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HELP AQ125 overheating everything checks out

C

chief_wiggum

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"Okay, please bear with me for

"Okay, please bear with me for the background:

The Boat: 1986 Bayliner 19' with the 2.1l Volvo engine. This is a friends boat, not mine, so I can't tell you how exact the series of events was, but here's the story:

"We went out on the lake, and the boat was running good, but then steam / smoke started coming out from the engine cover. Then the engine cover blew off from the force of the radiator cap blowing off, and water was gushing like a geyser .. We let it cool off for a while, and then drove it slowly to a cove for inspection. There we saw oil in the bilge, along with a bunch of water. the bilge pump wasn't working ... blah blah blah...."

So, that's the story I got.

The first thing I saw was that he had put some epoxy on a fitting on the seawater strainer to try and stave off a leak. (didn't work)
What I did:
1. compression check:

cyl 1 130
cyl 2 105
cyl 3 80 YIKES!
cyl 4 112

Checked / replaced seawater impeller and seal:
checked circ pump
removed t-stat and checked (opens fine)
re-assembled and replaced all water gaskets that needed it.
replaced pressure cap with new 13# cap.

Started it up in the driveway, and ran it on the hose for 1/2 hour: ran great, temp never went about 175.

Took it out for a lake test:. ran great at low speed BUT as soon as I cleared no-wake zone, and got up on plane, the temp gauge pegged. I shut it down, and let it cool off for a while. and brought it back in.

While I had it in the water, I removed the cap from the seawater strainer to verify water (yes) I also removed the heat-exchanger cap, refilled with water and observed bubbles, and an almost immediate positve pressure. Enough to make the cap leak when it wasn't even hot.

Soo.. my conclusion at this point was a blown had gasket / cracked head / block, etc.

I tore the engine down, and, althouth I could not see evidence of a leaking head gasket, the head IS warped pretty bad.

Also the exhaust manifold is very corroded where it connects to the bellows.

So, what *should* I expect in the way of corrosion / etc on the exhaust ? and in the scheme of things will that affect anything ?

I *think* that what happened is that the boat initially overheated, either from a bad pressure cap (looked like OEM and fit horrible) an old seawater impeller, or maybe just plain old having no water / coolant in the tank since the owner had NO IDEA that there should be any ! !

When the boat super-overheated the head warped, which is what is causing 1: bubbles in the coolant tank 2: low compression on the 1 cylinder and 3: the overheating under power.

Am I on the right track here ? is there something I am missing ? Any / all suggestions / comments welcome.

Thanks"
 
Blown head gasket and/or warpe

Blown head gasket and/or warped or cracked head...... THAT SUX!!!!!
But not the end of the world!!!!
 
"For starters, it seems to me

"For starters, it seems to me that the raw water hose connector in the outdrive may be corroded/perforated, and the raw water pump is sucking air once the boat goes on the plane. Typical VP AQ problem but easy to fix. This is the part you may need to replace:

http://www.marineengine.com/parts/part_details.php?pnum=SIE18-2778&returntopage= sierra_marine/sierra00826.htm

It also seems that the exhaust manifold may be internally corroded and plugged-up. Usually the best solution is a new manifold; "boiling" a scaled-up manifold in a radiator shop often does not work and if it is really wasted away it will get perforated during the chemical cleaning process.

You can install an automotive head if the one you have cannot be salvaged, but you will have to install the original camshaft (an automotive camshaft will not work). Also, if the engine is damaged, consider getting an automotive B21 engine in good condition and marinizing it. Do a search in the forum, this has been discussed many times."
 
"Yeah, I'm familiar (w

"Yeah, I'm familiar (way too) with the seawater intake elbow problem.. That was one of the first things I looked at, but it appears that a PO has replaced ALL the rubber (U-joint bellows, exhaust bellows) and the seawater hose AND fitting. it ALL looks brand new.

I think you are probably right about the exhaust man. it looks VERY eaten away right at the point where it connects to the rubber. Also that port on the manifold looks as if it has been "wet" for quite a while.

I'm going to take the head to a machine shop to get the opinion if it can be milled or not. The valves / cam etc are incredibly clean so it would be nice to be able to cut it and re-install it.

What's the best source for a new exhaust manifold? Is it even worth looking at used ones, or is it typical for them all to be junk that are that old?

Thanks for the input!"
 
 
"Well, the boat won't ever

"Well, the boat won't ever see salt water, but I get the point


The first link is kind of a scary price, but the ebay one isn't *too* bad.

But after thinking about it.. this manifold is corroded pretty bad where it connects to the bellows, BUT .. who cares ? I mean what's the chance for failure with it ? the water / exhaust mix at that point, so it's not too important to have a "clean" flange as far as I can see.

I "bench tested" the manifold by running water into the seawater port, and seeing if any came out the exhaust ports.. (it didn't) Thoughts ? ??"
 
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