rusty intake ports on head ??

[Alumarine]

Hi there. Anyone know why just the last 2 intake ports would be rusty? I know it must be from water but why? 1974 mercruiser 140<br /><br />

<br /><br />thanks for the help

 

[Don S]

Re: rusty intake ports on head ??

Bad Manifold. You could pull the riser off, block off the water passages and pressure test the cooling passages and see if it leaks into the intake side.<br />Could also have leaky valves and pulling water from the exhaust back into the intake. How was it running?

 

[Alumarine]

Re: rusty intake ports on head ??

Thanks for the reply Don.<br />The riser is off and I'll pressure test it.<br />If it holds say 20lbs is that ok?<br /><br />To me it seems to be running not bad for a 30 year old motor but my brother says it doesn't have enough power to pull skiers, although that could be other issues.<br /><br />Compression is a bit low in the last 2 cylinders.<br /><br />Last spring when I put it back into service it had quite a bit of water in the oil. This spring no water in the oil although there was evidence of watery oil on 2 rockers and 2 head bolt cavities.

 

[Don S]

Re: rusty intake ports on head ??

Sounds like you need to do some serious repairs to get everything fixed all at the same time. Fixing one item and allowing another to be bad does't make things work together correctly.<br />15 or 20 pounds would be fine, but with bad compression, it could be just leaky valves allowing water to get sucked back into the cylinders.<br />Low compression could be because of leaky valves, or bad rings. or both, and leaky head gaskets isn't going to help either.

 

[Alumarine]

Re: rusty intake ports on head ??

Thanks again Don.<br />I'll check the manifold and riser to see if they are leaking.<br />I was going to give it a valve job and replace the rings. Also will check the cylinders for size, taper etc.<br />Then on to the crank and rod bearings.