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Engine won't turn over

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baitbag

Member
I have a 1986 boat with a 350 chevy mercruiser engine operating in salt water and the engine is raw water cooled. The engine has been running great with normal oil pressure and water temp. I took it for a ride a few days ago and it ran well without incident. When I went to restart it later that day, the engine wouldn't turn over. I put a brand new starter on it and had the same problem. The boat is well maintained and I even put in a new battery this spring. I put a wrench on the crank and found that I could turn over the engine with A LOT OF EFFORT. It definitely wasn't normal! I checked the oil and the level was normal with no trace of water on the dipstick. The engine was replaced about 10 years ago and I replaced the exhaust manifolds 3 years ago. The engine was replaced with a brand new one. Also last year I replaced the gimbal bearing and one of the u-joints. I'm trying to troubleshoot the cause of the problem. This spring I changed the gear oil in the outdrive and saw traces of water in the old gear oil. It was not excessive, so I just refilled it with oil and launched the boat. I'm not 100% sure if the problem is the engine or if the slight water contamination in the gear oil is ruining the bearings in the upper gear case and causing things to bind up there. Has anyone dealt with problem before? I suspect a small internal water leak in the engine and if anyone has some troubleshooting tips regarding this please let me know what you have.

baitbag
 
You discussed the mechanical things but how about the electrical? Have you tried placing a voltmeter between the starter’s main battery connection and ground while somehow trying to start the engine? It could be something simple such as a poor connection somewhere. Does the starter even attempt to turn the flywheel?
 
The old Perko MBSSs have small contacts and weak contact spring pressure. If this is a Perko MBSS, try switching it back and forth a few times in hopes of gaining better contact.
And yes..... look at all battery cable connections.... both Positive and Negative.

If still NO GO...... perhaps remove the drive and give it a try. If it turns over and fires up, you'll know what the cause is.

While the drive is off, you can also replace the bellows, etc.
 
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1 NEVER USE THE CRANK NOSE BOLT
pull the spark plugs and try spinning the motor
if no movement , then pull the drive and try to spin/start the motor
When you changed the gear oil , you FILLED from the bottom until; it came out the top?
 
I don't see where you tested or replaced the salve solenoid for the starter...often located on the top of the engine. To test ( the crude but effective way)... temporarily bridge the two heavy duty terminals on the solenoid with a big screwdriver... engine should crank. IF it does,
1) defective start position on the ignition switch
2) bad wiring ignition switch to slave solenoid
3) defectiv4e salve solenoid.

If it does not crank with shorted big lugs on solenoid
1) If you saw a big spark when you did this, +12 v source ok... if not check wiring
2) engine seized
3) defective starter
 
The gear oil was pumped in from the bottom until it came out of the top plug. I'm going to haul out the boat and take out the plugs and remove the outdrive if necessary. If there is a small internal leak of water into the engine and given the fact that the engine is about ten years old, is there a particular spot on the engine that would rust through first? The previous owner of the boat had a new engine installed and I believe that all the other accessories ( starter alternator, intake manifold, etc.) were transferred from the original engine. If the intake manifold is rusted through and dripping into the engine, I should be able to detect this problem when I take out the plugs ??? Until I haul out the boat and check the things you mentioned, I am bracing for the worst case scenario which is a raw water leak into the engine. If I remove the spark plugs and find signs of water in the cylinder(s), then how do I pinpoint the source of the leak?

baitbag
 
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