Rocky buildup in exhaust manifold?

The only common thing between the two manifolds that got wet is that the T barb fittings for the dripless shaft seals are attached to those risers. I can't see how that would be responsible though, it's blocked off by the gasket.
 
Compression is great across the board on the port engine - I'm going to go ahead and reassemble that one with new manifolds and elbows and plugs and see what happens. I'm slowly draining the oil (I can't run the engine to warm it up) and it looks like shit. Looks crystal clear on the dipstick but what's coming out is satan's milkshake. Not even worth getting it analyzed, it's clearly full of water. So I'll refill with good oil, start and, if it's good, run up to temperature, then change the oil again.

On the starboard engine, two cylinders are very low (60 and 90) and I can hear a puff during the compression test that isn't happening on the other cylinders which makes me think the exhaust valves aren't seating properly. I'm not sure what to do about that.
 
scrumper said:
Compression is great across the board on the port engine - I'm going to go ahead and reassemble that one with new manifolds and elbows and plugs and see what happens. I'm slowly draining the oil (I can't run the engine to warm it up) and it looks like shit. Looks crystal clear on the dipstick but what's coming out is satan's milkshake. Not even worth getting it analyzed, it's clearly full of water. So I'll refill with good oil, start and, if it's good, run up to temperature, then change the oil again.

On the starboard engine, two cylinders are very low (60 and 90) and I can hear a puff during the compression test that isn't happening on the other cylinders which makes me think the exhaust valves aren't seating properly. I'm not sure what to do about that.
Click to expand...
Going to have to pull the heads on that engine and have them redone.
 
Yep. Came to that conclusion too. Going to run a leakdown test first, I am hoping to hear a puff through the exhaust which means I will pull the heads and do a valve job and a cleanup. If it's leaking out through the piston rings then I'll have to call in help.

Got the oil out of the port engine today. Then poured in a fresh gallon, but now the stuff on the dipstick is milky so I'll drain this lot out too. I expect I'll need a few changes.
 
Did you ever do the measurements called for in the install manual to see whether everything was sufficiently above the water line with the correct down angles?
 
Yes, though not completely yet. It's well over 13" waterline to elbow top which is the critical safety dimension in the install book. I haven't yet measured then angle throughout the entire run to make sure the whole length is angled right however.
 
Can you fit a 1.7 inch spacer. That's what my exhaust has
 
Didn't know there _were_ 1.7" spacers. I think not but I will measure - that could be a help. Thanks for the steer.

Last night I found that there are no shutters at all in the exhaust system. It exits above the waterline on the hull sides but with the limited down angle it's quite easy for water to slosh forward in a following sea or when coming off plane too fast - I think that's what happened to me: caught a wave , rolled a bit to port, and water came forward enough to be ingested.

There is room to put a 4" internal shutter between the Y piece and the collector/muffler box. Am going to discuss with the yard head mechanic who apparently is experienced with repower exhausts just to make sure there's no issues with that - shouldn't be as it's very much like the arrangement you get on a sterndrive.
 
I have 1.7 inch spacers and 14 degree exhaust risers. Is your set up how it came stock. Or do you not know. I did not know there was 7 and 14 degree until I looked up my exhaust
 
Does your exhaust exit through transom or out drives, flappers would definitely help
 
Stock was big block carb'ed 454s with a different exhaust, it's been repowered since.

7 degree elbows aren't specced now: Merc redesigned to 14 degrees after a lot of warranty claims for reversion water damage. Bernard above has some commentary about that.

I have straight shaft inboards; exhaust exits above the waterline on the hull sides just ahead of the transom.
 
Got the port engine reassembled last night and test fired it. Started great, a little rough for a few seconds but settled down after a blip or two on the throttle to 650rpm idle. I ran it up to temp, then it idled bang on 600 per the book. Couple of minor leaks from hose clamps I hadn't tightened properly but otherwise running well.

Changed the oil. Still a little milky looking (this is the second change but only the first change since I've been able to run it, so I'll do it again.)

On to the starboard engine now - leakdown test first, and then if that indicates valves are the problem I'll pull the bad head and try and save the last of the season by having a local machine shop recondition it.

EDIT: Forgot to say, I replaced OEM Mercruiser manifolds with new Sierra parts. The Sierra casting is a little wider, with the result that the ECM bracket on the riser now fouls the central support ridge in my engine hatch. I'll have to put in longer screws and spacers to bring it back to where it was with the OEM manifolds. There's always something little like that.
 
The project continues. Leakdown test showed significant leakage out of the exhaust port on the two cylinders that had poor compression. So I started to pull the heads. And holy hell, the service manual is a giant Book of Lies written by bastards. Just nine steps to remove the intake manifold? Maybe on an engine that has no accessories or wiring harnesses or circuit breakers or coolant hoses or anything else that might mean it could start and turn under its own power. I still haven't got it off after three hours of swearing at it. I've managed to make it move a quarter inch on the back end of the engine; I cannot figure out how to budge it off the front. Then it got dark at like 7:30 because of the fucking latitude I stupidly chose to live in, and now the edge of a hurricane is pissing water all over my slip and I'm stuck at home with my kids because my wife is traveling and I can't leave them alone to go work on it.

I think I have to pull the entire thermostat assembly off, which isn't a big deal considering the chaos of parts and wires and hoses that I've already caused.

I briefly considered sliding the head out from under the intake manifold (which, per above, is at least loose), but that won't help much as I'll still have to pop the intake off to re-seal it and replace gaskets when I fix (or replace) the bad head.

Fuck all of this, I hate boats.
 
If you have all 12 bolts out of the intake manifold it should come off it's going to be stuck on there but it should come up . Especially if it's been on there for a while it will be very hard to pull off
 
Yeah it's moving, it's just awkward as hell, tons of stuff in the way too. I was there just now (to get the head casting number in response to your question on my other thread) and was able to wiggle it about. I think fresh muscles and daylight made it a bit more tractable.

I'm not sure how I can physically lift it out. There's nothing to grab on to, and it seems like it weighs a *lot*. I might be able to slide a strap under it perhaps. Ratchet it up using a hatch rail.
 
scrumper said:
Yeah it's moving, it's just awkward as hell, tons of stuff in the way too. I was there just now (to get the head casting number in response to your question on my other thread) and was able to wiggle it about. I think fresh muscles and daylight made it a bit more tractable.

I'm not sure how I can physically lift it out. There's nothing to grab on to, and it seems like it weighs a *lot*. I might be able to slide a strap under it perhaps. Ratchet it up using a hatch rail.
Click to expand...
screw a couple of bolts to the ends of the head for handles. 2 people are better than one. Make sure you have a landing place for it.
 
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.
 
Put one hand in the thermostat hole and then grab the bottom back the part of it
 
Good idea, I'll try that. Wasn't committed to pulling the stat but it's a trivial thing at this point. Cheers Scott.
 
Are we talking about the intake manifold or the head? Either way, a piece of chain, a piece of hose or PVC pipe and some bolts (carb-T/body or rocker) and some washers will be you lifting/leverage friend.
A cross brace with a come along/chain fall would be extra set up work but would cut the body load for sure.
 
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