Need help with the possible purchase of a 1975 85hp merc....

[Dadoftwo]

Ok, so here's the deal. I found a gorgeous boat in near mint condition with a similar condition motor. The motor has approximately 200 original hours on it. The powerhead is clean enough to eat off of, all wiring is pristine etc. The motor was used in a saltwater environment but was flushed after every use and was trailered its whole life.

The setup would be perfect for my wife and I (and 2 small kids) but I am concerned about the motor. The motor will be operating in NJ and we are currently afflicted with E10. Will the internals hold up with the ethanol? I tried doing a search and didn't really come up with anything that helps....also, is there anything I should watch out for?

I am a little snake bit with Merc motors. Had a 1985 75hp that never ran right no matter who I paid to fix it, a 225 optimax that had more alarms going off then one can count....the final was a 1987 Inline 6 115hp which I had Clams drive to NJ to rebuild (that I am happy to say is still running like a top almost 2 years later!).

Any help is greatly appreciated. Unfortunately we are on a very tight budget so a rebuild possibility is out. Need to get a good runner (I know, I know...its a crap shoot but still........).

 

[emckelvy]

Re: Need help with the possible purchase of a 1975 85hp merc....

Definitely a concern regarding salt useage. This motor is old enough to have needed the inner exhaust baffle replaced; if it looks like it's been done, you're probably OK. If the exhaust side looks like it's never been opened, it's definitely due.

This could be a bugger of a job since the powerhead has to come off to get at all the manifold bolts; and if the bolts have never been removed, they are probalby all salted up.

Quite a bit of labor (and possibly some Heli-Coils will need to be installed where bolts break) to get it apart. One way to get an idea of how difficult the repair would be is to lay a wrench upon a couple of the exhaust manifold cover bolts and see if they easily break loose. Be sure to tighten them back up if they do!

Good News is, while the powerhead's off, the other problem area with these motors can be addressed: the crankshaft lower seals. Quite common to see the seals bad, which leads to poor idling and ingestion of water. Easy to pull the bottom seal/bearing carrier and renew the seals, without having to split the crankcase open.

If this motor has the original lower unit, it probably has a mild steel driveshaft. These have a tendency (especially in salt) to rot around the drivehshaft seal area. So do pull the drain plug and check the gear oil for signs of water.

It's probably about a $100 bill for parts to fix this problem and service the pump while you're in there. If the corroded area on the driveshaft is not that bad, you can drive 2 speedi-sleeves (around $25 each) over the damaged area and this'll give the new seals a good surface to ride on.

Definitely take the boat out, see how it starts, idles, and runs at speed. If it runs like a Swiss Watch and idles well, it's probably OK internally. Shut it off and then fire it back up; it should start immediately, with barely a tap of the key, if it's in good tune (just like any Big Merc should!).

If you can get a compression check done, more's the better. Ideally, readings should be within 5 psi of each other, 10 psi at the most extreme. Any more than that and 9 times out of 10 there are ring/piston problems.

Anyway, hope this doesn't scare you away but at least you'll be armed with a bit of info to help you make a decision. If you do buy it, plan on servicing the water pump regardless of any other repairs needed. Unless you know it's just been done. Also give it a Seafoam treatment, to clean out any carbon deposits on the rings.

BTW if your Inline Six shows no ill effects from running on E10, the 4-cyl should be no different.

HTH........ed

 

[tashasdaddy]

Re: Need help with the possible purchase of a 1975 85hp merc....

what's the boat rated for, swap the motors. you know you have good one.

 

[Dadoftwo]

Re: Need help with the possible purchase of a 1975 85hp merc....

I wish it were that simple. The newer boat is rated for up to a 130, mine is up to a 70. 48 would be too little, the 85 would sink my skiff