Mercrusier 3.0, 140 Help

[EClass20]

I have been on this forum for the past few weeks and have found it very useful. But now need some help as I am stumped.

I bought a 1985 Chris Craft a few weeks ago and it was not running good at all and stalled with a load. I fixed it to where it got to around 3000rpm and 29-31mph but no more. Now it won't even get there.

Runs fine idle with some accel. up to 2000, hesitates then kicks up to 2500-2700 but thats it. Even @ WOT.

List of what I have done:

Running 93o gas and added Seafoam.
Replaced plugs with MR43T
Replaced / Upgraded wires.
Original coil tested fine.
New points / distrib.
Set Dwell to 28d
Timing was way off but is spot on now.
Compression 120, 125, 125, 130 dry and wet.
Fuel pressure good on gauge.
Cleaned / rebuilt Carb. with kit. including accelerator pump. Changed fuel strainer. All gaskets. All pins and needles! Set choke 1 mark rich per manual.
Changed fuel pump filter.
New oil and filter.
Water pump gasket. (Had small leak)
Valve Cover gasket. (Had small leak)
Rocker cover gasket. (Had small leak)
Tightened exhaust clamps. (Had small water leak)

I Still have small oil leak behind timing gear but figure it is the oil pan gasket. Not a bad leak so I haven't worried about it yet.

Thought it maybe fuel starved and messed with carb. needle but it didn't change a thing.

What else can I do or check? Thanks guys.
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Engine Won't Reach Operating RPM. Check

1. Fuel condition. Type and Octane possibly old fuel <----Done
2. Propeller pitch or diameter, damaged blades <----Looking into to see if correct
3. Restricted fuel pickup tube or anti siphon valve Fuel System Test <----Haven't checked but pressure OK?
4. Crankcase oil volume, high oil level can cause aerated oil and lifter collapse <----4 quarts per manual
5. Marine growth on hull and outdrive <----Baby bottom clean
6. Wrong gear ratio in outdrive <----Haven't checked
7. Restricted carburetor air intake (clogged flame arrestor) <----Clean and rebuilt
8. Restricted exhaust system (broken exhaust shutters/flappers) in engine transom shield or drive <----How to check?
9. Poor cylinder compression Compression Test <----Good
10. Carburetor defective, or wrong type. <----Good
11. Fuel pump pressure and vacuum <----Good
12. Boat overloaded, improperly loaded, or improperly trimmed. <----Good
13. Engine Overheating <----Good
14. Engine timing and ignition system operation <----Spot on
15. Remote control cables and linkage for proper travel to open throttle plates fully. <----Seem OK but am checking again

 

[zbnutcase]

Re: Mercrusier 3.0, 140 Help

Have you checked the mechanical advance operation?

 

[EClass20]

Re: Mercrusier 3.0, 140 Help

Have you checked the mechanical advance operation?

I haven't. How do I check it.

 

[TrybalRage]

Re: Mercrusier 3.0, 140 Help

You say you have fresh fuel, how much is fresh? Do you have old fuel mixed in? Do you have a fuel/water separator filter?

 

[EClass20]

Re: Mercrusier 3.0, 140 Help

You say you have fresh fuel, how much is fresh? Do you have old fuel mixed in? Do you have a fuel/water separator filter?

I drained out old gas, cleaned tank. Put in 18 gal. new 93 oct. Added almost 1 full can of Seafoam. Full can treated 24 gal so I didn't use all of it. I do not have a water / fuel separator.

 

[NHGuy]

Re: Mercrusier 3.0, 140 Help

You sound like you "get it" so I am probably telling you stuff you know. But here are my thoughts.
Pull the fuel filter & check for obstructions, if you find anything replace the filter, then remove all your fuel and filter it til it's perfect. Or save it for the lawnmower. Also remove the sending unit and make sure the tank is pristine inside. It really has to be perfectly clean.
Remove and clean or replace the anti siphon valve. It's cheap enough.
Check that the vent is clear. Check that the fuel line isn't holed somewhere. A hole or crack can allow air where you want fuel.
The remote fuel water separator fixture costs about $40 or $50, I am glad my boat has one. Changing the filter is a quick spin on like a canister oil filter on a car.
You check the exhaust by removing the rubber section behind the riser and look down the pipe with a light. If you see no flapper in there it may be lodged down by the outlet to the through prop exhaust. You might be able to apply some backward air pressure through the prop hub cavity and blow free some stuck stuff. But if you have to remove the exhaust bellows don't worry, it's more important to have unobstructed exhaust. A bellows is an expendable at this point.
I think though, that you want to get a driver and a timing light to check where the timing is when the trouble occurs. Do it on smooth water and BE CAREFUL not to get tangled up in the belts. If I knew the procedure to check your advance I'd tell you, but I am not versed in your ignition system. Someone on here will know the advance curve for your motor. But if no one does, suffice it to say that you should be well into the advance by that 2000 rpm problem point.
I'd run 89 octane fuel, I believe that matches the compression ratio you have. And if they don't have marine fuel without ethanol where you boat, get some Startron or other marine fuel treatment to keep the ethanol from combining with moisture in the fuel. Ethanol and water = trouble.
Pull & inspect your spark plugs & tell us how they look now after the poor running, they could give a good clue.

Good luck, you have to be just about there.