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4.3 mercruiser hydro lock

tommy8604

tommy8604

New member
ok well ill start from the beginning. Last year i bought a 2000 Bayliner Capri with a 4.3l Mercruiser, the motor was bad at that time but i like to buy broke things to get cheap. So i bought a used motor and put in it and used everything off the original motor besides block and heads. (never removed the first head bolt). So we completed the motor swap and it fired right up and ran perfect besides needing a little timing and carb adjustments. So we got two boats just in case and took it out and it ran perfect:). so the next day i thought it did so good that we would just take it out, well we started kneeboarding behind it and at the end of the day go to leave and it wont turn over:mad:. so i thought from all the starting and stopping the battery was low. finally limp it back and charge the battery and rebuild the starter. take it out again and it does perfect again so i thought that fixed it. so over the weekend we all go boating and run it for a good 6 hours and its starting to get dark so go to leave and what do you know it wont turn over again and we were tubing behind it this time so i thought it was the battery going bad. pull it in and charge the battery and still wont turn over:confused:. so i pull all the spark plugs and start to notice they are wet:eek:. all this time the oil level never changing and no water showing on stick. so i pull all the plugs and the right side of the motor has quit a bit of water in it and the left side just had a little. so i turn it over and it cranks over just fine now so i solved that problem but now how is the water getting in there and hope like #&!! i didnt bend the valves.

Im pretty good when it comes to motors so im doing all this work myself. but im hoping and preying that its blown head gaskets. what im asking is what are yalls thoughts on this? Do you think i may get lucky and get away with head gaskets or is it going to get deeper in my pocket (boy i hope not). so im not real sure on how these exhaust on these inboards work. i know that have water flow in them also so could it be in them, the intake, the heads, gaskets?

sorry for making this so long but i know when asking these questions the more info the better

Any advise will be greatly appreciated

Thank you
 
Check the exhaust shutters (flappers) they could have been damaged. If they are ok do a compression test. If that is good the exhaust manifolds may be rotted...pressure test them. Replace them if necessary, esp ecially if they are 10 years old. Don't use GLM. Use Barr or Osco if not Merc.
 
Also i have not done a compression test yet. It got dark on me tonight and wasnt able to complete that, but once done what kind of info will it show me? Im assuming it will have compression do to its been running fine but what will perfect compression, low compression, etc mean when done?
 
On this boat it doesnt have flappers on the back, it exits on the outdrive. but i will do a compression test and look into the exhaust manifolds but not real sure what im looking for in the manifolds.
 
It should have flappers right in front of the "Y" pipe. The compression test should show numbers that are near equal on all cylinders. For example: 150 psi on all cylinders on a fairly new engine. A used engine will have 115 to 140 psi. What is important is they are all nearly equal like 140, 138, 138, 140 on one bank and similar numbers on the other bank 135, 135, 138, 138. The heads should not have one or more of the cylinders off by 15% like 140, 140, 140, 112. Two side-by-side cylinders w/low compression usually means a blown head gasket.
 
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