1973 20hp merc

[ryanc]

-Hello all-<br /><br /> My 1973 mercury outboard (20hp) just recieve a lower unit and 1 carb rebuild by my mechine this pass summer. When i took him the motor, it had no lower unit on it. He installed lower unit and re-build the carb. When i got the motor back from him it made a grinding noise. This noise made me lose alot of horsepower. So i took it back to him and he said that it was the main bearing of the motor. This also was causing the loss of power.!!??!!<br /><br /> Now he said "bring it to me in the winter, i'll fix it little of nothing!" Well now he has had it since after thanskgiving and did nothing on it . Now mine you this guy is not a dealer mechine so he has the time to see it.So looks ,as if i will tackle it my self!<br /><br /> Which main bearing is he talking about? Before he installed the lower unit, the motor never made this noise. This leads me to think that the place the drive shaft slides into (at the head)is worn? Can this be replaced easy? Can a average joe like me tackle this with a shop manual of the motor? <br />What do yall think is the problem? Would i have to tear the whole motor apart?<br /><br /> please help rcobb

 

[andrewkafp]

Re: 1973 20hp merc

I think the driveshaft slides into the end of the crankshaft. It is probably more likely that the drive shaft splines are worn rather than the crankshaft. (Hope so anyway). If the bearing is worn, you need to remove the powerhead. Once you have it off, you can assess the amount of wear and go from there.<br />"Before he installed the lower unit, the motor never made this noise"<br />I don't quite understand how you could have run the motor without the L/U as it contains the water pickup and exhaust.

 

[alcan]

Re: 1973 20hp merc

Hi Ryan<br />There could be a number of thing wrong with your motor and there probably is. As far as the average Joe fixing motors goes. Sure why not. I think most folks can do most anything they set their mind to. A good place to start is the library. Read up on outboards and outboard repair. Then you may want to invest in a manual that covers your motor before you begin work. This is sort of a win-win deal here. If you can make the repairs you will end up with a good motor and some knowlage. If not you will have the knowlage and some spare parts to trade or use on your next project. Either way your going to have fun.

 

[ryanc]

Re: 1973 20hp merc

Orginally I had taken the motor to another mechanic with the complaint of no top end speed, when I got the motor back the foot was blown out and the gears were missing. After shopping for three years I found a foot with drive shaft intact and took it to this mechanic. He inspected the splines and said they were fine. He put a new seal in foot and rebilut carb then we took it for a spin. It ran really fast for a few minutes then again full throttle it ran only below planeing speed for boat. I returned the motor to the guy complaining that the noise he said was a bearing problem was not there prior to him connecting foot and drive shaft. Anyway it cost us $200 bucks. I took the motor back for him to look at but he was only in to doing quick jobs during the season and told me I would have to wait till winter. so, it is winter.<br /><br /> It is hard to locate the noise, the boat runs fast with one person load but three people and it won't plane. I had told this mechanic before putting in the drive shaft to make sure that the splines were fitting tight and to inspect upper splines where driveshaft connects. He said this was fine. Now the story is something about bearings??? I don't believe he inspected the upper splines before connecting drive shaft. I believe the other mechanic did something possibly over reving the engine and then the foot gears blew out of the casing of the old foot, more than likely this torqued the upper drive shaft and probably lost a splie or two. I don't know because the original mechanic dissapeared and a year later I got the motor back with no lower foot ecept blown casing and no drive shaft. I am about ready to throw it in the river!!<br /><br /> Anyway, it doesn't look like this guy is going to work on it though he says he knows mercury's really well. So, I am back to square one and can't find a decent mechanic or atleast one who isn't a shark out for a quick kill. Any thoughts would be appreciated, thanks

 

[ryanc]

Re: 1973 20hp merc

Unicorn, after initially receiving the motor back with out the driveshaft and with a blown casing lower unit without gears I started motor up just to see if it still would crank, ran it for maybe 15 seconds and checked throttle range as well. the motor ran strong and cranked up easily, the carb seemed to work perfectly in its throttling.

 

[ryanc]

Re: 1973 20hp merc

i still need some help here with the mercury<br /><br /> help please ryanc

 

[ryanc]

Re: 1973 20hp merc

If anyone could please read my post and tell me some info this would be nice... I hope the guy will do the work though. rcobb