Rusty valve stems, what do I do next?

[herring627]

See pics...how bad is it? What if I continue to run it? What would you do?

Back story: Boat was running well until it overheated. Did not know anything about boats then after a $500 Sea Tow I started to wise up. Impeller was completely shredded, (only bits were found!), this and the thermostat were replaced. Took the boat out and warning buzzer went off after 5 min. (this time I had enough since to kill the engine and bring it back in under cooler temperatures). Have yet to pressure test it, maybe a leak? Notice a lot of rust buildup around the manifold. Took that part off...oh oh, rusted walls and surfaces ... replaced manifold and now...these valve stem thingings - not good, not good at all. I think I may be over my head, but then again, what is there to loose if the damage has been done?

This is a Volvo Penta 5.0 GXI. Have the manual and am learning... Thank you for any advise and wise counsel you can offer. This is my first forum post ever and look forward to the response.

 

[Scott Danforth]

salt water boat? if so, replace your exhaust. manifolds and elbows

you have one really wet valve stem and some that are a bit rusty, however not too bad. most importantly the exhaust manifold mating surfaces look rough.

pull the heads and take them in to get rebuilt. get a quote first, as new vortec heads are about $600

as for the impeller, the first thing you should have done when you boat was replace the impeller and bellows. you now have to find all the bits.

 

[Lou C]

The main risk with this problem is rough running and low compression due to sticky valves. This would likely show up in the compression test. If you have rough running at idle and low speeds esp after a cold start then for sure do a compression test to verify the issue. Then the heads need to come off a valve job done and if the engine had a bad overheat I'd have the machine shop check the heads for cracks. Overheats often damage head gaskets which may blow a few seasons later.

however if it runs well and has normal compression you could just run it and keep in mind in salt water you must maintain the exhaust system; this usually means replacing the risers & manifolds every 5-7 seasons or as soon as you see rust trails seeping from the joint between the riser and manifold. If there are signs of leakage on the inside there can be leakage on the inside ---> water in a cyl via an open exhaust valve.

also check the engine oil for water in the oil (look at dipstick for higher than normal level and milky oil and look in the valve cover after removing the oil cap. If so change oil several times till it stays clear.
This is why fogging the engine (if a carb engine) can prevent this, you can get internal engine rust if stored in damp climates even if the exhaust does not leak.

 

[herring627]

Thank you Scott! - Intent to sand down mating surface. Pulling out the head gaskets you say - doesn't this require removing the engine? It's a pity there isn't any "how to" Youtube videos on i/o engines - gasket maintenance.

Thank you Lou - I get the check oil part but compression test? Any place you can point me to for how to do this? Smoke was billowing out of the haul for a good 10 minutes followed by burring sound for another 15 minutes! How complicated is pulling the head gaskets out? Does the engine need to come out for this?

 

[Lou C]

The engine does not have to come out if you have good access. The compression test is a basic test that you can learn from any shop manual. I advise getting a hold of a Chevy engine manual and lean the right way.


That sounds like a bad overheat, that probably scorched the rubber exhaust hoses that go from the risers to the elbow coupler and from that to the exhaust Y pipe. I had basically the same thing minus the smoke, my engine ran fine for 2 more seasons then it blew both head gaskets. I wound up doing a top end overhaul. It was not really hard, but it is a very detail oriented job, where you must be careful not to break fasteners (head bolts and manifold bolts) keep all the parts organized, CLEAN everything before you start taking it apart, then learn how to work with a local machine shop because you will need them to check the heads, if cracked I'd replace rather than repair. That's what I wound up doing. Not really a job for a beginner, but for an advanced do it yourselfer who has worked on Chevrolet small blocks before (one of the simplest engines ever designed) not a hard job. #1 is clean clean clean, clean out the cyl head bolt threads in the block and #2 is to learn how to measure parts for warpage of the sealing surfaces with a mechanic's straight edge and feeler gauges.
Here are pix of my tear down, ya feel up to this?

 

[herring627]

Well I am up for learning how to do the compression test. So you say learn from a Chevy manual (or perhaps a Youtube video in the same vain). This should provide me with the education I need for this "basic test."

 

[Lou C]

After I had the overheat, I did a comp test and the results were normal, and there was no water in the oil. So I just ran it, knowing that there could have been damage but the engine was old then anyway. It made it through the rest of '13, all of '14 &'15, and ran fine up until August of '16, that's when it blew the head gaskets, I found water in a cyl and that was it. So finally got to take an engine apart. Came out well actually, but took a lot of time because of all the skills you need to learn. In your case if the comp test is OK, there is no water in the oil, and it does not make odd noises or burn oil (one valve looked real oily in your pix, could be a bad valve seal, or worn valve stem/guide) and it runs well I'd probably run it keeping in mind that you may have to do at least a top engine overhaul at some point.

 

[herring627]

Thanks Lou, I need this boat to run well for one more year and will be trading up, somebody else's problem then (which I will disclose). I'll post the compression settings once I get them.

 

[Scott Danforth]

You cant "sand down" the ports on the head, you can take the heads in to a machine shop and have the ports surfaced. Sanding would give you un-equal surfaces and the exhaust gaskets will fail.

I highly recommend you talk to a mechanic if pulling the heads seams daunting.

 

[herring627]

salt water boat? ... most importantly the exhaust manifold mating surfaces look rough.

pull the heads and take them in to get rebuilt. ...

The sanding I was referring to was the mating surface. Local boat place recommended this, of course you a block sander to get an even surface. My concern would be dust and rust debris getting to the internal parts. I didn't ask this question then, so maybe you can answer.

 

[herring627]

The engine does not have to come out if you have good access. The compression test is a basic test that you can learn from any shop manual.

Ya a bunch of questions on that one. I start it in a separate thread...