Very wet plugs on Merc 150hp Blackmax

[LaGaviota]

I have been trying to get this '82 Blackmax working for 2 years. It boggs down at wot. I have replaced most of the electrical components and my "master merc mechanic" can't find any problems with the electrical system. The carbs have been cleaned and floats set by the mechanic. The plugs get very wet with dark oil after just seconds of running. I can clean them off and then run fast before it boggs on me again. What is my problem? Could it be the reed valves?

 

[Barnacle_Bill]

Re: Very wet plugs on Merc 150hp Blackmax

Are you using fresh fuel mixed 50:1? Were new needle and seats along with new gaskets installed in the carbs and were they cleaned properly. Fuel pump rebuilt? How's the compression?

 

[j_martin]

Re: Very wet plugs on Merc 150hp Blackmax

Are you using fresh fuel mixed 50:1? Were new needle and seats along with new gaskets installed in the carbs and were they cleaned properly. Fuel pump rebuilt? How's the compression?

At WOT the reed valves stand wide open. If you could magically remove them at that time, it wouldn't make any difference to the engine.

Clue is the oiliness. If it runs strong, you may have mixed your fuel wrong, or the VRO could be malfunctioning, overoiling the fuel.

If it isn't running strong it could be an ignition problem. Doesn't sound like that, though.

The other problem is that the carbs might have been messed with. They might even not be the original carbs. If you can get all the numbers off one carb, we can check it out. Carb jetting goes with the carbs more than with the motor, thus if you change to a different carb, you leave the jets alone untill you determine if the mix is off. It usually won't be much. To add to the problems, some carbs have been messed with trying to run ethanol, then dumped on the market at eBay.

A remote possibility, though it usually really trashes the idle, is bleed line check valves and lines (and routing)

hope it helps
John

 

[hkeiner]

Re: Very wet plugs on Merc 150hp Blackmax

The plugs get very wet with dark oil after just seconds of running.

If you indicate whether your motor has oil injection or if you mix the oil yourself with the fuel, it will probably narrow down the suggestions your recieve to those that are most relevent.

If the motor has oil injection, the first thing I would check is whether the crankcase check valve that supplies air pressure to the remote oil tank is OK. If it provides too much pressure while the motor is running or if it does not relieve the pressure after the motor is shut down it can cause too much oil to be mixed with the fuel going to the carbs. Also, if the check valve between the oil pump and the fuel pump is stuck open, it will allow oil to siphon into the fuel line while the motor is off causing too much oil to be mixed with the fuel going to the carbs. Replacing these two check valves might solve your problem. Of course, if you do not have oil injection on your motor, never mind.

 

[LaGaviota]

Re: Very wet plugs on Merc 150hp Blackmax

thanks, guys for the good input. i have a premix fuel and it is definitely a fresh 50:1 mix. The carbs have been professionally rebuilt, but this problem occurred both prior and after the carb work. Teh electrical system was checked out and was ruled out. The merc master mechanic that did all of this work said that he thinks that it might be the reed valves, but he says that it is rare and it is a labor intensive job. The engine starts and runs at low rpm so nicely, that I hate to give up on her. i'm thinking about either tackling the reed valves myself or buying a new engine (don't have much money) or selling this nice 20ft whaler and trailer and calling it quits. what would you do?

 

[j_martin]

Re: Very wet plugs on Merc 150hp Blackmax

Like we said, if it idles good, the reed valves are good. They do not have any effect at WOT as they are standing wide open.

This does not compute. Something is not as it should be, or it would run.

Either the tech is missing something, or some parts are not original or compatible.

hope it helps
John

 

[LaGaviota]

Re: Very wet plugs on Merc 150hp Blackmax

ok, thanks John. I'm going to start looking for a decent used 4 stroke outboard to replace this merc. thanks for the help.