Timing ? Boat won't plane 1968 merc 500

[rogueflyfisher]

16 foot fiberglass boat with Merc 500 - 50hp. Boat doesn't get enough power wide open to get on plane. Runs great at idle, and slow trolling and medium speeds.<br /><br />A couple of notes: the engine won't shut off until you hold the choke down after shutting off the key.<br /><br />Also, when you take the spark plugs out after running, the plugs are a little gunked up with oil.<br /><br />Also, it's not the fuel pump, since when you pump the bulb it doesn't increase the speed at all.<br /><br />Does this sound like a timing problem ? Or something else?

 

[joblo33]

Re: Timing ? Boat won't plane 1968 merc 500

Check for spark in every cylinder. Also check compression. The key stop not working could be caused by a number of things. There could be a bent pin or dirty contact where the controller wire connects to the engine. The orange wire could be disconnected from the black box. The ignition switch could be faulty/corroded. The oil on the plugs could be from a lack of spark or intermittent spark, or maybe a rich mixture.<br />Eric

 

[andy6374]

Re: Timing ? Boat won't plane 1968 merc 500

I had similar problems with my 88' V6 200hp merc, i.e. the engine bogging down at WOT, but idled fine. I took off the carbs, gave them a good soak in some carb cleaner, new gaskets and now she runs great. To clean out all the gunk in your cylinders, get a can of power tune or seafoam to decarb.

 

[Laddies]

Re: Timing ? Boat won't plane 1968 merc 500

First is the engine ign. magneto or CD they were available both ways in 68, alot of the magneto engine wind up with CD plugs in them and run about like you discribe