Mercruiser 165 rust in intake

[rozicrc]

Hello,
I picked up a 165 to rebuild for fun with my boy as well as to spare the one in our boat. When I picked it up it has 140 compression on all cylinders, milky oil, but ran. When I broke it down with him, we found rust in all the cylinders, heavy rust on the intake and head (not a typo), clean exhaust side, and no evidence of a blown head gasket. Camshaft was shot and had evidence of leakage past the seals and a plugged weep hole. Block and head have magnafluxed ok, but head needs a lot of work on intake side. Cylinders cleaned up with 0.020" oversized. What would cause water or coolant in the intake and cylinders other than being left outside in the rain? I can think of many thinks on the exhaust, but those valves and passages look new.

I have double heckled the riser and exhaust and they are good. Any ideas on this?

 

[Bondo]

What would cause water or coolant in the intake and cylinders other than being left outside in the rain?

Ayuh,..... I think ya answered yer own question,.....

Runnin' it is probably what wiped out the cam,....

Surprised at the compression number,....

 

[stonyloam]

The plugged weep hole is the culprit for the cam (and probably bearings). The weep hole drains the space between the seals. With the weep hole plugged coolant that leaked past the front seal was forced past the second seal into the crankcase, rather than than harmlessly dripping out into the bilge. The antifreeze oil mix will quickly trash the cam surfaces and bearings. Sometime a bad exhaust elbow gasket will allow water into the cylinders. Were any of the cylinder head chambers pitted? Good luck with the rebuild!

 

[rozicrc]

I am with you, cylinders were not pitted and exhaust was sooty with no rust. It did not come from the exhaust end. And the intake passages on the head being so bad threw me as I have not seen that before. I just pressure checked the intake and it tested good...

The camshaft I know was leaking as the coolant system would not hold pressure and the camshaft with the pan removed showed rust on the oil side of the seals. I am at a loss on how corrosedthe head was on he intake. Rust was worst on numbers three and four. The more I think about this the more I think it was outside without the flame arrestor on

 

[stonyloam]

Yeah, sounds like it was exposed to weather with the valves open.