65-66 Merc 650

[Poopdeck]

So I bought a 65hp Merc 650 3cyl for $50. The engine is complete but I have no wiring or controls to go with it. The overall condition of the engine is really good considering it's age but it does have the expected wire corrosion problems. My intent is to replace the 48hp Johnson on my pontoon with this engine if I can make it dependable. Here is where I start asking questions...

The serial number places the engine in the late 65 to early 66 year model and that's the best I can figure out. It's amazing at how little information there is on these engines. I have no history of the engine other than the kid I bought it from said he got it from an older couple on a boat he bought. It's supposed to be in running order per the old couple but the kid never fired it and replaced it with one he had from another boat. Believe the story if you will but that's what I was told. The truth is I have no idea how long it's been since it was ran or why it was removed. I will say this though, the rear supports for the top half of the cowl are broken at the bottom by the bolts which leads me to believe it was either hit from the side or fell over while off the transom. I read the post here about waking a sleeping outboard and that is the guide I will use to check this thing out but where do I start? I don't want to sink a lot of money into an engine that may or may not be worth saving. I have ordered a user's manual for the engine but it has not come in yet.

Can I check compression turning the engine by hand? What else should I look for that would be a reason to quit now?

I have turned the prop by hand but that's it. Either it's in neutral or the drive shaft has broken off. Sorry for the long post but I have more questions than I can remember to ask at this point. I'm pretty mechanically inclined but outboards are an alien species to me, antique outboards even more so.

 

[GA_Boater]

What is the serial number? A 3 cylinder Merc 650 in 1965 or 1966? 3 cylinder 650's began in 1972.

No, you can't do a compression check by turning the flywheel by hand. You can cheat the missing controls and use the electric starter. Does this one also have a pull start?

 

[Poopdeck]

The serial number is 1891529. No pull starter. I'll be honest, I haven't had the cover off yet so it could very well be a 4cyl.

 

[GA_Boater]

1966 4 cylinder. Count the sparks plugs again.

 

[GA_Boater]

Take the covers off and look inside. The wiring may not be all that bad if you're lucky.

And you can manually shift to see if you have F-N-R.

 

[Poopdeck]

LOL, like I said, I haven't had the cover off. The center band is off and I only saw 3 plug wires. That's what I get for assuming.

 

[racerone]

So it is a 4 cylinder motor.-------Certainly a much better design than the early 3 cylinder !-----Bonus, that motor uses the elegantly simple / reliable magneto.-----No battery required to make sparks.-----Just work carefully on that magnet as the parts ( if needed ) are a bit spendy.-----Compression test / inspection should be done before spending any coins on this motor.----Could be a good one.

 

[Poopdeck]

So it is a 4 cylinder motor.-------Certainly a much better design than the early 3 cylinder !-----Bonus, that motor uses the elegantly simple / reliable magneto.-----No battery required to make sparks.-----Just work carefully on that magnet as the parts ( if needed ) are a bit spendy.-----Compression test / inspection should be done before spending any coins on this motor.----Could be a good one.

The magneto is good to know. I have some experience with 60s and 70s motorcycle engines so I'm hoping the outboard won't be that different. I plan to pull the plugs and check the compression today after work. I guess we will see if I got a good deal on an outboard or a good deal on a parts engine. At $50 I couldn't pass it up. It's bound to be worth that in scrap.

 

[racerone]

One of the keys on these is the fact that they did not use stainless shafts on the lower unit.---Resulted in many lost lower units.---------Replace the impeller before the official launch of the boat.-----I have one or 2 of these motors myself.

