83' Evinrude 175hp Overheating Issue

[Numlaar]

Hey all,

I have a 1983 Evinrude 175hp V-6 motor...

Ran into an overheating issue with it, and am looking for some advice....

It has a strong pee stream, but the stream is COLD.... water coming out at the lower unit is hot.

Ran it about 10 mins, and blew it up due to it getting extremely hot... (melted the coils to the heads and everything).

I thought maybe it was due to a cracked block, but don't see anything... Anyone have any suggestions on what may have been the cause? (Before I rebuild it, I want to be sure its corrected as to not blow it again). Luckily it didnt damage any pistons, so Im looking at a re-ring, and new gaskets if the block checks out.

Items to note:
1. Exhaust plate and both cylinder heads were extremely hot, the starboard side was worse than the port.
2. Motor had no thermostats in it (should have checked before I ran it, but didnt, my bad I know)
3. Severe corrosion buildup in both of the water jacket plates that go over the heads, and the bottoms were full of sand/salt, but not enough to plug it, the best I could tell

So any thoughts?

 

[Numlaar]

Re: 83' Evinrude 175hp Overheating Issue

I pulled the heads last night, and there was evidence of water in the middle and lower starboard side cylinders (the side that got hotter). Again I don't see any evidence of the block being cracked, so maybe blown head gasket?

Still have my original questions:

1. any idea what would cause the pee stream to remain cold, allow hot water out of the lower unit, but NOT allow water to circulate through the block?
2. Any idea how/why there would be water in those 2 cylinders, again when there is no evidence the block is cracked?
3. would a blown head gasket alllow it to overheat, but still have compression initially? (motor had 105psi dead on, in all 6 cylinders before i overheated it, now they are all over the board... ranging from 60 -90

Pistons and cylinder walls look great still, can even still see the cross hatching in the cylinder walls, so if the block continues to check out, im looking at a re-ring, and new gaskets... but I want to try and figure out why it was overheating when it was pumping... this one has me a bit stumped...

Thanks all!

 

[emdsapmgr]

Re: 83' Evinrude 175hp Overheating Issue

The telltale is plumbed into the back of the outer exhaust cover. The lower unit cooling water that enters the block, fills this exhaust area first. Probably why it's cold-it's right out of the lake. A strong stream indicates that the water pump impeller in the lower unit is working normally. That fact that you have a good telltale does not indicate that the block is not be overheating. Both heads and the thermostats are downstream of the telltale. If you have any internal issues (restrictions to water flow) to the heads/block/thermostats, the powhead can overheat. Some things to check: Crud/salt buildup inside the outer head covers is an indication that the water flow thru the head may be restricted. What you see there inside the heads is also inside the block. Pull the heads and inspect the water jackets around the cylinder sleeves. Make sure they are clear. There are 6 rubber water deflectors pushed into the block by each cylinder. These rubber hoses must be properly in place-their location is such that the water flow narrows there, and debris can accumulate and cause a single cylinder to overheat. If you find a lot of salt and crud internal to the block, you may want to pull the water cover off the top of the block (under the flywheel) and have a look inside (between the two cyl banks) for debris buildup. Water inside the cylinders can come from two sources: a bad head gasket or a leaky exhaust cover gasket. With your compression numbers, sounds like your head gaskets were ok. When you pull the exhaust cover off, check it for clear water passages also. Leaky exhaust covers tend to leak water into the bottom (lower) cylinders on the block. The big thing to resolve is why the hot horn inside the control box did not go off. Both heads on that engine have switches for overheat protection. When the head temp gets to 212 degrees, they will short to ground and turn on the warning horn in the control box. When you have time, pull the lead off both cyl head temp switches and touch them to ground when the key is on. You should get a horn when testing each head switch lead. You should be running a pair factory thermostats in the engine.