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1965 vs 1970 50 horse

bill_w

bill_w

Advanced Contributor
I've got a 65 50 horse, with a great powerhead, but a trashed lower end. Can I transplant the old powerhead onto a 1970 lower unit? I can get the 1970 for next to nothing, but I don't want to buy it and find out I've got 200 lbs of aluminium thats no good to me. Have enough old junk as it is.
Thanks for any advice
Bill
 
Not easily. The water inlet to the block is very different. It can be done--I've done it--but you'll need to make an adapter.

Jeff
 
Well, what the heck...I bought the 1970...I guess I'll give it a try, and see how things fit (or don't). If it doesn't work, I'll have lots of old 50 hp Merc parts for sale, the 1965, a 1968, and now the 1970.
 
OK, got the old girl back together. When will I learn to closely look at stuff I buy?? The siezed 1970 I bought for the gearcase looked good, untill I actually opened the gearcase. Can you spell RUST?? I should have tried the flywheel after I took the gear case off, it might not be the block that was siezed. Anyways, I got the 65 gearcase put back together, and now I have a reverse gear again, and the reverse cam lock now works (that is actually all I salvaged, was the cam lock). The whole problem with the no reverse was the cover nut being broken/not tight. The 70 unit will fit the 65, the only difference is the position of the shift rod cover/seal. On the 70, it screws into the casting at the top of the casing, on the 65 its recessed into the casting. By unscrewing the cover seal from the 70, stacking it on top of the 65 seal, and a couple of washers, it's now at the same height above the gearcase as the 1970. This let me use the reverse cam lock from the 70, and everything now works.

Question? Did Merc sand cast the gearcases?? I thought my old gearcase had a split from freezing, but when I started to clean it out, it was a big pocket of sand, sandwiched in the aluminium, right at the front of the gearcase, under the antiventilation plate. I just filled it in with JB Weld. It was big, about 1 1/2" long, 1/2" wide, and about 1/2" deep. It didn't lead to the inside of the case, I dremmeled it out to good metal on all all three sides, and there was aluminium on top of it, until I started at it with a screwdriver.
 
Ok, so maybe a small split or defect, that filled with sand/silt, and just got worse. Anyways, not an issue, it holds oil. Next question...this engine is not charging..how do I check the rectifier? And can I test the input to the rectifier, to see if there is anything getting to it? Sometime in the past, the engine had a pretty serious electrical problem, a lot of the wire insulation shows overheating, blistering, etc. The PO wired in a 5 amp fuse to the (I think)output side of the rectifier.
 
Let it idle and put a volt meter (on AC) across the two yellow wires coming out of the stator. If you see 13 or so volts, replace the rectifier. If you see no volts (or battery volts, perhaps) then the stator is shot.

Jeff

PS: I might have a good stator if you need it.
 
I'll check the stator output this weekend (motor's 100 miles away). I will go thru the parts listings here, but maybe you know Jeff. I do have a 68 and 70 powerhead, plus another stator in a box of parts that came with the 65. Will either the 68 or 70 stator fit the 65?

thanks, Bill
 
OK, searching thru parts listings here...the 65 stator is 398-2171. For the 68 and 70, its 398-2996. Mecr doesn't give "replaced by" part no's, like OMC does, so the newer ones may fit, if I have to change it. Any way of testing them without the motor running?
 
OK, will do. BTW Jeff, I finally put one of your coils into my 77 20 hp. Runs like a dream now, and the mechanic said it wasn't worth fixing!!
 
Good for you!

With new OBs costing thousands of dollars, it's usually worth fixing up the old ones. My customers certainly think so, for they filled my shop with old Mercs again last winter.

Jeff
 
I don't know about you, but I find the older ones a lot easier to work on. Don't have to be a computer tech to find a bad widgit that costs $700 to replace. I've been building up a collection of older stuff, just found out about 4 or 5 more oldies I'll likely get for cheap. At least one is an old white Merc. Gonna have to build a bigger shop.
 
Yeah, gonna have to sell some stuff....like this 50 Merc. Boat that its on is junk..took it out sunday nite for the first time. Transom is so rotten its bending. Oh well, got it up and running not too bad, carbs need to be done. The stator has continuity, about 1.3 ohms resistance. At idle, its about 3-4 volts ac, up to about 13 volts at a fast idle. Changed out the rectifier with one from the 70, and am getting really erratic DC voltage, 2 to more than 20, and it keeps switching from pos to neg. So, I guess that rectifier is no good? From what I can see, I do have 2 more stators that will fit, one from the 68, and one in a parts box. May just sell it as is, and include the parts. I have a question about distributors. How do you change the cap and rotor, without pulling the whole unit? Another question..did Merc make 50's without charging systems? The 1970 has no stator, no rectifier, and doesn't look like it ever had one. The Bat + wire just dead ends at the terminal block. Oh yeah..this is the motor that was siezed. It wasn't the powerhead, it was the gear case that was frozen.
 
Opps..re-read your earlier notes..should be putting out about 13 Vac at idle. So, I guess the stator is gone.
 
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