 

[Tassie 1]

Another vote for taking the cover/s off ( all three parts )
you have to do it eventually,
might as well do it now lol

l also have one though mine is a 50, same 4 cyl block,
paid $50 ( aud ) too
though l just bought mine as a non running wall hangar...we did have a running 65hp 12 yrs or so ago,

when you eventually get around to taking the cover off you'll see a rubber timing belt and rubber fuel lines,
they could well be 53 or 54 years old,
in other words, brittle and could break or crack while your looking at them, on the inside as well,

my brittle timing belt broke after hand turning the flywheel

replacing them all will cost more than $50, l think the timing belt alone is around $35-38 US,

then you have to find the remote and wiring loom, more $
it also has olden day funny looking carbs on it...

don't order the impellar untill you've actually got the lower unit off, the mild steel drive shafts rust and sometimes corrode into the crank and major surgery is needed to " remove " them, as racerone points out,

"made reliable"?
don't know about that,
sometimes just getting these old girls to fire up could be enough to kill them for good,
energy spikes etc through old wiring that's been sitting on a dusty shelf for decades etc,

l like fiddling and fondling old outboards but actually using one on the water other than on " Old Boat Festival" day in the local pond ( small, very ) is dicey
thinking about replacing a running motor with one is even moreso, unless you like the idea of the tow of shame,
jmho

 

[racerone]

Those old magnetos are very good / reliable.------Of course an owner has to learn how to do the annual maintenance on these things.-----New technology is great for folks with no budget concerns of any kind !!-----The 4 cylinder 65 and 4 cylinder 50 HP are NOT the same block / displacement either.

 

[Tassie 1]

l also have one though mine is a 50, same 4 cyl block,

l clearly need to modify this statement to " looks almost the same as the 65hp block" lol

l blame the tryany of time, old age and a feeble mind...
also not having the required $ to update me coke bottle glasses as often as l should

 

[jimmbo]

the 1963, 64, 65, and 66
Rated RPM 5200
2 7/8" bore
2.3" Stroke
60 cubic inch displacement
Sparkplug J4J

the 1967 - 71
WOT RPM 4800 - 5300
Bore 2 15/16"
Stroke 2.3"
62.4 cubic inch displacement

 

[Poopdeck]

Ok. I took off the top cover, pulled the plugs and hooked up the compression tester only to find that the starter wouldn't turn. I took it off and took it apart. Cleaned the starter good and checked the windings, brushes, and commutater. It had some rust and crud in there but she's all clean now. The engine will turn over by hand and feels smooth.

As I imagined, the wiring is crap. Most of the small wires had almost no insulation. Looks like I'll be making a harness.

 

[jimmbo]

Before you go and spend a bunch of Time and Money making a new Harness, find out if the engine even has compression.

 

[GA_Boater]

Since the wiring is a mess, which isn't unusual for old Merc, hook a battery up to the solenoid positive stud and to the ground stud by the starter using jumper cables. If the starter is working after the clean up, tap a jumper wire from the positive solenoid large stud to the small solenoid stud with the white wire. The motor should crank.

If it cranks, pull all the plugs, hook up the compression gauge and start testing each of the cylinders. Don't worry about the wiring until the compression is checked.

 

[racerone]

Using the old fashioned rope on the flywheel will get the numbers on a compression check.

 

[DeepCMark58A]

I also would not spend the money on a pre made wire harness, these are pretty simple motors electrically and changing out individual wires is not that difficult. I use THHN wire, oil and gas resistant. I have always wondered if the ozone produced is not part of wire insulation failing.

 

[racerone]

?----Would the ozone not disappear via the carburetors ?

 

[Poopdeck]

Before you go and spend a bunch of Time and Money making a new Harness, find out if the engine even has compression.

That's the plan. I can't get back to the engine until this afternoon though.

I have a couple of questions though.

1. What is supposed to go on the bracket below the starter? There is a "C" shaped, aluminum bracket of some sort bolted to the block below the starter but there is nothing attached to it.

2. How does the bottom cover come off? I noticed it has a short collar on the bottom held on by a few screws but once that is off, how does the actual bottom cowl section come off? The swivel mount in the front won't let it drop down any more.

I have more time than money so I will definitely be making a harness over buying one. I've made a few over the years with good results. Does anyone have any ideas on a replacement for the plug that comes through the cowl? Since I don't have the boat side and there is a broken prong on the engine side I thought maybe I would just do away with the whole thing and try something else. Maybe a 7 pin trailer plug? I thought about roping the flywheel but I couldn't find anything at the shop that was suitable for the task, maybe I'll find something at home before I go today.