Mercury 8hp Seized NEED ADVICE!!

[cjp]

I am new to this site and need some help or advice! I bought a used 1985 Mercury 8hp motor that appeared to be in good condition and used it one time with no problems whatsoever. I took it out the second time and it started fine and quit running and appears to have seized up! I had good clean gas in the tank and was using Mercury oil mixed 50:1. I talked with a local Mercury dealer and he said it wasn't worth fixing!? My wife and I have two young boys who like to fish and we can't afford a new motor! I am mechanically inclinded to a point and I am just looking for some advice. I thought maybe someone out there could help me. I removed the rewind assembly and the flywheel will not turn. Any help would be appreciated!!

 

[smplesoft]

Re: Mercury 8hp Seized NEED ADVICE!!

Do you have the serial number? Mercury part numbers and diagrams are listed by serial number ranges. However, it sounds like the lower unit possible locked up. This doesnt mean its not fixable but repairing a lower unit can be costly. Did you change the lower unit gear lube before using this engine?

 

[emckelvy]

Re: Mercury 8hp Seized NEED ADVICE!!

These motors have a starter interlock that locks the recoil rope up tighter than a drum if the motor is in gear. If this interlock is out of adjustment or malfunctioning you may think it's seized when it's not.

Have you tried to move the flywheel with your hands? If you can't get hold of enough of it, remove the starter housing and then try it.

The other suggestion is a good one, too. Other than the bolts that hold the lower unit on, there's a shift linkage at the top, to one side of the carb. The locking device pulls up then out to one side to disengage the shift shaft.

After pulling the lower unit, you'll be able to isolate the problem. If the powerhead is seized up, you'd probably be better off finding another motor if you can't locate a good powerhead on eBay.

HTH & G'luck............ed

 

[sschefer]

Re: Mercury 8hp Seized NEED ADVICE!!

Sorry to hear about your problem. The first thing you want to do is remove the spark plug(s). Since you already removed the starter recoil unit and have a bare flywheel the second step is done.
The third step is to put the engine in neutral, (only after you've removed the spark plug), and try to turn the prop. It should turn freely if the lower unit is not damaged. If it doesn't then you're looking at replacing the lower unit. If it turns freely it doesn't mean your out of the woods but it's less likely to be a lower unit problem.

If you don't have a manual other than an owners manual, now would be a good time to go get one. Once armed with a manual, your first step will be to remove the lower unit.

Once it's off then use a socket and a breaker bar on the flywheel nut and try to turn the engine in a clockwise direction. This isn't a muscle man contest, if it gives you any resistance at all, stop, you have an internal problem.
An engine that old with the plug out should turn easily by hand.

I think you'll be suprised how easy they are to work on and how realtively inexpensive the internal engine parts are. It's the labor that will kill you if you take it to a shop.

 

[dkonrai]

Re: Mercury 8hp Seized NEED ADVICE!!

i just unseized a 15hp last night. i pulled the plugs, then filled the cylinders with some liquid wrench and premix oil. let sit overnight, and today the motor was spinning smoothly. worth a shot and you dont have to take the engine apart.

 

[Laddies]

Re: Mercury 8hp Seized NEED ADVICE!!

Anytme a engine freezes up, after making sure it's not a starter problem the next step is to remove the lower unit to make sure it's not the pinion bearing thats setup and holding the engine. Turning the prop shaft proves nothing.

 

[cjp]

Re: Mercury 8hp Seized NEED ADVICE!!

I was kind of thinking that it could possibly be the lower unit as well and looking at some of the feedback I have recieved it sounds like I should get a service manual and seperate the power head from the lower unit! Thanks so much for your help!

 

[cjp]

Re: Mercury 8hp Seized NEED ADVICE!!

To all. I have removed the starter assembly, plugs (plugs look normal), checked the starter interlock and it is not interfering, and in neutral the prop does spin freely but the flywheel still does not move. I did not put any oil in the the cylinders yet but could try that yet to. Could it still possibly be the pinion bearing then? It sounds like what I need to do is remove the lower unit from the powerhead to really isolate the problem. I guess its time to get a service manual! Thanks for all of your help! This site is wonderful!

 

[Laddies]

Re: Mercury 8hp Seized NEED ADVICE!!

Yes, the pinion bearings commonly seize from lack of lube and set engines up.

 

[cjp]

Re: Mercury 8hp Seized NEED ADVICE!!

Well, to all of you that have been helping me I thank you. I ended up tearing into the 8hp motor and tore it completely down and discoved that one of the bolts holding the connecting rod onto the crank somehow loosened up and let the split bearing come apart! It didn't seem to damage the cylinder bore or the piston itself, but two of the rollers from the bearing ended up above the piston in the combustion chamber! I am curious to how they got up there without damaging the bore or piston? Anyway, I need help trying to find parts for this motor! I have been looking online and cannot find individual bearings and what I have seen is I would have to buy a kit consiting of crank, rods, pistons, etc. and that was $450.00. I will also need a few new gaskets for sure.

The serial # on the motor is A126633 and the model # is 1010W. It was made in 1985.

Thank you so much

 

[Laddies]

Re: Mercury 8hp Seized NEED ADVICE!!

Here's a link for parts, you need your serial number to get the right parts.
http://www.mercruiserparts.com/selectSerailRange.asp?doc_nbr=15

 

[cjp]

Re: Mercury 8hp Seized NEED ADVICE!!

Thank you for your help!!!!!! Parts are ordered and on there way!!!!!!!!!

 

[sschefer]

Re: Mercury 8hp Seized NEED ADVICE!!

Anytme a engine freezes up, after making sure it's not a starter problem the next step is to remove the lower unit to make sure it's not the pinion bearing thats setup and holding the engine. Turning the prop shaft proves nothing.

I completely agree with you which is why I recommended removing the lower unit after the initial check.