1970 80hp, what should I do ??? Rebuild or buy another. -UPDATE-

[Moody Blue]

I've got a 1970 Merc 80hp that has been partially disassembled by previous owner. All parts appear to be there from what I can see. Motor was not running so he started to take it apart, but that was 20 yrs ago. It has set that way ever since. Motor turns over freely but I can't do a compression test because the exhaust covers are off.

Is it possible to resurrect this old machine or should I be looking at something newer in running condition? I have no idea what may be wrong with the motor other than it wouldn't start 20 yrs ago.

My concern is that parts may not be available. Don't want to start sinking money into this only to find out I can't get a needed part.

Is there a way of testing the stator, switchbox and ignition coil separately?

What would YOU do in my situation?

Thanks in advance for your help.

 

[emckelvy]

Re: 1970 80hp, what should I do ??? Rebuild or buy another.

Re: 1970 80hp, what should I do ??? Rebuild or buy another.

Note that having the exhaust covers off has nothing to do with the ability to take a compression check. However, it does give you a real good 'window' into the condition of the pistons/rings. Inspect with a strong light, if you see stuck rings/scuffed pistons/scored cylinders you know you've got your work cut out for you. If it looks clean, I'd take a compression check, and depending on the results, not even take it down for a rebuild. I would replace the upper and lower crankshaft seals. The end caps can be removed without splitting the case and crank seals are a very common issue with these (especially the lower ones).

Regarding parts availability, all the consumables for this motor (pistons, rings, bearings, gaskets) are still available as there was a lot of parts interchange up to the late 80's. Plus a KaJillion used parts on eBay!

The stator has just 2 wires and can be checked with an ohmmeter. As long as the stator has a fairly low-value resistance and neither lead has continuity to ground, it's likely OK.

The ign can be fired-off without running the motor. See this thread for a good troubleshooting writeup and other tips:

http://forums.iboats.com/showthread.php?t=209149

If you connect 12V to the red terminal on the side of the CDI power pack and the white terminal on the same side, and all components are good, you'll get fire out the coil when you spin the distributor.

Note if things are still somewhat together (i.e. powerhead still bolted up, distributor installed, etc.), just hook a control box up along with a battery and go for it.

If the distributor is loose from the motor, you can still fire off the ign as I described previously, just make sure the (3) wires off the distributor are properly connected to the CDI power pack, and connect a separate ground wire from the metal body of the distributor to the metal case of the CDI pack. Same thing with the coil if it's loose. All the parts have to have a common ground to work correctly.

If you get no spark out the coil when you spin the distributor, disconnect it and troubleshoot per the linked writeup.

If you determine the dist is bad (which is what I'm betting on, a bad trigger assy), the entire body minus rotor/bearings/chopper/moveable collar/etc is one piece and is changed as a unit. Pretty $$pendy and hopefully your other 4-cyl has a good one.

Just a start, have at it and let us know what you find.........ed

 

[Moody Blue]

Re: 1970 80hp, what should I do ??? Rebuild or buy another.

Re: 1970 80hp, what should I do ??? Rebuild or buy another.

Thats a lot of great advice. I am never disappointed on this site.

This is my project for the weekend. Crossing my fingers that the distributor is not bad. I'm really looking forward to getting this motor running again. It looks in fantastic condition. Also, the lower unit was rebuilt just before the motor quit so thats a plus.

Will let you know how it goes.

 

[Moody Blue]

Re: 1970 80hp, what should I do ??? Rebuild or buy another. -UPDATE-

Well good news and bad I think.

Tested ignition system per your directions and as described in the link in your previous post. Stator tests good. Tested coil and power pack separately and got nice strong spark. Reinstalled the distributor cap, removed the timing belt and spun the distributor by hand and again, nice strong spark. I am happy. Ignition system is good.

Re-installed the flywheel and starter and did compression test. Cyl 1-3 tested at 135-150psi BUT cyl 4 only 85PSI. I am not happy. Pulled the lower exhaust cover and bad news. Lots of corrosion. Looks like water has gotten in there at some point. Everything spins freely but obviously something is not right.

I've attached (I hope) a couple photos of the lower exhaust port. What would cause this and is it repairable?

