Converting Mercruiser MC-1 to Alpha

[ToddCave]

Hello all,
I have been having some major issues with my MC-1 and I got some good advice here. I think that the best "middle ground" solution for me that is not insanely expensive but also not just putting a band-aid on things is to upgrade my drive to something newer than an MC-1. My engine is an old (late 60s) GM inline 6, 160hp. I think I'm going to put an alpha on there, but I just have a few questions before I commit to this too much more.
1) My understanding is that I can really only put an alpha 1, gen 1 on without major headaches... is that correct, or could I go up to a Gen 2?
2) just so I'm clear on the process, it's really just a matter of: (a) Disconnecting cables/etc from the motor and pulling the motor; (b) taking off the inner transom plate and gimbal/bell housing and outdrive (drive is already off); (c) buying an alpha gimbal/bell housing and outdrive; (d) installing the new gimbal and bell housings while the motor is out, which might require drilling new holes and cutting away part of the transom; (e) putting the motor back and reconnecting everything; (f) putting the new outdrive back on. Is that generally that process? Will I need specialized tools or anything? I have a bearing alignment tool, anything else?
3) I also understand that there may be some differences in shaft length and gear ratio that make this not quite a bolt-on project. How can I check those things?
4) Any tips on buying used alpha outsdrive/housings? Things to look for, good sources to buy from, etc.? If I get the inner transom plate, gimbal housing, bell housing, and outdrive, I'm pretty set, right?

Anything else I should know before taking this on? I have the repair manual for my outdrive/motor combo, I have the bearing alignment tool and puller tool, I have access to a hoist... anything else I should have before attempting this?

Thanks!! Looking forward to diving into this project.

 

[matt167]

Does your drive use a cable for tilt or does it have trim rams? If it has the cable, then it's the older style.. If it has trim rams, then you can likely keep your transom plate, change the gimbal bearing and bellows, and then put an SEI drive on it... If you have to mess with the transom plate, you might as well dump the old I6 in favor of a 4.3L. Get a 4.3L and Alpha 1 Gen II from a donor boat that's rough but runs good

 

[ttownthomas]

I also have inline 6's. I opted to buy rebuilt gimbal assemblies on Ebay and you can then either get sei drives or a1g1 and swap over the yoke

 

[ToddCave]

Does your drive use a cable for tilt or does it have trim rams? If it has the cable, then it's the older style.. If it has trim rams, then you can likely keep your transom plate, change the gimbal bearing and bellows, and then put an SEI drive on it... If you have to mess with the transom plate, you might as well dump the old I6 in favor of a 4.3L. Get a 4.3L and Alpha 1 Gen II from a donor boat that's rough but runs good

Thanks. I think my gimbal housing is pretty much done for... it cracked trying to get the bearing out; bearing was corroded in there pretty good.

I worry a little about buying a new engine, because I know the one I have now is decent, but I just wouldn't trust myself to know how to inspect some engine off of a damaged boat. I feel like there's a good chance that I end up with a worse engine than I have now...

 

[matt167]

Thanks. I think my gimbal housing is pretty much done for... it cracked trying to get the bearing out; bearing was corroded in there pretty good.

I worry a little about buying a new engine, because I know the one I have now is decent, but I just wouldn't trust myself to know how to inspect some engine off of a damaged boat. I feel like there's a good chance that I end up with a worse engine than I have now...

The problem is cobbling up what you need to make the I6 work. It really wasn't used past 1977 I think. It may have gone a little later, but the infamous 470 actually replaced it, and then the 4.3L replaced that. So you can get to an Alpha 1 Gen 1, but it will take some older parts from a later model Inline 6 to make it work. Possibly even the manifolds. You should be able to use a little of this and a little of that to get it running.. But jumping to a 4.3L in an Alpha Gen II will be more reliable and likely cheaper as well as gaining 50-75hp

 

[ToddCave]

The problem is cobbling up what you need to make the I6 work. It really wasn't used past 1977 I think. It may have gone a little later, but the infamous 470 actually replaced it, and then the 4.3L replaced that. So you can get to an Alpha 1 Gen 1, but it will take some older parts from a later model Inline 6 to make it work. Possibly even the manifolds. You should be able to use a little of this and a little of that to get it running.. But jumping to a 4.3L in an Alpha Gen II will be more reliable and likely cheaper as well as gaining 50-75hp

hm. Okay, well, this wasn't on my radar before, but I'll consider it as an option (thanks for pointing this out as a possibility). I'm still a little nervous about buying a salvage/damaged boat... anyone have any advice? What's the process? Do I just, like... buy some piece of garbage off craigslist and hope it runs? I should be looking for "damaged" boats rather than "TLC-needed, it ran last year" boats, right? What do I do with the donor boat? Is this a 1-3 day project if I'm able to put in like 8-10 hours a day? I live in an an apartment and my main boat is in dry storage (i rent one spot), so it's not like i have a 3-car driveway or garage or anything to do this work. I might be able to park the donor on the street for a few days but not weeks. And then what, I just... sell the donor hull? Or do most people put the old engine in the donor hull and sell that whole package, or, like, part out the old engine? Never done this before, looking for any guidance on the process so I can get a sense of whether this is the right move. Thanks!

 

[matt167]

If you buy a donor boat, you can have the engine out with a chainsaw in 10-15 mins. Since the Alpha Gen II came out in 1992 IIRC, there are lots of rotted Brunswick boats ( Bayliner and many others ) that can be had...

