3.0L comparability

[1966starcraft18ft]

Hey guys, so I’m in search of some compatibility info. As you all know, my sons and I picked up a 1976 Silverline tri-hull boat that’s got a mercruiser 140 in it. I have since found that the block has sat with water in it and the exterior of the block up in behind the intake has cracked. My preliminary inspections with my borehole indicate that the crack is exterior only.

So now I’m weighing my options for a repower. My question is, can I take a newer 3.0L like a 3.0L LX and swap it in?

More curious if bell housing bolt pattern changes, crank bolt pattern changed, ex.

 

[Scott06]

the

Hey guys, so I’m in search of some compatibility info. As you all know, my sons and I picked up a 1976 Silverline tri-hull boat that’s got a mercruiser 140 in it. I have since found that the block has sat with water in it and the exterior of the block up in behind the intake has cracked. My preliminary inspections with my borehole indicate that the crack is exterior only.

So now I’m weighing my options for a repower. My question is, can I take a newer 3.0L like a 3.0L LX and swap it in?

More curious if bell housing bolt pattern changes, crank bolt pattern changed, ex.

the flywheel size and coupler mounting changed in 1990 when the 3.0 went to a one piece rear seal. so as long as you have a complete bobtail it will work with one hitch- the rear motor mount spacing changed when the R.MR, Alpha one was introduced in 1982 ish. So you would need the later flywheel cover swapped for your older one , assuming it fits over the larger flywheel diameter. I would think it would ... given the bolt pattern is the same.

other way I believe you can swap a newer inner transom plate off a alpha to your MC1.

Best bet if you can find a complete tear out with a alpha gen 1 or 2 engine , transom and outdrive and swap it in, then everything is current. If you want to keep the boat that would be the best route.

Have you verified the transom and stringers are ok before throwing more cash at it?

 

[1966starcraft18ft]

I haven’t inspected stringers yet but I do know transom wood is solid.

 

[nola mike]

the

the flywheel size and coupler mounting changed in 1990 when the 3.0 went to a one piece rear seal. so as long as you have a complete bobtail it will work with one hitch- the rear motor mount spacing changed when the R.MR, Alpha one was introduced in 1982 ish. So you would need the later flywheel cover swapped for your older one , assuming it fits over the larger flywheel diameter. I would think it would ... given the bolt pattern is the same.

other way I believe you can swap a newer inner transom plate off a alpha to your MC1.

Best bet if you can find a complete tear out with a alpha gen 1 or 2 engine , transom and outdrive and swap it in, then everything is current. If you want to keep the boat that would be the best route.

Have you verified the transom and stringers are ok before throwing more cash at it?

I can't remember offhand the details about input shaft length and older inline MC-1s, but that might come into play at some point...

 

[1966starcraft18ft]

I was hoping to be able to use my existing bell housing and coupler on the new motor so I didn’t have to redo the entire drive. That’s why I was asking about interchangeability

 

[Scott06]

I was hoping to be able to use my existing bell housing and coupler on the new motor so I didn’t have to redo the entire drive. That’s why I was asking about interchangeability

bellhousing likely will fit but coupler will not your old one bolts to crank ub via studs where flywheel attaches. Hub on newer engines (post 1990). So if you target getting a pre 1990 3.0 with 2 pc rear main seal the coupler will fit

 

[Scott06]

I can't remember offhand the details about input shaft length and older inline MC-1s, but that might come into play at some point...

yes that may be true as well, the early inlines (not sure the years) used a shorter input shaft. Unless you have all of it together in front of you or have done the swap expect some mixing and matching

 

[1966starcraft18ft]

Hey guys, so I’m in search of some compatibility info. As you all know, my sons and I picked up a 1976 Silverline tri-hull boat that’s got a mercruiser 140 in it. I have since found that the block has sat with water in it and the exterior of the block up in behind the intake has cracked. My preliminary inspections with my borehole indicate that the crack is exterior only.

So now I’m weighing my options for a repower. My question is, can I take a newer 3.0L like a 3.0L LX and swap it in?

More curious if bell housing bolt pattern changes, crank bolt pattern changed, ex.

Sorry. Bore scope, not borehole. Darn fat fingers

 

[Scott06]

Sorry. Bore scope, not borehole. Darn fat fingers

borescope won’t show if crack is through to the crankcase so you are right to find another engine

 

[matt167]

3.0 is commonly cracked externally and able to be patched…. However they are pretty cheap to buy good used.. going up to 1990, is an almost bolt in. need your rear mounts as the spacing is different, and the riser might need swapped.