Finally Had To Retire It

[racerone]

Well ---I would say that the motor is the 4 cylinder 75 HP model.---Easy to tell by carburetors.

 

[chris.olson]

I think he stickered it as a 60hp because it broke 60hp on the dyno. The decal companies are usually able to customize if you ask them

That's correct. Technically it's a 65 because it has the 62 cube powerhead. The 500 and 50 have a 44 cube powerhead. Due to differences in how they rated marine engines in years past I didn't expect it to make the 65hp it was originally called. I was pleasantly surprised to see 63 on the dyno. The original chrome faceplate was lost off it, but a newer plastic one fits it. When I went thru the powerhead, and restored the rest of the engine, the 60 decals off the newer 3-cylinder models happened to be readily available and they kinda fit. Those decals are the OEM Mercury part, not from an aftermarket decal maker.

Had to cut down the "Mercury" decal on the faceplate to fit. But the rest were a pretty good match.

So it became a 60. It's a healthy 60, and it looks dang good. Runs even better.

 

[Faztbullet]

The lower unit and prop appear to be a 44 cube

 

[chris.olson]

It has a gen II lower unit, 1.6 ratio with a spline shift shaft. That was replaced with a good used one before I got the outboard. The paint stick writing was still on it from where ever the previous owner got it from.

 

[Faztbullet]

Gen II is a Mercruiser and wont fit...easy way to id is to count splines of prop shaft or easier the the prop size. If its a 10 or 11 by XX pitch its a 44 cube.

 

[chris.olson]

Gen II is a Mercruiser and wont fit...easy way to id is to count splines of prop shaft or easier the the prop size. If its a 10 or 11 by XX pitch its a 44 cube.

It has a Solas prop on it, 13.5 x 13. Not sure of the number of the splines. I had the prop off to grease the output shaft splines when I pulled the lower unit to check the water pump, but didn't count them.

 

[Faztbullet]

If its a 13 diam its a 66 ci motor and 2:3:1 gear ratio

 

[chris.olson]

If its a 13 diam its a 66 ci motor and 2:3:1 gear ratio

When I had the powerhead apart to put reed blocks in it I pulled the pistons and rings to look them over and check the ring end gap. The bore was 2.938 and the stroke was 2.296. 15.5 cubes per hole.

The lower unit had paint stick markings on it, said it was 1.6 Merc 115hp. However, I just went out and put a piece of green tape on the prop. and turned the flywheel by hand. I got about 2 1/4 turns for one turn of the prop so it is indeed probably a 2.3. Whoever had marked it with a white paint stick didn't count it out very good. It was obviously a replacement lower unit that came off a Tower of Power, and the previous owner had painted the leg Caterpillar yellow. It does have a spline shift shaft, though, and not a square one like I've seen on some earlier Mercs. I call the ones with the spline shifter gen II because the earlier ones had to put the lower unit back on in forward gear. This one you put on in neutral because it has a neutral detent. It had no decals or markings on it, the driveshaft housing cover was missing, the faceplate on the engine cowling was missing, even the serial number plate is gone. But I got it for only $200.

 

[racerone]

I would say the engine is the 4 cylinder model 650 last marketed in 1971 rated at 65 HP.

 

[chris.olson]

I would say the engine is the 4 cylinder model 650 last marketed in 1971 rated at 65 HP.

I think it's a hybrid that has had various parts replaced on it with newer parts. It has a new stator and newer flywheel on it with Thunderbolt CDI ignition. I thought those older Mercs had a distributor, but maybe the 650 never did, not sure. The lower unit, I'm pretty sure, came off an inline-six Tower of Power. It has the plunger in the end of the driveshaft, I didn't think the older ones had that.

Regardless, these are some of the best engines Mercury ever built IMO. The only reason they went to the inline-three back in the day was because OMC was selling one, and it was a popular seller. So Mercury decided to match that with their own inline-three. Same thing with the Tower of Power sixes. OMC had the V-6 so Mercury built the inlines and V-6's side by side for a few years before finally discontinuing the inlines. But those Tower of Power inline-sixes were never surpassed by modern technology either. 20 years after they were built there was still thousands of 'em on ski boats used by ski teams because they had incredible torque and would pull a dozen skiers out of the water and not even breathe hard.

The newer stuff got newer, but not necessarily better.

 

[Faztbullet]

A 1971 would have a distributer....the picture shows coils and switchbox clearly a ADI ignition...which will not adapt to a 650 block or crank as crankshaft is different and longer and block end cap wont accept a ADI stator. A pic of the carbs will tell the story...