Being you have a late 60's boat though, asses your boats structural integrity as well

 

[achris]

You have the early MC1. To go to either of the Alpha drives you'll need to change the inner transom plate, and that means the existing flywheel housing on the engine will no longer work. The newer (1982 and later) flywheel housing from a 3 litre engine should bolt straight on. I would also take the new style engine coupler, which means (very accurately) drilling and tapping the 160's flywheel. That will enable you to use the longer (standard) input yoke.

You will also need to do some modifications around the exhaust...

Chris....

 

[Lou C]

Sounds like a lot of work/figuring to make it work. But I guess parts are just not available to rebuild those old drives. A complete change to the 4.3/Alpha Gen 2 would seem to be the best in terms of finding parts and keeping it going. It is a shame to give up on the old inline 6 but to keep the boat reliable moving to a newer drivetrain makes any future repairs easier. I have a stash of good used Cobra parts that I collected over the past year just for that reason. Though of converting it to a Volvo SX but Cobra parts are far cheaper and just as available used…

 

[ToddCave]

I have a very dumb question about this conversion. After thinking about what @matt167 mentioned about just switching to a gen II, I'm seriously considering it. I'm calling a few salvage yards and I'm realizing that I'm just not sure what I need to be buying. Will literally any 4.3L mercruiser motor work? Do I need to be asking for anything specific? Do I need any extra parts beyond the motor, the gimbal/bellhousing, and the outdrive?

Just trying to make sure I can get everything I need all at once, and I'm not scrambling for a part halfway through (or worse, realizing that I bought the wrong engine!)

Thanks!!

 

[Lou C]

Due to changes over the years you want there to be compatibility between the year of the drivetrain and engine. So if you are doing alpha 1 gen 2 then you want a 96 and up Vortec engine

 

[ToddCave]

Due to changes over the years you want there to be compatibility between the year of the drivetrain and engine. So if you are doing alpha 1 gen 2 then you want a 96 and up Vortec engine

Ah okay thanks. So basically any 1996+ 4.3L (vortec) will work? And will that mount right onto my old mount (GM inline 6)? Any other parts I need, or is it basically just pulling the old motor and dropping the new one in and hooking up gas/electrical? I mean, I know it's more complicated than that, I.m mostly asking about things like when you switch from a MC1 to a alpha gen1, you need to like change the flywheel cover and drill special holes and stuff. Just wondering if there's anything like that for a switch to a alpha1, gen2 with a 4.3L.
Thanks!!

 

[nola mike]

Ah okay thanks. So basically any 1996+ 4.3L (vortec) will work? And will that mount right onto my old mount (GM inline 6)?

No, the mounts are different. You'll likely need to fabricate/glass in front mounts

Any other parts I need, or is it basically just pulling the old motor and dropping the new one in and hooking up gas/electrical?

Depends on what you're buying. You'll need *everything* off the new motor, water pump, intake, ignition, flywheel, coupler, carb, fuel pump, etc. Maybe controls and wiring harness. Better off buying a junk boat and having what you need for sure.

I mean, I know it's more complicated than that, I.m mostly asking about things like when you switch from a MC1 to a alpha gen1, you need to like change the flywheel cover and drill special holes and stuff. Just wondering if there's anything like that for a switch to a alpha1, gen2 with a 4.3L.
Thanks!!

 

[Lou C]

Agreed you are better off buying a rotted boat for the whole drivetrain and all the assorted bits that will nickel dime you on these conversions

 

[ToddCave]

No, the mounts are different. You'll likely need to fabricate/glass in front mounts


Depends on what you're buying. You'll need *everything* off the new motor, water pump, intake, ignition, flywheel, coupler, carb, fuel pump, etc. Maybe controls and wiring harness. Better off buying a junk boat and having what you need for sure.

Ah ok, thank you. I should have mentioned, this is an old starcraft aluminum, which I guess should make mounting easier.

But good point on the extra stuff... water pump, intake, etc. My worry with getting a donor boat is that I don't know how to assess whether or not a used motor is in good condition... I'd hate to buy something that leads to more problems down the road. I'm also not seeing a lot of damaged boats online, is there a better place to look than craigslist? I'm checking the whole western half of the US and not seeing much, maybe I just need to keep looking. Or are there any good salvage yards or something that tend to have parts that people here like and trust?

Thanks!!

 

[matt167]

There are various boat junkyards across the USA that will have just what you want. There are also boat storage yards that have unpaid storage/ abandoned boats for years and they will sell those boats usually

 

[nola mike]

Ah ok, thank you. I should have mentioned, this is an old starcraft aluminum, which I guess should make mounting easier.

But good point on the extra stuff... water pump, intake, etc. My worry with getting a donor boat is that I don't know how to assess whether or not a used motor is in good condition... I'd hate to buy something that leads to more problems down the road. I'm also not seeing a lot of damaged boats online, is there a better place to look than craigslist? I'm checking the whole western half of the US and not seeing much, maybe I just need to keep looking. Or are there any good salvage yards or something that tend to have parts that people here like and trust?

Thanks!!

There's plenty on Craigslist, look for $1k junk boats. Even get something with a cracked block. I'd assume that any motor from a trashed boat is also junk and needs a rebuild. Mine had cracked block and manifolds unknown to me when I bought it. Got a truck block from the pull a part for $180. Imo, any used truck block that you get will be better and cheaper than a used marine version