check outdrive stamp.

 

[QC]

Re: Boat will not plane!

"Rebuilt" by whom? Rebuilt could mean a set of heads, or a complete overhaul. Neither would usually involve the fuel system, so there is no guarantee that this engine is actually running right. It may have a pristine bottom and top end, but rarely is performance tested prior to delivery of a rebuild. If this was a Merc "crate engine" with a complete fuel system I would generally assume it is running right, but even that is no guarantee.

Also, I don't believe for one minute that the engine would turn 3800 RPM before planing. There is something wrong with your numbers . . . Props just do not slip (hydrodynamic slip, not mechanical) that much. You need to:

1) Verify the tach is correct
2) Verify the prop pitch, diameter (less important than almost anything here), material, make, model, and number of blades
3) Confirm the gear ratio
4) Confirm what your "rebuild" is . . .
4) Confirm what performance tests were done along with the rebuild
5) Confirm the WOT RPM, normal load, trimmed properly for max top speed.

With ALL of this info we can help you get this right, or at least confirm whether it is wrong. Good luck!!