1966 Mercrusier Identification

[oldmanboat]

I just purchase a 1966 Shell Lake Boat with 120 HP Mercruiser I/O. I am trying to verify the model of my outboard (everything looks like it is orginal). There are no S/N or other identifying numbers on the outboad. From what I have read for this year it could be (Mecruiser I) or (Mecruiser Model IA/IB/IC EZ Shift). I did find on a plate on the inside of transom where the shift cable passes through with the words "Mecruiser I" printed on it. Can I assume that this is the model of my Outboard?

 

[Don S]

Re: 1966 Mercrusier Identification

120 HP Mercruiser I/O. I am trying to verify the model of my outboard

Welcome aboard.
Just so everyone talks the same language here, it's called an outdrive not an outboard.

One way of telling the difference in the 1B or 1 drives is to measure the 2 top mounting studs for the outdrive to the bellhousing.
From Center to center the 1B drives have a 4 15/16" dimention while the 1 drives have a 5-1/16" dimension.

You can also go up to the Adults Only sticky at the top of this forum and download an OEM service manual for your engine and drive. It has all the info for ID in it.

 

[JustJason]

Re: 1966 Mercrusier Identification

another way to narrow it down is by the trim/tilt system. Does it have the old old fashion cable tilt? Does it have hydraulic tilt only? (2 hydraulic lines) or does it have power trim (4 lines)

 

[oldmanboat]

Re: 1966 Mercrusier Identification

Thanks for the Weclome Don S. and for the quick tutorial on outboard vs outdrive.

I measured the top bolts, from center of bolt to center of bolt measures 4 15/16. So it seems that I have a 1B outdrive. According to my Manual it states that if I have a IB outdrive I "should not attempt to install a Mecruiser I drive even though the bold pattern is the same, the drive shaft will not align with the gimbal housing ball bearing".

I have a cracked a lowered unit that was JB Weld that I want to replace. I was going to replace the entire outdrive but finding a IB outdrive will be difficult. Are the lower units interchangeable on Mecruiser I vs. IB?

 

[Don S]

Re: 1966 Mercrusier Identification

According to my Manual it states that if I have a IB outdrive I "should not attempt to install a Mecruiser I drive even though the bold pattern is the same,

The bolt pattern is NOT the same, the Mercruiser 1 drive has a 5-1/16" distance between the top studs, You have 4-15/16 between centers.

 

[oldmanboat]

Re: 1966 Mercrusier Identification

That's what I was thinking also. The bolt pattern couldn't be the same if the bolt distance is different. Not sure why the Manual states this?

Do you know if the lower units are the same for Mercruiser I vs IB?

 

[Don S]

Re: 1966 Mercrusier Identification

Not sure why the Manual states this?

What manual have you got?

 

[oldmanboat]

Re: 1966 Mercrusier Identification

It the original Mercruiser Service Manual. Vol 1 and 2 #C-90-68648.

 

[oldmanboat]

Re: 1966 Mercrusier Identification

another way to narrow it down is by the trim/tilt system. Does it have the old old fashion cable tilt? Does it have hydraulic tilt only? (2 hydraulic lines) or does it have power trim (4 lines)

JustJason your asked the following:

(Does it have hydraulic tilt only? (2 hydraulic lines) or does it have power trim (4 lines)

My outdrive has the hydraulic tilt (2 hydraulic line). Does this confirm that I have a 1B EZ shift.

 

[JustJason]

Re: 1966 Mercrusier Identification

if you have 2 lines only then you have either an A B or C.... but that doesn't help you. It's closer to the 90 drive than anything else. You have an oddball my friend. Back in those days if you had a 120HP engine then the drive was a 120 drive... etc. We're going on 40 years old here.
I'm fairly certain that A B and C were interchangable to a degree. But after the ABC it went to HP numbers. I don't believe the ABC's and the HP # drives are interchangeable.