Hi all,
Been having trouble with our '87 Merc 50 hp 3 cyl outboard. We had a pretty bad overheat and discovered the impeller had gone bad - it was pumping water but not enough to properly cool the engine. After we replaced the impeller, we also did a compression test on the cylinders to see where we were at - all three read 110 PSI which seems ok for a motor of this age. However, we realized after the fact that we made the stupid mistake of not properly grounding the spark plug wires from the coils when we cranked the motor for the compression test. These are new coils that we replaced a couple months ago at the beginning of the season just because the original ones were very old and we had a cylinder randomly dropping out while under way - after replacing the coils the engine ran great until the overheat problem.
Now, the motor is not starting at all. We are seeing a tiny spark from the plugs when pulled (and grounded against the head) but haven't tested with a gap tester. Is it possible that failing to ground the coil wires during the compression check has burned out the coils? Could it also have burned out the switchbox? I've read conflicting things that a switchbox either works or it doesn't, and some things saying it could be intermittently or poorly working. How far up the chain of ignition could we have damaged things? Stator/trigger as well? Could the initial overheat have also compromised the stator? Just wondering where to start and what to test first. We are amateurs but this is a project motor for us. Thanks very much!
Been having trouble with our '87 Merc 50 hp 3 cyl outboard. We had a pretty bad overheat and discovered the impeller had gone bad - it was pumping water but not enough to properly cool the engine. After we replaced the impeller, we also did a compression test on the cylinders to see where we were at - all three read 110 PSI which seems ok for a motor of this age. However, we realized after the fact that we made the stupid mistake of not properly grounding the spark plug wires from the coils when we cranked the motor for the compression test. These are new coils that we replaced a couple months ago at the beginning of the season just because the original ones were very old and we had a cylinder randomly dropping out while under way - after replacing the coils the engine ran great until the overheat problem.
Now, the motor is not starting at all. We are seeing a tiny spark from the plugs when pulled (and grounded against the head) but haven't tested with a gap tester. Is it possible that failing to ground the coil wires during the compression check has burned out the coils? Could it also have burned out the switchbox? I've read conflicting things that a switchbox either works or it doesn't, and some things saying it could be intermittently or poorly working. How far up the chain of ignition could we have damaged things? Stator/trigger as well? Could the initial overheat have also compromised the stator? Just wondering where to start and what to test first. We are amateurs but this is a project motor for us. Thanks very much!
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