Help and clarification

[Jokitsu90]

Hi all!
I have had for a couple years now, an older 1973-75 StarCraft (most of the decals, serial numbers, etc. Have been weathered away I also believe that the upper and lower were fitted onto a different year motor) it has a mercruiser 165hp 3.7l straight 6. I was told when I bought it it was an alpha one gen 1. I feel like maybe this isn't the case? Pre alpha maybe? Whenever I look for parts I have a hard time finding what I'm looking for and some parts I get are absolutely wrong, even though they state alpha one gen 1. I do find most the time they work but I know there is significant interchange in earlier models so am I getting lucky? With that being said I am looking for a part number for the lower oil seal that seats around the drive shaft, and everywhere I look I get different numbers. I am on a time limit for this one and I don't want to have to send back something that doesn't work. Does anyone have the part number they can share with me?

 

[dubs283]

You own one of the greatest engines produced in the past 70 + years of American capitalism. Cheers


Your setup requires a present, logical representative of said boat.

 

[kenny nunez]

If you are looking for the lower seal that is installed from the bottom of the upper gearcase this should be it. It is just over 1” in diameter. The inner hole is 7/8”
Mercruiser #. 25-96503
Sierra#. 18-2056

 

[nola mike]

The 470's first year was '76. So who knows what you have in there. Post some pics
Edit: rereading... Do you have a 4 or 6 cyl? Don't think there was a 3.7l 6.

 

[Jokitsu90]

If you are looking for the lower seal that is installed from the bottom of the upper gearcase this should be it. It is just over 1” in diameter. The inner hole is 7/8”
Mercruiser #. 25-96503
Sierra#. 18-2056

That's exactly what I'm looking for! Thank you so much. I'm not a professional by any means so I'm really trying to learn as I go! I love this boat and have put a lot of work into it but since I'm unsure of exactly what it is and it having many previous owners everything is kinda hodgepodge I also noticed some scoring on the lower unit drive shaft. Looks to be about where that seal sits. Is this something I should look into replacing?

 

[Jokitsu90]

I have the lower off currently since I needed to replace the seal but there she is. And yes I paid to have a hitch put on my caddy

 

[Jokitsu90]

The 470's first year was '76. So who knows what you have in there. Post some pics
Edit: rereading... Do you have a 4 or 6 cyl? Don't think there was a 3.7l 6.

I posted pictures

 

[achris]

Full identification (after viewing the photos)...

The engine is a 4.1L (250cu in) GM 6 cylinder. They were used as 'Mercruiser 165' between 1970 and 1981. Other things indicate it's prior to 1976 (no gimbal mounted trim sensors). The drive is most definitely NOT an Alpha One, it's a Mercruiser 1-drive (MC1), after 1974 (plastic water pick up inserts on the gear housing). So, I suspect you have an engine and drive of between 1974 and 1976...

Hope this helps.

Chris......