'73 Mercruiser sterndrive problems

[silverga01]

I hope I put this in the right section, as I didn't feel it belonged in the Mercury Outboard page.<br /><br />I have a '73 3.0 140hp Mercruiser engine and stern drive. I bought it last year from my sister, and first thing we did was replace the impeller. We took it to the lake and were running for 15 minutes or so when it felt like it slipped out of gear. The prop would not re-engage and the temp started rising. I thought I'd burnt up the new impeller. That was the last time it was in the water before being stored for the winter. One thing to note is that the engine will idle and rev fine, but if you attempt to put it in forward or reverse gear, the engine stalls.<br /><br />I took it apart 2 days ago, mostly to check the impeller. The impeller is as good as the day I put it in last summer. It is not damaged and the pump body is fine. Somehow the shaft the impeller is located on is not turning, causing it to overheat. So I took off the Drive housing to investigate. I've been using a Clymer manual to do all this work. The only problem is the Clymer has very few troubleshooting tips. It's more or less disassemble and reassemble. <br /><br />After removing the top cover on the drive house, the drive and driven gears are intact. The U Joint seems fine. If turned, the spline at the bottom turns, which would turn the driveshaft in the gear house with the impeller. I am at a complete loss as to what to do next. Any help would be greatly appreciated.<br /><br />Thank you,<br /><br />Matt

 

[Don S]

Re: '73 Mercruiser sterndrive problems

Sounds like the splines may have gone out of the coupler.<br />Pull the drive and look inside. If the coupler looks smooth inside like the upper picture, then you need a new one.<br />With a spun coupler like that, you should also see metal shavings around the coupler.<br /><br />

 

[Haut Medoc]

Re: '73 Mercruiser sterndrive problems

Don, where do you get these pictures from? Your diagnostic abilities always amaze me.................J

 

[Trent]

Re: '73 Mercruiser sterndrive problems

I agree with Don.. The overheating gives it away. Time to pull the engine out to replace the coupler.<br />Make sure to have the engine alignment checked because its the number one cause of coupler failure.

 

[silverga01]

Re: '73 Mercruiser sterndrive problems

I tried something last night, I think it was last night. I disconnected the distributor so the engine would not spark and turn over. Then I turned it over with the starter and had someone check to see if the splines inside the bell housing (I believe that's what my Clymer calls it, it's what's left after you take the U Joint shaft out with the Drive house). The splines were moving with the rotation of the engine. This coupler, is this the short driveshaft with 2 female ends for the engine spline and the U joint spline? Would it move like I mentioned if it was the source of the failure? Also this boat has been repowered by my sister and her husband, they dropped in another 3.0 in the past. If this coupler is shot, the only way to replace it is to pull the engine? Thanks for the answers so far, if you can answer a few more, it'd greatly help me understand this. Thank you.<br /><br />Matt

 

[silverga01]

Re: '73 Mercruiser sterndrive problems

Also, I can provide pictures of any of the parts if it could help.

 

[Haut Medoc]

Re: '73 Mercruiser sterndrive problems

The coupler will still spin because it is no longer under load. Yes, the engine must be removed to replace the coupler and will have to be re-aligned afterward. Mis-alignment is what probably caused its failure....J

 

[silverga01]

Re: '73 Mercruiser sterndrive problems

Well that's my worst fear I guess. Thanks everyone. I called some marinas around me and they all said they don't like to work on boats this old. Things keep going wrong on them and they become money pits and the customer gets angry. Tried to tell them I wouldn't be angry as I've already taken the stern drive off for them, but they still weren't interested. I guess this might be the end of the boat for me. I didn't even get to enjoy one ride in it.<br /><br />Again, thank you all for the help. I'm happy to just know what the problem is now.<br /><br />Matt

 

[Haut Medoc]

Re: '73 Mercruiser sterndrive problems

I would not junk the boat because of a bad coupler. Removing the engine is not as hard as you think especially with a 4 cylinder...It is very do-able if you have time & mechanical inclination. Couplers aren't too expensive...J

 

[silverga01]

Re: '73 Mercruiser sterndrive problems

I just don't think I'll be able to do the work myself or be able to pay to have it done. I really hate to junk this boat, but I've only got 1,000 tied into it at this point. I dunno, I'll have to do some thinking. I may be able to get the parts for free though from my neighbor who has the same engine and stern drive setup in a boat he got that came with the trailer he wanted. It's missing the drive housing and the gear housing, but it still has the coupler. At least that'd be a help.

 

[Trent]

Re: '73 Mercruiser sterndrive problems

I personally would not use a used coupler... <br /><br /> web page