low rpm cant get on step

[toolsinbox]

454 with alpha 1989 21 ft scarab

I put the boat in the water for the first time. drove it to the dock on plane at about 28 mph maxed out about 3000 rpm with slight surging put the kids in at the dock and three adults including me and couldnt get on step. I thought of fuel but it had an 1/8 tank when I got it and then I put it almost to 3/4 tank before putting it inthe water. Somone said put isopropel in to help burn off any water that might be in there. It has a fuel filter that resembles an oil filter that I thought seperated the water out. Thats what I thought anyway. It runs almost as if it was being choked but idles great. Tommorow I may try running it with out the air cleaner. Not sure where to start. I guess plugs and wires maby. The thing idles great just wont turn any rpms. I have a three blade prop on it with no pitch number on it I think it says Paranna on it. I have a 4 blade as well I guess I could try that. Any help would be great.

 

[havasuboatman]

Re: low rpm cant get on step

You maxed out your boat rpms at 3000? Am I understanding that correctly? Then when loaded down it wouldn't plane?
If that is so, you probably have too much pitch on your prop. That engine, with the correct prop. should reach between 4800 and 5200 RPMs when run wide open throttle.
That fuel filter you spoke of is a water separating fuel filter. It has to be changed annually. If you suspect water in your fuel replace that filter. If it gets too much water in it, it will start starving the motor of fuel at high RPMs which can cause surging.

 

[Don S]

Re: low rpm cant get on step

Since your 454 has an Alpha drive, your engine and drive are an 88 model. With the Alpha drive you should have a Max WOT throttle range of 42 to 4600 rpm. You will not find a prop that will give you that much of a change.

Here is a list of possible causes for Low WOT.

Engine Won't Reach Operating RPM. Check

1. Fuel condition. Type and Octane possibly old fuel
2. Propeller pitch or diameter, damaged blades
3. Restricted fuel pickup tube or anti siphon valve Fuel System Test
4. Crankcase oil volume, high oil level can cause aerated oil and lifter collapse
5. Marine growth on hull and outdrive
6. Wrong gear ratio in outdrive
7. Restricted carburetor air intake (clogged flame arrestor)
8. Restricted exhaust system (broken exhaust shutters/flappers) in engine transom shield or drive
9. Poor cylinder compression Compression Test
10. Carburetor defective, or wrong type.
11. Fuel pump pressure and vacuum
12. Boat overloaded, improperly loaded, or improperly trimmed.
13. Engine Overheating
14. Engine timing and ignition system operation
15. Remote control cables and linkage for proper travel to open throttle plates fully.

 

[toolsinbox]

Re: low rpm cant get on step

Thanks Don I started reading that section after my post. I guess I need to do the filter just here at the lake I have no acess to filters is there a way I can clean the one I have to temp use for now? Does it unscrew like an oil filter? I have a fuel pressure guage mounted just past the filter what are the fuel pressure readings I should be getting at normal opperation? I have the machanical fuel pump. Thanks.

 

[Bondo]

Re: low rpm cant get on step

Ayuh,... It's just like an oil filter,... Pull it off,+ dump it into a clear container,..
You'll probably be able to See the Water...
4/6psi at the Carb is normal...

 

[toolsinbox]

Re: low rpm cant get on step

The fuel filter was clear and clean and went out and the fuel pressure was just under 6 but its gone from bad to worse I now have water in the oil so I am shut down. Had to be towed in. I am not sure where to go from here except after the weekend I will take her home and start wrenching. Must be the head gaskets. I saw steam comming from the risers attached to the valve covers so I shut the engine off. Checked the oil dip stick and it is milky so I know what that means. Good grief what next?