TOPIC: 1965 90HP

Thinking of buying a 1965 90HP. The issues are that the top two cylinders have low compression 30-40 lbs. (the other 4 are 120), It has a newer( later than 1965 unknown year) lower unit, and the controls are incomplete. I most likely would not be able to do the work myself should I buy this motor? Looks to have been used in fresh water fairly clean and turns over.

If you can get it cheep go for it.

I got my 1965 900 merc in great shape on ebay 2 years ago for 335 bucks not running. It's a short shaft and in excellent condition and did not take much to get running. I figure ebay brings some of the top values with a wide variaty of bidders.

One with compression issues should bring considerably less than that. The lower unit if in great shape can be sold for 200 if you get it and decide to scrap it. That would be my top dollar.

Otherwise mine is a great motor. I tore it down for good measure and replaced bearings and some chipped reed valves.

The hardest thing about this motor and other 6's before it is getting the two sets of points set correctly. If they are off it will not run worth a crap.

This is the first year of the "Quieter" motors, completely redesigned with the control cables entering the front of the motor and hook up inside instead of outside like the early motors did.

I do think they are quieter!

Conrad

I have a 66 950. You have a 90 cu in block which is very easy to find pistons and rings for. It sounds like a bad impellor did the motor in where top two cyls are bad. The fact that it is the top two may indicate it was run for a while with low cooling so hopefully the bores are not scored too bad or the top reed cage didn't get damaged at the crank I.D. I have not seen many oversize pistons for the 90 cu in motors but lots of standard size ones. As a fix, if needed, you could rebore to the 1100 pistons as they are slightly bigger, you can still find these, but not common. but, it would be best to find a decent block only needing honing if it turns out yours needs more.
The other thing is to Conrads comment about the dual point system. Becasue of the inner cowl support configuration you could easily convert this motor to Thunderbolt ignition, i think this is a major plus. You would need the distributor, switchbox, coil and front inner cowl support to do the conversion. Some rewiring would be needed but all pretty straight forward.
I like the 65/66 inline 6's becasue the outside trim is similar to the earlier motors but they are quieter and can run the improved ignition system. The 66 had a hybrid thunderbolt using the same dual points to trigger the switchbox rather than the 67 up electronic trigger. I kept the dual point trigger for originality but consider up grading when I do normal maintenance is done on the points. If you get the motor and want to do the conversion look for 67 up parts.
The motor needs work and should be priced accordingly.
My two cents,
Randy

Went and looked at the motor. Did a compression check; the lower 5 cylinders were 130 plus. Top cylinder was 40; after spraying some defogger in spark plug hole and cranking over it came up to 80. Did not see any signs of over heating but who knows.

It is a short shaft with kit to make it a long shaft. Lower unit looks fairly new. Mid section has been spray painted over some corrosion. On mid section about midway up on starboard side is a hole about 1/4" wide and 1" long. The hole is at an angle and looks like under the new spray paint corrosion or heat or something was going on around the hole. Does not look like a factory hole more like something popped out or was drilled in, strange. The cover and wrap is in good condition with a few scratches.

It comes with two face plates, a brass three Blade propeller, cable set for this motor plus NOS cable set for 1966 motor($300. from old merc guy), controls w/key, two extra starters (one new one rebuilt), how to repair CD, owners manual. Home made stand.

All well under $200.

I need a long shaft not crazy about the looks of the conversion set up. Need to decide.

the hole was most likely put in there to help remove a drive shaft that was rusted in.an air impact gun pounding on the shaft breaks it loose.

Steve I sent you an w-mail not long ago.
just got this pc back up after a few months
Call me when you get a chance
Jim

Depending on where you live there are at least two guys that would have a long shaft,the SS are getting harder to find from what I read.So there may be some classic guys looking for that boot allowing you to break even,maybe even swap it.Dr Frankenmerc on the West Side and Paradise Boat works on the East Side are the two people that I would talk to.I was recently in Paradise's wharehouse and it is loaded with parts from that vintage.Someone else may chime in here with other sources.Both of these gentleman are 'partners' on this site as well as Nicklecityclassics so I feel safe in recomending them.You may get lucky and let that cylinder soak in Marvel Mystery oil for a while allowing the rings to free up a bit more.I may also add to 63g3's comment about the possible reason for bad compression.I have read and I am no Merc guru, so take it for what it's worth.That if the top carb in your case, is running lean that will also cause lack of lubrication and possible piston failure.

I ended up buying the motor. If anyone is interested in trading a short mid for a long mid let me know. It also came with two additional starters, and an extra face plate.

just sent you an e-mail