1970-72 merc 800? 80 hp-sn#2885673

[ovnic1234]

1970-72 merc 800? Is the correct year according to the serial number. I looked it up on oldmerc.com.

I bought a junk boat specifically for a trailer. On it was this motor minus the lower unit. Where the transom meets the hull there is a large crack as if they hit something. The guy I bought it from knew nothing of the history. He bought it off some neighbor for nothing. All he wanted was some side rollers for his trailer. The controls, trolling motor, and battery were still in it. I am hoping something went wrong with the LU and it got parked and forgotten about.

The motor is not locked up. Is it possible to do a compression check, in it's current state. I hate to invest in a lower unit, if the powerhead is shot, but don't wish to break it down for parts/discard, if there's a chance of making it work.

Any pointers on how to lubricate and test?

Thanks, My limited experience is mostly with low hp evinrude/johnsons 50's and 60's, but am fairly mechanically inclined and have some smart folks to help.

 

[jerryjerry05]

Re: 1970-72 merc 800? 80 hp-sn#2885673

Yea you can do a comp test without the lower.Just remove the plugs.Hook up a jumper wire then hook up the tester and turn it over.J

 

[ovnic1234]

Re: 1970-72 merc 800? 80 hp-sn#2885673

Very simple, sounds good. Will oil up each cylinder prior.

I hope it's a winner.

Thanks,

 

[Moody Blue]

Re: 1970-72 merc 800? 80 hp-sn#2885673

Yea you can do a comp test without the lower.Just remove the plugs.Hook up a jumper wire then hook up the tester and turn it over.J

Be sure to ground the plugs before cranking it over. You don't want the ignition system trying to fire the plugs hanging in mid-air. If you use a remote start switch then just leave the ignition key off and don't worry about the plugs. The ignition system is disabled if the key is off.

I have the same motor, a '71 model year. Most likely you will need to rewire or replace the internal wire harness. All the old Mercs had problems with the insulation crumbling and falling off the wires.

Good luck with the compression test. Use a fully charged battery to obtain accurate results.

 

[ovnic1234]

Re: 1970-72 merc 800? 80 hp-sn#2885673

Well, I couldn't find the key. Not unusual for me. So I oiled up the cylinders, and wrapped a rope. Pulled five times on each cylinder. Here are the results:

#1 120 lbs
#2 140 lbs
#3 140 lbs
#4 140 lbs

Boo Hoo,

Any ideas? Tear it down I assume. This is an unexpected project. I'm wondering why this happens. Why just #1.

Curious about the potential cost.

Thanks, Paul

 

[Moody Blue]

Re: 1970-72 merc 800? 80 hp-sn#2885673

IMO, I would run it as is. It's a 40 yr old motor and the numbers you are giving look pretty good. General rule of thumb is to ideally have all cyl's within 10%. You are just outside this range.

 

[Huron Angler]

Re: 1970-72 merc 800? 80 hp-sn#2885673

I have not tested the compression on my '71 Merc 800, but I ran it all summer and I'd be willing to bet that when I do check it will be even worse than what you've got there.

Mine has written with a sharpie compression numbers on the engine block and one cylinder was lower as far back as 1985, similar to your figures.

I agree with Moody that you should run the motor. The compression may improve after letting her run for a bit.

Good luck with the new motor

 

[ovnic1234]

Re: 1970-72 merc 800? 80 hp-sn#2885673

I was a little impatient, and started tearing the motor down. I haven't made it to the core of the powerhead. i.e. pistons, block, etc... From your advice, I'll leave them be. There was some questionable wrenching done on the motor. Rounded over fastners, missing bolts. I don't care to leave any stone unturned. The ignition wires and wiring in general look toast and I think I have a new in box coil. The carbs I image need a good cleaning, if not a rebuild.

I documented the hell out of it with the camera, and I am going to order a specific manual for it. My experience lies mostly with 50-60's evinrude/johnson twins, so this is new territory.

I have a boat for this motor, which needs a new floor and stringers, so by spring I hope to bring both motor and boat up at the same time. This thread should reappear in the Winter sometime.

I was willing to pay 150 for a trailer, so this motor is a bonus. And it's nice to hear that it's not something that's only good for parts.

I like a tag line of one of the members of this forum, that I've seed in the restoration section, relating how his son makes the statement that if the boat they were working on would have been well made, they wouldn't have a have it at all. Not quite the same, but I would never have considered this project if it wasn't practically free. (150+$27 at the dump)

Thanks for responding, I failed english in high school, if that buys me any slack with the grammatically inclined.

 

[Huron Angler]

Re: 1970-72 merc 800? 80 hp-sn#2885673

Sounds good, I would love to see some photos as I have the same outboard.

I plan on rebuilding my two carbs this winter in the hopes that I can get her running 100%. So far only around 70% or so.

Good luck with it. Did you get the Mercury manual or seloc?


http://forums.iboats.com/showthread.php?t=296896

Also check out that link^^ it is a rebuild on a 80hp Mercury outboard that has helped me a bunch since it is very well documented with photos. EdC did a very nice job restoring his outboard down to the cowling paint.

 

[ovnic1234]

Re: 1970-72 merc 800? 80 hp-sn#2885673

I saw that thread, absolutely beautiful. Thanks for linking it on here, easier to find it later. Would like to think that I'll do that nice of a job, but on the cosmetic end it's doubtful. Mechanically, that level of finish is what I'm looking for. This motor is for a boat that l'll leave with my dad, so he and my mom (retired) and the grandkids can goof around in.

Brand loyal folks will either get a laugh or not like it one bit. But a Mercury motor is going on an Evinrude boat. It's a 1967 Sportsman, like the one from the James Bond movie "Thunderball" Split windshield, cool as hell.

Getting off subject, will post pictures and questions no doubt when this project gets rolling. Sometime when it gets to cold to do anything else but hide in the garage.

Take care all