Blown headgasket

Fr. Frank · #1 09-21-2015, 09:16 AM

Well, after buying this boat last year for $10.40, (plus the $1300 it cost me to go get it) replacing the manifold and riser, carburetor, distributor, putting new upper & lower cables on it & new lower unit bellows, installing a new fresh water tank, sink spigot and pump, and having the canvas sent off to be re-sewn, I finally decided it was ready for a good water test.
I let it burble nicely at the dock in gear for about 1/2 hour at 800-1000 rpms, and fine-tuned the spark advance, and set the dwell on the points perfectly. My deacons both arrived for a little jaunt up and down the bay, and off we went, through the idle zone, and up on plane, 3200 rpms cruise. Wonderful! For about 3 minutes.
Began losing power, came down off plane. Motor sounding rough, loud knocking sound. Shut it off. Opened the engine cover. small amount of steam. Looked for loose hose. Hmmm.
Re-started the motor, it started immediately. Looked at the motor, saw small amount of water & bubbles coming out between the cylinder head and block by #2 cylinder. Shut motor off. pulled spark plugs on all four cylinders. #1 and #4 look normal (some soot), #2 and #3 are squeaky clean. replace plugs, restart motor, pull plug wires one at a time. Power loss pulling #1 & #4, pulling #2 or #3 gives very little change.
Bummer.

Terry England · #2 09-21-2015, 10:23 AM

Padre, If you pull the head be sure to check the cyliner walls. The Mexican-Mercuriser cast iron blocks had notoriously thin castings on the cylinder walls. I would recomend not boring the block on a rebuild because that just increases the chance of a vertical crack in the cylinder walls.

I found it quite difficult to "Go In Peace" with my 140 Mercruiser - in fact on many occations it caused me to take the Lord's name in vane!! (I'm "clawing" my way back to Grace with my E-Tec)

<')))>< <')))>< <')))><

Fr. Frank · #3 09-22-2015, 08:48 AM

Thanks. From my time as a marina manager, I'm familiar with the issues with the cylinder walls on those old Chevy 2.5 and 3.0 engines. As this motor is 46 years old, and has spent it's entire life in saltwater, I'm pretty sure of what I'll find when I pull the cylinder head on Thursday. I fogged the motor just in case it was repairable, but I ain't holdin' my breath.
One good thing is that the oil is clean with no water in the oil whatsoever.
I found a used 1983 Checkmate Enticer 16', with a 130 hp Mercruiser 3.0 freshwater motor outside of Eufala, AL, about 3 hours from here, for $1K. Original owner estimates it has between 200 and 400 hours on it, and it spent it's whole life on the reservoir. I learned of the motor when I heard the story from a clergy colleague of how the owner's grandson was drinking and ran into a tree... 30' from shore.