2.4/200 starts and idles like a dream but gets too hot on the muffs

[pcrussell50]

This is a big head scratcher to me... After finally de-salting and cleaning this 2.4/200 I bought last summer, I finally go around to firing up on the muffs an hour or so ago. I got it before it was too late. Everything came out without breaking. Corrosion was starting but had not gotten far.

It took way too long to for water to start coming out the tell tale hose, and it was too hot, and too weak. Scalding hot in fact. I think it was boiling because of steam. For some reason it did not set off the overheat buzzer, which I then tested by grounding it, and it works perfectly.

I'm at a bit of a loss here...

-I got the exact same results bot WITH and WITHOUT thermostats
-the thermostats are used but test fine in a pan of water (but again, even without thermostats, the problem was identical)
-Compression is 120 even on all six
-cranking max timing was spot on when I got it and I confirmed it at 22 BTDC
-idle timing is per manual, at 7 deg ATDC
-with link and sync and WOT and timing set per the manual it idles nicely on the muffs at 700 rpm.
-starts easily, and idles as long as you like (just weak telltale and scalding hot water
-buzzer does not go off, and tests as functional
-The block is one of the last 2.4/200's a late November 1990 build stamp, and the heads are the newer, one-piece style. I

Just left my shop to get my leak down tester.

-So, weak telltale that takes to long to start, and the water is way too hot, scalding, and steam almost like it's boiling

-If something is cracked and allowing combustion gases into the water, is it more likely a head, or the block?

Any ideas before I head back and to the leak down test?

-Peter

[pcrussell50]

[SOLVED]

Leak down test was healthy 94-97@100 psi.

So I took the heads off… And voila. Multiple salt/corrosion blockages. In the raised casting area on either side of the head. Cleaning them up right now.

-Peter

[Jim Speros]

You cannot troubleshoot an overheating problem effectively on muffs.

[pcrussell50]

You cannot troubleshoot an overheating problem effectively on muffs.

Oh Jim, Just so we’re clear, I did not put it on the muffs to diagnose an overheating problem. this motor was new to me. I had never run it before. So I did not know I had an overheating problem UNTIL I put it on the muffs.

Also, BEFORE I put it on the muffs I tested the sensor, buzzer and the thermostats BEFORE firing it up for the first time.

I only knew it was hot because the telltale was slow to form, and weak and too hot. The buzzer never went off. I just know the telltale water was way too hot from experience.

So, after I discovered it was too hot on the muffs, THAT is when:

- I did a leak down to look for a cracked head… and when that turned out normal,
- I pulled the heads and that’s where I found the salt dams. They were pretty soft. Crumbled away easily.

Would you have done something differently?

-Peter

[Jim Speros]

The very very first thing n any new to you engine IMO is water pump gearcase service.

Did I miss where you said you changed water pump? I looked over before typing this.

1 Replace water pump. 2 Does it pump water on muffs, 3 Ramp test.

[pcrussell50]

The very very first thing n any new to you engine IMO is water pump gearcase service.

Did I miss where you said you changed water pump? I looked over before typing this.

1 Replace water pump. 2 Does it pump water on muffs, 3 Ramp test.

The overheating powerhead was put onto a mid with a known-good water pump that was working well on a different motor, (a 2.0/150). If I hadn’t discovered the salt dams in the heads, I was going to look at the water pump, even though it had just been working nicely. In fact, now that the salt dams are cleared, even though I don’t expect the low flow problems to persist, if they do, I will go to the water pump next.

Got a few other things to do before I scrape the gasket surfaces and put the heads back on with new gaskets. The salt dams came out easy enough with a little vinegar.

===

I hope I’m not coming off as an a-hole. You are one of the legends here and I read your posts and learn and value your input. I’m quite sure you have forgotten more than I’ll ever know about this stuff.

-Peter

[Jim Speros]

Hey Peter, Its all good. I'm just offering info where I can. I am sorry I can't keep up with all the side stories like you mentioned with the powerhead swap.

[25two.stroke]

You cannot troubleshoot an overheating problem effectively on muffs.

LOL
You and I both know we do this daily.

[random customer] "If my motor starts up and doesn't pee on the flushers do I have a problem? If I rev it up to 2000 it starts to pee so the water pump must be good, right?"

Your post #5 kinda clarified what you meant to say. You can't troubleshoot problematic overheating issues on the flushers. You can diagnose MOST overheating problems on flushers with both inboards and outboards...but only when its major and blatant issues. Like you implied, a slightly failing water pump will work just fine when you are feeding it 25psi of water pressure, but as soon as you put it in the lake and make it suck it can't.

Peter what you said in your first post word for word describes a bad poppet valve. Or a poppet with a piece of wood/junk stuck in it. Interesting thing to consider for me and anyone else reading this. I woulda said poppet for sure and it turned out it wasn't!

[pcrussell50]

Peter what you said in your first post word for word describes a bad poppet valve. Or a poppet with a piece of wood/junk stuck in it. Interesting thing to consider for me and anyone else reading this. I woulda said poppet for sure and it turned out it wasn't!

Well, in the spirit of thorough investigation, it might still be the poppet. I won’t know until I have scraped the old gasket material, put the heads back on and tested again.

Prior to running it yesterday and discovering the too hot and too weak telltale, I had rebuilt the poppet with a fresh diaphragm because I was getting leaking from the vent hole, when I flow tested the block by pushing a garden hose into the copper pickup tube (no lower unit, thermostat covers off). Water gushed out the open thermostat covers AND out the open, water pressure fitting on the top of the block behind the flywheel. Not sure if that is and adequate diagnostic for the poppet. But it’s in clean with no obstructions and no leaks, now that I replaced the diaphragm.

-Peter