2.5l mercury overheating

**Aaronhl** · 05-06-2024, 12:53 PM

Is there a way to test the coils without running the engine?? Or without more than 2 hands/ at home not in the water

**Aaronhl** · 05-08-2024, 09:20 PM

I had an overheat issue and the piston looks very similar to yours with a "halo" in the middle of the piston. I've worked on a few dentonated pistons are they dont typically have the "halo", they usually have more damage than this...

Is it true a bad key ignition switch can cause firing issues and maybe end up overheating?

**LakeFever** · 05-09-2024, 02:04 AM

Yes the black/yellow wire has to be open and clean when running. If there is any ground present when the key is in the run position the switch is faulty. Causes issues with the stator iirc

**markmc60** · 07-08-2024, 04:04 PM

I am fighting a 2.5 over heat as well, watched your youtube vids, can you explain the coil test that the tech suggested to isolate a bad coil? as much info as possible. this 2.5 is a stock but I swear it has the double fire.

Originally Posted by Smalltownbassin

What a freaking ride! Sad thing is.....im still not sure its fixed. Picking up where i left off, new set of SBs toasted immediately, then another set, and another, and another. Somewhere between one of those another's' i installed a new trigger & stator. Same double fire. All 6 coils are sparking on time but also showing other holes. Called CDI. Spoke to a knowledgeable tech who suggested a specific type of coil test. Turns out i had a bad coil on #4 & #2. Put a new set of coils and ignition wires on. Seemed fine on muffs but overheated on the water. Got it home and found the new coil wire on #2 was OL. I figured since #2 was likely not firing, #4 was reaching overheat temp before the stat opened. Got that squared away and its doubling down again! One more set of SBs, flywheel, stator & voltage regulator later, its firing normally! Woohoo! But the SOB still got up to almost 170 on muffs pretty quick. Wind up taking a carbide burr to the LWP holes and almost doubling their diameter while also dropping separate stat dump hoses out the heads instead of the usual bridge with a single dump. Down to 150 now on muffs. Gonna water test this weekend. Just in case...anyone wanna buy a boat? LOL jk

**powerabout** · 08-06-2024, 01:40 AM

Are we checking the water diverters in these overheated engines?

**tlwjkw** · 08-06-2024, 03:24 AM

Originally Posted by powerabout

Are we checking the water diverters in these overheated engines?

don't think production motors have 'em..........

**powerabout** · 08-06-2024, 04:52 AM

Originally Posted by tlwjkw

don't think production motors have 'em..........

When stock cooling systems on 2 piece adapters.

**powerabout** · 08-06-2024, 04:52 AM

Originally Posted by tlwjkw

don't think production motors have 'em..........

With stock cooling systems on 2 piece adapters, what do we have here?

**tlwjkw** · 08-06-2024, 05:42 AM

diverters only came on high performance stuff.. not any production motors... they have gotten popular with motor builders as an addition on all tha V6's though....