'89 OMC's bogging a full throttle

[Liquid_force]

Hi, the old OMC has come out of the gate a little sluggish this season.
After replacing fuel fill and vent hoses, the clogged/corroded check valve on the fuel supply line (deleting it actually), some starter work, and a new thermostat gasket and o-ring we finally got it out and running.

It starts and runs fine for casual cruising.
However, when you nail it from a stand still (such as pulling out a skier) it bogs -- not immediately though. It gets to the point right before it wants to plane out and just struggles. If I back it off 1/4 throttle or so, then go again it comes out of it.
It has been known to have a stumbling problem, but that always shows up the instant the throttle goes down.

Initially I'm wondering if it's not just a low voltage (weak spark) issue because another problem it has is when underway (say at 25mph for instance - maybe 3k rpm) and you try to adjust the trim that bogs the motor as well.
It seems to me that when that fuel/air is really being dumped in there's just not enough fire to get a full combustion...I don't know...I'm just thinking out loud.

Any ideas?

 

[danond]

Re: '89 OMC's bogging a full throttle

Fuel filter/water separator replaced this year?

 

[Liquid_force]

Re: '89 OMC's bogging a full throttle

Fuel filter/water separator replaced this year?

It was replaced halfway through last year. It probably doesn't have 20 hrs of use on it, closer to 10 if I had to guess.

 

[Wet Wonder]

Re: '89 OMC's bogging a full throttle

Check the distributor. Timing may not be advancing so spark is hitting the piston late at high rpms.

 

[danond]

Re: '89 OMC's bogging a full throttle

It's times like these where I just go through and get it all done. Rebuild the carb, replace the points, replace the plugs, check out the wires, replace the cap, etc.

Boats seem to need all that crap more often than cars, and with your crappy/dirty fuel issues, it wouldn't surprise me if something made its way into the carb and plugged or restricted a fuel circuit.

If it cruises fine I wouldn't start with spark, though timing could be an issue. You can rule that in or out in 10 minutes with a timing light.

 

[P 0 P E Y E]

Re: '89 OMC's bogging a full throttle

Boat was running great before, now there is a problem.

You as the captain are right on. Something is now different.

I would first check the fuel water separator for any signs of water or contamination. By Check I mean purchase a new element in stall the new filter per specs, and inspect the contents of the old one by dumping it upside down in a suitable container and look for the salad dressing.

If there is no problem there, I would suggest you triple check all the work you did. There just might be a correlation.

Then I would inspect the vacuum (if equipped) advance for the distributor timing. See if it causes the plate in the distributor to move when you apply some suction to the hose with your mouth. If you hold your tung on the hose, the plate should stay in one position.

Check the spark plugs one more time, take a look under the cap for rotor problems, change the condenser if it is not new.

I would also inspect the accelerator pump for proper operation.

Try to take your time and not jump to any optimistic conclusions while trouble shooting. Perform tests and check the results.

Hope you are able to find that elusive gremlin. Good luck and keep your chin up.