40hp Big Twin Lacks power

[aziegner]

Model Number Is: 40552m
Having power issues. New gas, replaced plugs last year and fuel lines.
Not sure how to:
1. Clean carb
2. Adjust lean screw
Any advice where to start?
Zigfamily23@yahoo.com
NEWFANE, VT

[david-bartlett]

The best way to clean the carb is to remove it from the motor. Not a complicated job on this motor. Only low speed needle is adjustable, high speed is fixed. Get a kit from the dealer and open it up.

Are you sure it is fuel related and not ignition. Are the coils original, or have they been replaced? Points and plugs clean?

[raglover]

Carb kit may be a good thing if you have never done it, but also may only be running on one cylinders Nader, among a couple other things.

Check for spark first, it is free. If you have it on both move to carb/synchronizing carb and mag plate

[frankr]

Personally, In my opinion, since it is much easier to remove the carburetor with the electric starter out of the way, and it is easier to remove the electric starter with the flywheel out of the way, I would do both at the same time—ignition and carburetor. Besides, the problem is more likely to be ignition than carburetor anyway. Likely is running on one cylinder.

So, the easy routine is:
Check compression first to make sure you have something worh messing with.
Remove recoil starter and flywheel
Remove Electric starter (and generator if it happens to have one)
Remove carburetor.

You will need a puller to get the flywheel off and a torque wrench to put it back on at 100-105 ft/lbs.

[1946zephyr]

I would check the ignition system first, before opening up the carb. It sounds like you’re running on one cylinder.
Those carbs are pretty bullet proof and have rarely given me any trouble, but original coils are usually the issues.

[crosbyman]

compression figures ok ??

Joining AOMCI has priviledges 🙂

[jerry-ahrens]

When I buy about any old outboard, I don’t even try to start it untill I go through everything, carb, new points and condensers and an impeller. On the 50’s and up OMC’s they get a carb kit, an OMC tune up kit that comes with good quality points and condensers, a water pump impeller, and lastly I replace the shift rod o ring [seal] weather it needs it or not. This may be an overkill, but I rarely have an engine that doesn’t run great after all these area’s are serviced. That doesn’t mean I’m a super mechanic, I just want it to run and not break down on the lake. I’ve never followed the old saying, ”if it aint broke don’t fix it”.

[wiscoboater]

On a motor like that am I the only one that thinks "cleaning" a carb is a waste of time? To clean a carb properly you have to remove and disassemble it so why would you not put the new rebuild kit in. Your 98% there anyway.

[chinewalker]

If it runs, but doesn’t have power, it’s likely ignition issue. Carb issues either show up as hard starting or poor running. They generally don’t run well, but lack power if it’s a carb issue.

[edgartc]

Make sure the remote cable is adjusted so the gear shift is far enough to let the neutral stop is clear to allow the throttle to move to WOT

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