Please tell me its easy to fix.

 

[Scaaty]

Re: 1970 80hp, what should I do ??? Rebuild or buy another. -UPDATE-

Well, its for sure got water intrusion problems, and could be any number of things.
Maybe someone else will come along a good suggestion, but if it was mine (I love the old mercs, own a 135), I'd sell the parts, find something else.
That motor has to come apart...

 

[emckelvy]

Re: 1970 80hp, what should I do ??? Rebuild or buy another. -UPDATE-

Actually that's the intake side. Bad Mojo for sure! Probably sucked in water from either the lower crankcase seals, or a problem with the exhaust baffle or inner port cover. But Scaaty's right, has to come apart for an inspection. You might try pulling the lower bearing cap to see if the seals are bad.

The cap is held on with 3 bolts (be careful if they're stuck, you'll need to use heat from a propane or MAPP torch to avoid breaking the bolts). You may also want to loosen the 2 very bottom opposite-side bolts on the crankcase halves to help take a bit of tension off the cap. Usually the cap will slide out with not a lot of force once you get it started.

If you see a ton of rust around the crankshaft lower ball bearing, it's likely the crank is shot. More parts needed, DOH!

Maybe the 85HP is in better shape???????

 

[Moody Blue]

Re: 1970 80hp, what should I do ??? Rebuild or buy another. -UPDATE-

Well I got it completely apart without many problems. Thought it would be tougher after 38 years. Only issue was that one of the powerhead studs was seized inside the intermediate plate that holds the exhaust tube and shift rod. Ended up pulling the whole assy out of the lower leg.

Anyway from what I could see, the lower seal was defective allowing water to enter. Could not see any defect in any of the gasket faces as it came apart. All the damage was isolated to the lower seal housing and bearing.

Rings in piston #4 are stuck but not corroded. Piston looks fine other than minor rust staining. Much to my surprise, the cylinder wall looks none the worse for wear. After cleaning everything up, it looks no different than the other three cylinders. No corrosion or pitting at all.

There was a fair bit of sludgy rust deposit ontop of the lower seal housing and inside it as well. The lower bearing is shot but still turns. Can't get the bearing off the crank (yet), but the end of the crank that sits inside the seal housing looks fine. Once I get that bearing off I'll have the whole picture.

So what do you think? Have the cylinders honed and install all new stock sized rings? Replace the lower bearing and all new seals? Could I be so lucky?

I've read on another post that it is recommended to install three seals in the lower housing.

Opinions please.

 

[emckelvy]

Re: 1970 80hp, what should I do ??? Rebuild or buy another. -UPDATE-

Better check the conn rods/bearings/crank surfaces. Reeds are showing rust so water got all the way up there. I'd be real worried about #4 & #3.

If they check out, likely you could use a "dingleball" style glaze-buster and re-ring with standard size.

If you're going to re-use #4 piston/rod assy, be sure to check the wrist pin bearings and conn rod big end for rust.

The wrist pin just drives out of the piston, if real tight heat up with a hot air gun or a few seconds of propane torch on the top of the piston.

If it looks in good shape, reassemble using a bit of Vaseline to hold the needle bearings in place, and replace any wrist pin clips removed.

Use 1 drop of red Loctite on any disturbed conn rod bolt, in the area where nut engages bolt.

See my other post for tips on R&R of the lower crankshaft ball bearing.....ed

 

[Moody Blue]

Re: 1970 80hp, what should I do ??? Rebuild or buy another. -UPDATE-

Ed thanks so much for your help.

Will pull the piston and conrod off the crank tomorrow and take a look. A question thought.

Do I need to remove the piston from conrod first before I can remove the bolts from the conrod cap?

The conrod bearing cap is bolted from the piston side and looks difficult to get too with the piston in place.

Rod

 

[Moody Blue]

Re: 1970 80hp, what should I do ??? Rebuild or buy another. -UPDATE-

Ed you were right on the money. Removed the conrods from the crank and the the pistons from the conrods. Doesn't look good from what I can see. I created a new topic with photos.

Looks like I'll be parting out this motor unless you know of a miracle cure.