Not Stator! Could this be a defective Trigger?

[fisher11]

Here goes: I have a 115HP year 2000 Merc. When it's cool outside, everything is fine. But once the motor sits under the hot sun, say 75 degrees or higher, it runs like hell.<br /><br />It always starts fine but when I power-up under load, the motor will run for a few minutes then misses, runs real rough, and eventually quits. It always restarts. The hotter the sun, the worse it is. (When it's not so hot, it won't fail until high RPMs, when it's a very hot sun, it will fail at much lower RPM but never goes solid-- it always restarts and idles.)<br /><br />They haven't been able to reproduce it in the tank. I think this owes itself to the need for heat build up under the cowl and the fact that it seems to fail under load.)<br /><br />Three times I've taken to the shop with no success. I've tried different plugs. I had them replace the stator. I've tried electronic part "cold spray" on the four CDM's and the<br />voltage regultor. No change. Would the trigger be a likely candidate for the offending part?

 

[Kenny Bush]

Re: Not Stator! Could this be a defective Trigger?

interesting problem. Your symptoms seem like a coil is dropping. Coils usually start going as they heat up. Basically the wire in the coil is broke and when it heats up, it expands and eventually pulls wires apart. I personally have never had a trigger plate do that. I would test each coil while the engine is running in this bad condition. Once engine heats up and starts acting funny, leave it running and then pull one plug wire off at a time. If the coils are working properly, you will hear a RPM drop. If you here no change in engine RPM, then you found the bad coil. Hope this works for you.

 

[fisher11]

Re: Not Stator! Could this be a defective Trigger?

Thank you for the recommendation BushCat!<br /><br />Are the coils you reference part of trigger or are they actually the part known as a CDM? (My motor diagram shows each plug wire connected to one of the four CDM's.)<br /><br />Also, is it possible this could be a plug wire breaking down?<br /><br />There are about 14 electronic parts that I figure have a chance to be the culprit. Any of these that we haven't talked about have a reasonable chance of causing this in your opinion?<br /><br />Spark Plugs (4) - (not it: swapped out)<br />Stator - (not it: already replaced it)<br />Trigger <br />CDM (4)<br />Temperature Sender<br />Thermostat<br />Rev Limiter<br />Voltage Regulator

 

[andrewkafp]

Re: Not Stator! Could this be a defective Trigger?

You can test the trigger with a multi-meter, but I had a corroded wire on my trigger (Cyl no 1 -<br />4cyl 50 merc) and it ran very badly, and backfired under load. I would test all the wires individually and this will isolate the trigger as a problem. Before you go out and spend $$$ on a new one to find it aint the problem

 

[fisher11]

Re: Not Stator! Could this be a defective Trigger?

If the failure was solid, then ohming the trigger would be simplier. Unfortunately, the motor only wants to fail intermittently. I believe the Merc mechanics tested the trigger and found it to be good (... but then, the motor was running fine in their tanks).<br /><br />Parts express shows the trigger is about $75. I hate to throw money at this needlessly but this is the third summer now where I've had curtail boat trips due to this problem.

 

[clanton]

Re: Not Stator! Could this be a defective Trigger?

Try www.Rapair.com, I think they were the maker of this system. They may help you trouble shoot the system. It is inportant that all connections and grounds are clean and tight. You could try heating the ignition parts one part at a time with hair dryer. The CDMs are grounded thru each other CDM then thru engine harness. About 6/10 pages in manual on this system, and rev limited not used on all systems.

 

[fisher11]

Re: Not Stator! Could this be a defective Trigger?

Thank you Clanton. <br /><br />The idea to [carefully] heat ignition parts is a great idea however I cannot do much to get the failure to occur out of the water. It seems to require higher RPM's and a load-- something I can't see trying in my backyard with only muffs on the motor. <br /><br />Also, the trigger is down below the flywheel where I cannot do much to alter it's thermals.<br /><br />Alternately, I was able to apply "freeze-spray" to the parts I could easily reach. I sprayed the voltage regulator and CDM's when they were under a fail condition while on the water. The freeze didn't seem to change anything as the failure continued to occur. Accordingly, I sort of reduced the likely cause of the problem to these:<br /><br />Trigger (cannot reach)<br />Plug wires (didn't try to spray them)<br />Temperature sender <br />Thermostat<br />Rev Limiter<br /><br />I haven't talked about fuel but this feels like an electronic condition.