Chasing a lean sneeze; 67 80HP V4

[Alan]

Hello to all;
With much help from this board, and some time and money, I seem to have my ’67 OMC 80 HP mostly figured out.

The last little concern before I hit the lake is a somewhat persistent lean sneeze.

I cleaned the carb most thoroughly, removing the welch plugs, and soaking it for days. New float adjusted carefully; needle and seat matched and recent. So, I’m investigating aspects other than the idle passages. Tightened up the packing nuts, (w/ newish, correct packing washers) and increased choking a bit. Starts fine, runs great at higher RPM.

My questions; is this motor more likely to engage in this non-preferred behavior in the barrel? And, are these motors just kinda sneezey when cold?

I don’t want to warm the motor all the way up in the barrel ’cause it warms the water up fairly quickly. Impeller is newish, and vernatherm tested as fine.

I read of others on the web who claimed that a few sneezes when cold are normal for these motors.

All opinions welcome, and many thanks to all for the tons of help!
Alan

[amuller]

There are a lot of things you really cannot properly check out in a barrel.

The obvious thought is that if it behaves when warm, but seems lean while warming up, increase the choking a bit by rotating the cover/thermostat a bit "tighter." This motor also uses an electric choke solenoid with the plunger working through springs, but I am not sure whether this acts to close or open the flaps. (On a car this would be an "unloader" or "pull off" and act to open the flaps against the thermostat spring pressure, but I don’t assume anything about OMC chokes….) Have you checked the calibration of that? Maybe somebody here can explain how to do that. If this is opening the choke flaps too far that could be the issue. I see that marineengine.com has cover/thermostat (379511) for $9.00. Maybe time to get out on the water?

[fleetwin]

It looks like the 67 80hps still used the thermostatic choke, with the very confusing electric choke "over ride". This crazy feature actually turns the choke off when the switch is engaged. These engines were designed/wired so the electric choke turns on everytime the key is turned to start, even when warm. So, engaging the choke over ride switch turns the choke off while cranking, to prevent flooding a warm engine. Someone may have disabled this feature, or changed the choke switch to reverse the feature. Yes, very confusing….
And yes, you can adjust the thermal choke warm up spring to help with warm up after cold starts. Like others have said already, trying to run one of these engines in a barrel shows little and creates confusion. I would definitely launch the boat in order to properly evaluate idle quality and cooling system operation…

[amuller]

I think OMC must have been choke-challenged, to have tried so many different designs. The manual I have explains how to assemble the choke I think you have, but not how it works or how to set it up correctly. Hopefully fleetwin or others with deep knowledge of these motors can point you to a source for that information.

[Alan]

All replies appreciated.
I’ve adjusted the bi-metal coil to increase choking a bit, and that seemed to help a little. I’ve worked with a lot of these on older cars and other motors, and like them fine. Especially when they’re adjusted correctly, and operating freely.
As for the electromagnetic choke, I disabled that years ago. Electric chokes can be irritating and intrusive. I usually manually choke it anyway.
I’ll take it out on the lake and post some pics of the results.
Many thanks to all;
Alan

[fleetwin]

Sounds like a good plan!

[Author]

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