driveshaft problems on '73 Mercruiser


Old 06-29-05, 09:09 PM
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driveshaft problems on '73 Mercruiser

I found something that kind of sounds like the problem I have. Not sure, I'll post this first then describe it in my own words.

Outdrive: As soon as you mentioned you couldn't find an oil drain on your drive, I knew what the problem would be. Loss of gearcase oil in Mercruiser Outdrives is one of their big killers, and there are many ways that outdrive can loose it's oil as a fuction of it's design and it's operating environment. You need to check the oil constantly, and change it often. I can almost assure you that if you check your upper case, you will discover that your two main gears (the drive and driven gear)are totally destroyed. I check the oil on my outdrive almost every time I take it out. Were you out on the water when the drive failed? If you lose oil, the gears will burn up on you while you're underway, and it feels like you've popped out of gear or spun a prop. The source of the problem: A seal failure. One of the classic seal failures is monofilament line around your prop shaft. It tears the shaft seal to pieces in minutes, and your gears shortly thereafter. Look for fishing line behind your prop.
Alright. Bought this boat of mine off my sister. It's a '73 Century Trident with the Mercruiser 3.0 140hp four cylinder inboard/outboard. I dropped a new engine in it as my brother in law removed the old one. We replaced it with a '75 3.0 140 hp. Took it out once and the stern drive water pump failed. Fixed it with my Clymer manual. Took it out again. It ran for 15 to 20 minutes and then it suddenly felt like it came out of gear. Also the temp jumped really fast. Shut it down, let it cool and tried to restart it just to see if it would engage. Nothing and the temp was rising.

So today I finally took the boat apart. The lower unit's water pump is as new looking as it was the day I put it last summer. So the impeller isn't fried. So I got my Clymer out and tried to think of what else it could be. I took off the Drive housing, but haven't opened the cover yet. I had thought maybe the drive shaft broke apart at the U joint, but it looks and feels fine. What should I check next? The Clymer doesn't have very good troubleshooting tips at all. Any help would be appreciated.
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Old 06-30-05, 11:34 AM
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Update: I took the top cover off the drive housing today. The gears are intact and spin when I turn the U joint. I'm at a complete loss about what's wrong.

One thing I should have mentioned in the first post; When I tried to put the boat into forward or reverse, the motor would stall.

Again, I'd appreciate any advise or help. Thank you.

Old 07-01-05, 01:54 PM
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Still looking for help, if anyone has anything to add, it'd be greatly appreciated. If you would want to talk to me about off the forums, you can get hold of me on AIM, my screen name is SilverGA2001, or my email address; [email protected]. I can provide pictures of what I've done so far to go along with descriptions.

Again any information would be helpful. Thank you.
Old 07-03-05, 09:25 AM
Join Date: Apr 2005
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It could be your engine coupler. If coupler went bad there would be no power to the lower unit to turn the impeller. That is just a guess but worth checking out. let us no what you find. Good luck. MIKE
Old 07-03-05, 03:06 PM
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Originally Posted by mcope66
It could be your engine coupler. If coupler went bad there would be no power to the lower unit to turn the impeller. That is just a guess but worth checking out. let us no what you find. Good luck. MIKE
Thanks Mike. After looking at it some more, I do believe it's the engine coupler. The stern drive seems to be in order, and everything doing as supposed to.

To replace the engine coupler, you do have to pull the engine out, correct? I found the part online for 175. I might be able to get one off my neighbor for free though, he has a mid to late 70's 3.0 with the same outboard unit as mine that he has no stern drive for. He said I'm welcomed to it if I can pull the engines to get to it.

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