TOPIC: 1968 Merc 1250 Exhaust Mystery

I have a problem that has stumped the folks on the motor forums.

I have a 1968 Merc 1250 125hp inline 6. While changing the water pump, I noticed it didn't have an exhaust tube. I saw it on the parts diagram but it's not in my motor. Members of another forum said I do have an exhaust tube and showed me the diagram for it. Seemed logical so I began my effort to restore the exhaust tube.

So, I purchased a used one and all the gaskets off ebay. When I pulled the exhaust extension plate, I noticed it did not look like the one in the diagram. It did not have an extension for the exhaust tube to slide over. So I went to the boat parts website to look it up and it shows two different part numbers for my motor. The one I have (48712) and the one that's pictured (52932). That leads me to believe that my motor came with and without an exhaust tube. Is this correct? The 52932 cross references to many motors, but mine (48712) is only for the 1250.

The new plastic water tube guide is all bubbled and melted from just one test day.

Everything is apart and I'm stumped as to what to do. Should I just put it back together? Or should I get the extension plate for the tube? Another factor is that there are also two different drive shaft housings for my motor, a 3669 and a 3918. I'm thinking that maybe that changes too?

I really need some help on this. The powerhead is currently hanging off the back of my truck on a borrowed hoist

Thanks,
Mark

and maybe 2 exhaust tubes

dave bernard wrote:

and maybe 2 exhaust tubes

They only show one exhaust tube for the 1250. It's part #38470. I have this and it does not fit.

Thanks,
Mark

So I think there are two versions, there is the tube all the way to the lower unit which isolates the exhaust and water then I believe there is a megaphone style which is a shorter rounder tube that does not extend down to the lower unit, the exhaust and water mix before exiting. I have never seen a megaphone style but parts list shows differing styles. The 1250 was a two year wonder and was the transition between the cross flow and the direct charge. It shares some features with earlier motors and has some features of the later in-lines. The distributor has a unique retard mechanism.
It would not surprise me that Merc had variations of the motor. I surmise it was touchy to make the HP and stay out of trouble detonation wise.
Randy

It turns out that the 68 did not have and exhaust tube, but the 69 did. I put it back together and will try to find out what parts will be required to make the update. So far it's the tube and extension plate for sure. Looks like maybe the interior swivel mount cover as well and no rubber grommets on them.

I put the tube in my housing and it's really tight and doesn't seem like they match. I'm basically trying to find out if my housing will work. If not, then it won't be practical to upgrade.