4.3L OMC will not run WOT

[zeek7pc]

I have a 1987 OMC 4.3L cobra in a 22 foot Sea Ray Seville mid cabin. Here's my problem. I have a 13 pitch by 15 1/2" and a 17 pitch by 15". Neither prop will tach out the motor, the best I can get is 3700 RPM with the 15 and 3600 with the 13. Motor starts, idles, and runs great. Any suggesstions? Thanks in advance for any replies...

 

[Gary H NC]

Re: 4.3L OMC will not run WOT

When was the last time it had a full tune up? Points,rotor,cap,wires,plugs and timing set? All fuel filters changed ect...
Also hold the choke plate open with the engine off and have someone advance the throttle.Look down the carb to verify the plates are fully open at full throttle.

 

[zeek7pc]

Re: 4.3L OMC will not run WOT

Thanks for the super fast reply!! I've checked the carb, it will open all the way. I gave it a tune up, didn't help. Any other ideas? Or does this motor just not have enough power to push this big boat that fast?

 

[df909]

Re: 4.3L OMC will not run WOT

I agree with that it sounds like it's being starved of fuel. The RPM's should be pretty different between both props. I'd inspect the fuel system from the tank to the carb & making sure that there is no debris in the line itself. Good luck.

 

[Bondo]

Re: 4.3L OMC will not run WOT

Ayuh,... Has the boat Ever run right with this motor,+ drive,..??
Has the drive been Changed,..?? Is it the Right Ratio,..??

 

[Don S]

Re: 4.3L OMC will not run WOT

List of possible causes of low WOT (Wide Open Throttle) rpm.

In no particular order

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.

 

[zeek7pc]

Re: 4.3L OMC will not run WOT

I don't know how the boat ran in the past. I bought it last summer. The outdrive is black with the cobra logo on it, but it's not original. The part that mounts to the transom is white.

 

[Don S]

Re: 4.3L OMC will not run WOT

The outdrive is black with the cobra logo on it, but it's not original. The part that mounts to the transom is white.

Time for some pictures.

 

[havasuboatman]

Re: 4.3L OMC will not run WOT

What is the diameter of the opening where the prop shaft comes out? Is it right about 4" or more like 4 1/2"?

 

[zeek7pc]

Re: 4.3L OMC will not run WOT

Here's a couple pics. I know it's ugly, but it doesn't leak....

 

[Don S]

Re: 4.3L OMC will not run WOT

First time I've seen a white Cobra transom shield, but it is Cobra. The drive is the standard dark charcoal gray and corrosion.

You are just going to have to check off all the things in the list after you actually check them.
Look at that tag on the drive just under the port trim cylinder. It should have the gear ratio on it. What is it?

 

[zeek7pc]

Re: 4.3L OMC will not run WOT

All the tag says is:

Model-985269
Eng-4.3L
Ser-TO588982

It didn't have a gear ration anywhere on it I could see.. You'll have to forgive me, I'm sterndrive stupid. All other boats I've owned have been outboards.