1988 Mercury 135 Sluggish during warm-up

[bikker2001]

I have a 1988 Mercury 135 HP that is sluggish for several minutes during initial warm-up. The motor was purchased new by my Dad and is still mated to it's original 19 foot Sea Ray Seville Bow Rider. This problem has existed for the past 3 years.

Here's the details. The boat always starts just fine and idles fine. Once out of the marina after the boat has warmed up and you give it full throttle it will not plane off. It runs, but not fast. After a while you can hear what seems like another cylinder start to come on line and the boat will finally get up on plane and run about 32 MPH. After a few minutes like that it will finally kick in completely and run good and strong 46 or so MPH. It seems that shutting the engine off and then restarting and revving in neutral seems to help. Once the boat warms up and runs good it runs good all day.

I had the boat at the lake this summer for 7 days and after 2 days the problem went away and ran great the rest of the week. But after I got home and the boat sat for a week I encountered the same problem.

What I've done: Plugs were new last year (and I've pulled them and they look good), I've run a carb cleaner through almost all tanks this summer, replaced the fuel filter, by my math the automatic oiler is dispensing the right amount of oil. I'm running Shell premium gas. (no ethanol)

Any thoughts would be appreciated.

 

[Chris1956]

Re: 1988 Mercury 135 Sluggish during warm-up

Lets go on the premise that some of the spark plugs are fouling for a while. I would check the enrichener (choke) solenoid to make sure it is not stuck open.

Also, you may have a slight leak in the fuel pump diaghram. Perhaps a rebuild of the fuel pump will help.

 

[bikker2001]

Re: 1988 Mercury 135 Sluggish during warm-up

Thanks Chris. I think I can handle the pump rebuild which I will try this weekend. But how do I go about checking the enrichener solenoid?

 

[j_martin]

Re: 1988 Mercury 135 Sluggish during warm-up

If you would take the cowl off and check the stator voltages with a DVA right after a cold start, you might find that it is failing when cold.

I'm thinking moisture causing high voltage to fail. Maybe coils or spark plug wires. Try starting it with the cowls off on a cool moist night and look for fireworks.

If you started it and fooled around a little at part throttle, quitting before it starts to straighten out, then pull the plugs, the dark plugs would be the failing cylinder(s)

These are tough. You have to sneak up on em.

hope it helps
John