Merc overheating issue please help

[LakeFever]

What temp is considered the shut it down danger zone?

[OnPad]

My opinion for 60-70 degree water. At idle, or low speed 175 degrees is getting warm. At speed, more than 150 degrees, something is probably wrong. If the horn goes off at idle, you need to reevaluate your life. If it goes off at redline, it's probably too late.

[Aaronhl]

Ok so maybe the temp is ok then I will continue watching it, engine seemed to run better in and out of idle with idle timing screw set at 3 BEFORE maybe that’s ok since I don’t have the idle advance module ??? Manual says 2-9. After but no way I can get anywhere near 9 as the screw bottoms out

[OnPad]

With the boxes removed you can take Mercs timing recommendations and throw em out the window. My engines end up with the center of the trigger barrel almost splitting the case seam. I don't know if I even checked where that ended up being on the timing light, but it's likely a little btdc.

[skialot2]

All my V6 Mercs temps run about like yours. They run about 170 in the 5 mph zones. and about 140 at speed. It is normal for the water tube to come out of the adaptor plate. Just push back in. It uses the exact same grommet as the water pump.

Your overheat alarm on the original powerhead probably went off only because you melted a piston. You didn't melt 1 piston because you overheated. You would have melted all the pistons not just one.

[pcrussell50]

Aaron, keep us posted with a few more updates until you feel your issues are resolved.


Not experiencing overheats myself (ordinary carb 2.4/200), but the stories are scary and the more we learn from reading other's stories, the better for all of us.

-Peter

[Aaronhl]

Thanks for the reassurances - sounds like the engines temp movement is somewhere it needs to be

Was able to get a good rip with the boat today - This is with the idle speed BEFORE TDC - and overall the engine ran very well. It was cold today had to high idle a lot, but even in gear for a while the temps did not rise. I think the idle speed/timing adjustment was helpful in normalizing the temps around idle and slower speeds. The engine was running no more than 150 degrees at high speed and slow speeds

One thing I do notice is that when engine trimmed up and going a few mph the engine shakes, seems like more than my other 200 does on my other boat...I am wondering if the fuel pump has something to do with that, my other boat has an electric pump...

All six *NEW* spark plugs were wet and brown

here are some quick pictures, notice the idle speed timing screw is in the center..I forgot to take a pic of the little arm but it does split the gear case like posted above...I could only get the high speed timing to max at 22 degrees (I know thats pretty much all I need) but I am wondering why the arm does not go further, maybe because it's not a mec oem trigger...?

Also last night I changed where the 8 pin harness is grounded, the previous owner had the black wire grounded to the hex screw on the bottom of the starter solenoid, so I moved it to the phillips set screw immediately to the right-forward of that on the mounting plate, not sure if that had anything to do with anything maybe intermittent spark or something like that...

[Tagg]

I've had this issue with my 2.4 200 and my 2.5 175. I run through a few no wake zones where I fish and they both will push 170-180but only at low speed. When I replace the water pump, I get about 3 trips where they run 140-150, then it'll start creeping up again. I usually just pop it in neutral and run the rpms up until the poppet opens and it the cools right down and I carry on. It's irritating but I'm not going to replace the pump every 3rd trip. Been living with it for 20 years. Wish I had a better answer for you.

[skialot2]

Adjust the trigger link rod shorter to get more timing. Doesn't matter if it sits on the split in the case. Motor probably shakes more because the mounts are softer. Spark plugs look great.