Rocky buildup in exhaust manifold?

[scrumper]

Intake manifold, then head. The intake manifold is the bit I'm struggling with now - then the heads should hopefully lift out easy (though I'm sure after 20 years they'll be stuck fast to the gasket and need a little persuasion.)

EDIT: Thanks for the advice. There's a gap between the manual and practice; I appreciate the benefit of your various experiences here. I'm from England originally and the biggest engine I ever worked on before was a 1500CC 4 cylinder Fiat motor in the early 90s.

 

[370Dancer]

I thought about that (handles) but the threaded parts are in the block, not the manifold. Next time I'm down I'll look again and maybe there'll be some threaded fittings I can use that I haven't considered.

ah sorry. I was talking about handling the heads, not the intake. RTV your best friend putting it on, and your worst enemy when trying to take it off.

 

[scoflaw]

There will be a 1/4" gap between the intake and the china wall on the block. Get a pry bar in there.

 

[Scott215]

You're going to be replacing the t-stat anyway so you should have the t-stat housing off so that's how we used to do it on street cars

 

[Scott215]

You're pulling a heads just put a couple long bolts in and raise your leverage right there I didn't think you were pulling the heads

 

[scrumper]

All worked out ok in the end, thanks for the push guys.

With the t-stat assembly off, the intake manifold came off easily. Weight was not unmanageable. Heads more of a pain but mostly because of all the crap Mercruiser bolts to them and all the stuff that's bolted to that in turn - alternator, idler, and heat exchanger brackets, the coil, etc.

Heads off to a local machinist for reconditioning - I was good with doing a simple valve job but the cost isn't bad and I might as well have it done professionally. I'll be busy enough cleaning the head gasket junk off the block. The combustion chambers and valves have surface rust on the low comp. cylinders and a bit of rust gunk collected at the blocked-off end of the coolant passage too (perhaps from corrosion in the old heat exchanger that I'd swapped out in 2021.)

 

[370Dancer]

All worked out ok in the end, thanks for the push guys.

With the t-stat assembly off, the intake manifold came off easily. Weight was not unmanageable. Heads more of a pain but mostly because of all the crap Mercruiser bolts to them and all the stuff that's bolted to that in turn - alternator, idler, and heat exchanger brackets, the coil, etc.
.You got that sh^t right !!

 

[scrumper]

Haha yes. It's horrible isn't it. The harness is like wrestling a twenty headed snake. Mine is held down at both ends of the engine so I can't "tidy" it all away to one end like you - in fact today I dunked the TPS connector in a puddle of oil.

I like your lump hammer. Used mine rather more than I was expecting to.

 

[370Dancer]

got my intake off in 2 strokes of my "jaws of life" hydraulic press from Harbor Freight. No more pry bars.....

 

[scrumper]

Nice tool, looks like it'd be harder to wedge into a narrow gap than a pry bar though. But more even force over a larger area is good.

And I've now gone from this - including clogged up end of the head coolant passage (at the end which is blocked off in the intake manifold) resulting from I think a period before my ownership of ancient coolant since the first thing I did to the boat was change the heat exchangers:

and:

To this:

Courtesy of an old-school machine shop in the Bronx that three separate people recommended to me. Not new, but valves ground, new seals, stems and guides cleaned, rust removed and ready to get back on.

Reassembly next, after 5 days of continuous heavy rain kept me off the boat. I took the time to give the intake manifold a really good clean, touched up some paint, painted the heads, cleaned the thermostat housing and hoses.

 

[Scott215]

Some cooling jackets don't go into the block, small Chevy's I think

 

[scoflaw]

Those valves look rough, could create hot spots

 

[scrumper]

Right! The good news is that we're back in business, everything running well on a test run tonight. Weather has been awful for finding time but I was able to sneak out here and there. It's taken most of October but the starboard engine is back together.

In the end reassembly wasn't too bad. Adjusting the lifter preload was the most fun part; the least fun was sweating the elbows back on the manifolds. I couldn't find Merc OEMs and I wasn't that pleased with the finish on the Sierras I put on the port engine, so I tried Barrs - USA made, warrantied, and available via Mr. Cool. The quality seemed a little nicer than the Sierras at first glance but the paint finish on the mating surfaces was very thin. Anyway they installed fine. The problem is that, just like the Sierras, the casting isn't exactly the same as Merc's. The Sierras were a little thicker (which created problems mounting the ECM bracket on the port engine); these are a little higher. Just a little, but enough that the hoses were extremely difficult to re-attach - they're so stiff that they were holding the elbow off the manifold so getting a bolt started took forever. I think I need to put new hoses in over the winter, everything is just slightly off. But it all connects and seals so it'll do for now.

On Thursday I tried the first startup. It was awful! The noise of the lifters was horrific. The engine ran like shit too, even after that noise had stopped. Obviously misfiring, rough, 400rpm. So I shut it down and was about to figure out how to remove the entire engine when I remembered the HT leads were from 2009 and some terminals were split. So I ordered a new set of leads and changed out the oil.

Second startup today with the new leads was much better. Smooth, quiet lifters, no misfires, lovely. After a run up to temperature, a quick coolant flush - difficult, because the drain plugs are tucked away very deep - and another oil change, the family and I took her out to the harbor, ran up on plane for a bit to make sure all was good, and headed back. The Sound wasn't nice by the time we got out and my daughter and I are both fighting off Covid so it was a quick one. Back to the dock and another oil change. The first change last week produced pure garbage milkshake, only a little better on the second, but the third change looked fine. At my yard head mechanic's suggestion I had replaced a quart of oil with Marvel Mystery Oil each time and it seems to have a done a good job of flushing it. I did the same on the port engine and that too looked much better.

At idle, displacing at 12kts, and up on plane the engines seemed fine. Starboard was a little hotter at 167 but that settled down to normal 165 after a few minutes. I think that I haven't quite got enough coolant in there. It would only take 4 gallons and there should be 5.5. I need to burp it.

All in all this was all fairly major surgery and I'm pleased to have got through it. It's been a big confidence booster too: I've learned so much more about these engines than I knew before and that in turn makes me a lot more comfortable that I will be able to work on the next problem that comes up.

There's no season left now, but I'll be happy to winterize a working boat rather than craning out a motor to work on over the winter. Thanks for the good advice here