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Old 12-14-2011, 10:08 AM
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At this point, you need to completely disassemble the engine if you want to use it.

You need to pressure test the block, to look for cracks, caused by fresh water freezing in the block.
Another source of clean water in the crankcase is the engine was in a boat that sank.
Since you have to pull the heads, to check the cylinder walls for rust, once a head is off, measure the stroke. About 3 inches, it is a 302. About 3.5 inches, it is a 351.

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Old 12-14-2011, 08:10 PM
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Thanks for the help. I decided to start ripping it down and inside under the intake the block is marked with a 351. So I do know what engine I am working on for sure. I found that the water had definatley come in through the carb. The base of the carb and the intake ports are rusty as can be and the cylinders had water in them. The water could not have been there all that long because after cleaning it up it did not look to bad. I have it totaly disassembled and I am going to drop it off to be cleaned up and checked out. All of the internals look to be in great shape, so I may have just dodged a bullet. I am going to hone it out and see how it looks, but at worst case I am looking at a minimal bore.
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Old 12-14-2011, 08:57 PM
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You would not think this is true, but the general recommendation on an engine that is swamped, or gone under water, is it to leave it under water until you are ready to tear it down, and dry it, provided you do not leave it under for too long.
The oxygen in the air causes the rust, and the water is a catalyst that enables an electrolytic reaction, that causes the rust. So, an engine under water has a very limited supply of oxygen, and limited rust.

If the water is clean, in many cases you can actually get away with draining it, cranking it with the spark plugs removed, getting the water out of the oil pan, and running the engine again, to build heat, to finish drying the engine out. Change the oil again.

If the engine was running when it went under water, there is a possibility of the engine hydraulic locking, a piston coming up on the compression stroke on a cylinder full of water. The water does not compress, and the piston is stopped immediately. If this happen at idle speeds, no problem. Much faster than idle speeds, and something has got to give. Broken piston, bent rod, sprung or bent crankshaft, something not good.
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Old 12-14-2011, 10:41 PM
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Originally Posted by DanielC
I do not recall ever seeing a 351 with the raw water pump on the front of the crankshaft pulley. Most I have seen have the raw water pump in front of the starter, tucked under the front of the engine. The raw water pump mount is designed so that the pump can be mounted with either end up, and mounting the pump upside down, accommodates the pump to an engine that rotates counterclockwise, viewed from the front of the engine.

I think you misread my post... I was saying that in the photo that shows the crank pulley, the lake pump would be off to the left.

Otherwise I agree. I've put a few of those pumps on backwards in a rush
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Old 01-03-2015, 10:09 PM
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I own a 1986 mastercraft, 351 PleasureCraft marinized, with about 1300hrs on it. A friend of mine also has a 1986 Mastercraft with a Indmar 351. Mine has a belt driven seawater pump the Indmar has a crank mounted/driven seawater pump. Wish I had pictures for reference for you re vacuum advance and so on. Main exterior differences relate to carb and fuel pump venting, as well as alternator being non sparking! Rust does form inside the water jacket even with freshwater only cooling. Amazing how much crap can come out of it each fall. 3 years ago it was missing an exhaust flap and the engine filled with water. Neighbors killed starter and battery trying to start it before figurine out it was full of water. Usual oil changes new starter and away it went. Next year son has overheated it so bad everything between block and the exhaust flaps burnt or melted. (pump on upside down) Still runs 43 mph at 5200 rpm. I'd love to rebuild it and convert to full electronics/injection. Or put something near new in it. Some day.
If I can get out to the lake some time soon I take some pics for reference.

Last edited by 974Runner; 01-03-2015 at 10:20 PM.
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