Confused New Owner of an Old Boat

[Ptr.Torch]

I recently made a non-cash deal for an older boat.
What I think I have is an IMP "Thunder" from 1969.
Sporting an in-line, 165 HP 6 cyl (GMC?) engine
and a Mercruiser Stern Drive.

My book tells me I should be looking at a 250 GMC engine Moldel #160
The Stern Drive tells me its for a 120-140 Hp, Serial #2824078, which has a cracked lower housing.

Did someone replace the Lower unit with one that is undersized, or maybe replaced the 4 cyl with the 6 cyl? And is this mis-match likely the cause for the lower unit being split open?

More to the point, what is going to be the easiest and best way to fix this??

Any info would be appreciated. Just assume I know almost nothing about boats.... (grin).

 

[alldodge]

Welcome

Sporting an in-line, 165 HP 6 cyl (GMC?) engine
and a Mercruiser Stern Drive.

My book tells me I should be looking at a 250 GMC engine Moldel #160

The motor is a 250 cu in inline 6 with 165HP, Merc uses its HP rating

The Stern Drive tells me its for a 120-140 Hp, Serial #2824078, which has a cracked lower housing.

The serial number on the drive can be used on many motors. This LINK shows the 165 with same serial number band

 

[Bondo]

I recently made a non-cash deal for an older boat.
What I think I have is an IMP "Thunder" from 1969.
Sporting an in-line, 165 HP 6 cyl (GMC?) engine
and a Mercruiser Stern Drive.

My book tells me I should be looking at a 250 GMC engine Moldel #160
The Stern Drive tells me its for a 120-140 Hp, Serial #2824078, which has a cracked lower housing.

Did someone replace the Lower unit with one that is undersized, or maybe replaced the 4 cyl with the 6 cyl? And is this mis-match likely the cause for the lower unit being split open?

More to the point, what is going to be the easiest and best way to fix this??

Any info would be appreciated. Just assume I know almost nothing about boats.... (grin).

Ayuh,...... Welcome Aboard,...... Donno whether yer motor or drive was swapped, coulda been either, or both,....
No doubt, you now have a mismatch,.....
The drive coulda worked with that motor, although the gear ratio would be wrong, causing over-reving, 'n lower that expected speeds,.....
That alone, is not the reason for the lower unit failure,..... If the case is split, odds are it had water rather than oil in it, 'n freezing water split the case,....

To move forward, do a compression test on the motor to see if it's worth saving, then get it running,....
If the motor is Ok, you'll need an outdrive with either the 1.65/1, or the 1.84/1 gear ratio, which should run just fine, with the window of prop pitches normally easily available,....
You can run either the MC-1, or the Alpha 1 outdrive, in the ratios noted above,.....
Be forewarned, the yer set-up requires the shorter input shaft on the drive, not the standard longer shaft on many MC-1s, 'n on All of the Alpha 1s,....
Only the GM in-line motors on only the MC-1s uses the shorter in-put shafts,.....
If you end up buying an Alpha 1 drive, you can swap the shorter input shaft from yer MC-1 onto it, so it'll fit properly,....