1974 Mercruiser 140hp transom assembly replacement options

[Chevyls6]

Does anyone know what transom assembly, if any, will be a direct swap for a 1974 140hp? The one that's on there now is an early style with the trim limit switch at the top and non threaded pins for the bellhousing. I can find a direct replacement for the gimbal housing on ebay but the gimbal ring itself is nla everywhere ive looked.

Ideally I would like to reuse the inner plate so i won't have to mess with repositioning the front engine mount.

 

[Chevyls6]

I believe i have an MC-1 drive based on my serial number.

 

[Scott Danforth]

Ideally I would like to reuse the inner plate so i won't have to mess with repositioning the front engine mount.

any time you touch any of the screws on any mount, you need to re-align the motor. you should be checking alignment every year as part of your annual maintenance.

no way to get around alignment if you pull the motor to remove the transom plate.

I suggest finding a complete 1992 or later 3.0 and Alpha 1 Gen 2 drive

 

[Scott06]

Does anyone know what transom assembly, if any, will be a direct swap for a 1974 140hp? The one that's on there now is an early style with the trim limit switch at the top and non threaded pins for the bellhousing. I can find a direct replacement for the gimbal housing on ebay but the gimbal ring itself is nla everywhere ive looked.

Ideally I would like to reuse the inner plate so i won't have to mess with repositioning the front engine mount.

The MC1 transom plate has different rear engine mount spacing than post 1981 alpha transom housings.
@Bondo would probably know what you can mix and match

i assume you intend to keep your engine and drive? if the boat is in good shape and you want to keep it for a while (. Aka worth investing) best long term option is to get a rotten boat with a 92 and newer 3.0, swap the entire driveline, then nothing will be obsolete.

 

[nola mike]

The MC1 transom plate has different rear engine mount spacing than post 1981 alpha transom housings.
@Bondo would probably know what you can mix and match

i assume you intend to keep your engine and drive? if the boat is in good shape and you want to keep it for a while (. Aka worth investing) best long term option is to get a rotten boat with a 92 and newer 3.0, swap the entire driveline, then nothing will be obsolete.

The flywheel housing is different as well iirc, as is the flywheel and coupler from newer models (though not sure if that would have an impact)

 

[Scott06]

The flywheel housing is different as well iirc, as is the flywheel and coupler from newer models (though not sure if that would have an impact)

Correct the flywheel housing has the different spacing as well.

 

[Chevyls6]

To clarify the situation a bit, I already have the engine out and rebuilt on a stand. I want to use the original engine and the new exhaust parts that i already paid for. I see that i can still get parts for the mc-1 drives with gimbal trim sensors. Can i just swap the whole gimbal assembly from a newer mc-1 with the updated gimbal design?

 

[Chevyls6]

Would something like this be a direct swap?

Z1 Mercruiser Pre Alpha transom assy assembly gimbal ring housing parts. | eBay

<p dir="ltr" style="margin-top:0; margin-bottom:0;">Z1 Mercruiser Pre Alpha transom assy assembly gimbal ring housing parts. Preowned. </p>

www.ebay.com

 

[kenny nunez]

The bolt pattern was moved to compensate when the housing was widened for the trim & limit switch senders. So your current inner transom plate will not fit.

 

[Chevyls6]

That is unfortunate. Does anyone know if i can modify a V engine gimbal housing for use with inline units? I have a tig welder so welding it is no big deal.

 

[kenny nunez]

The centering nose on the V8 gimbal housings that lines up and centers the inner plate is larger, while it may be possible to open the hole on your inner plate the exhaust flange on the V8 is different from the in line housing.

 

[Chevyls6]

From your experience does the one in that ebay ad look like a 4 cylinder model? I compared part numbers for inline vs v8 online and it appears the v8 has 3 ribs on each side of the gimbal bearing boss while the 4/6 cylinder has only 2.

 

[kenny nunez]

Also the in line exhaust only has 3 bolt holes for the exhaust pipe and the V8 could have 4 or 5 mounting holes.
It appears to have been sold and I could not get a look at it, did you buy it?

 

[Chevyls6]

Yes i made an offer and they took it. The gimbal housing on my boat right now has the same 3 passage 5 bolt pattern as this one but only the top 3 are used for the oval shaped exhaust pipe. It's no issue to plug the extra holes if needed. I also got the matching inner plate from ebay for a good price.

 

[kenny nunez]

Go ahead and replace the trim & tilt limit switches, be careful removing the 2 bolts that secure the wire harness as the break easy and tend to be corroded.
Best to remove the bell housing and bellows to get to the bolts with some heat.
You will have to expand the transom cut out and drill 2 new holes.
You will probably need another shift cable kit.
Sierra # 18-7633
MM #. 805320A03
Trim-Tilt limit kit.

 

[Chevyls6]

Doesn't sound too awful to make it work. I have all the new bellows that were intended for my other drive. Thankfully the part numbers appear to be the same. May as well delete my old hydraulic trim sender too while im at it.

At this point im contemplating throwing a new transom together since its so easy to get the old one out being an aluminum hull.