Newer 3.0L in place of an Older 3.0 QUESTIONS

[Rensch1983]

I have a project boat that is a 79 and has the 2 piece seal 3.0l 140hp engine. The engine has some cylinder wear and thought I would be able to get away with a set of pistons but noticed its bore is 4.040 and it looks like the service limit is 4.050 and I wont be able to bore it to 4.060 i guess

So finding a 3.0 older 2 piece seal engine is hard but ive found a fair number of the early 90s-up version. I know there are some differences but here is my plan:

Use my existing coupler (is it possible to fit the newer flywheel?)
Use my existing bellhousing (this will allow the engine to bolt in place to my boat)
Id use my manifolds/accessories and ignition along with the harness thats from my boat on the bellhousing now.


I know there are some differences in the heads I already have an adapter to that.

I guess my biggest unknown is the flywheel/coupler/bellhousing and will it work. I have a mc1 outdrive

 

[Scott Danforth]

I believe the 1991 and later 3.0 came with the 168 tooth flywheel (14") vs the prior 153 tooth flywheel (12-3/4")

i believe you must use the newer coupler and flywheel cover or source a smaller diameter flywheel

here are two choices

3.0L Flywheel (1990 & Later Engines, 12¾" diameter)

This is a factory GM 12-3/4 inch flywheel used on early model 3.0L engines in conjunction with the 2 piece rear main seal crankshaft.

www.michiganmotorz.com

Flywheels & Couplers — We're More Than Just Engines

www.eagleenginesales.com

I am pretty sure that the 3.0 uses the same flywheel as the 5.7, however would have to verify.

you can also simply order a new engine already set up for old application. https://www.perfprotech.com/30l-inl...8-1990-replacement-gm181base2m/product/243612

If it was me, I would be looking for as late a 3.0/alpha 1 gen 2 longtail that I could find and transfer everything pulley to prop

 

[Bondo]

Ayuh,... Welcome Aboard,..... The coupler, 'n flywheel will Not swap,.....

Sierra sells a retro-fit coupler for stuffin' a newer bolt pattern crankshaft/ motor into a MC-1 driveline,.....

 

[Rensch1983]

Ayuh,... Welcome Aboard,..... The coupler, 'n flywheel will Not swap,.....

Sierra sells a retro-fit coupler for stuffin' a newer bolt pattern crankshaft/ motor into a MC-1 driveline,.....

so id be able to use my bellhousing and I just have to buy the coupler? I was under the impression that you needed to run a smaller flywheel to fit into the older boat bellhousing?

 

[Rensch1983]

I believe the 1991 and later 3.0 came with the 168 tooth flywheel (14") vs the prior 153 tooth flywheel (12-3/4")

i believe you must use the newer coupler and flywheel cover or source a smaller diameter flywheel

here are two choices

3.0L Flywheel (1990 & Later Engines, 12¾" diameter)

This is a factory GM 12-3/4 inch flywheel used on early model 3.0L engines in conjunction with the 2 piece rear main seal crankshaft.

www.michiganmotorz.com

Flywheels & Couplers — We're More Than Just Engines

www.eagleenginesales.com

I am pretty sure that the 3.0 uses the same flywheel as the 5.7, however would have to verify.

you can also simply order a new engine already set up for old application. https://www.perfprotech.com/30l-inl...8-1990-replacement-gm181base2m/product/243612

If it was me, I would be looking for as late a 3.0/alpha 1 gen 2 longtail that I could find and transfer everything pulley to prop

that would be great but this boat aint worth that at at all.. so pretty much im stuck buying a flywheel and coupler to fit this engine into my older bellhousing so it will bolt in place and the coupler will work with my current mc1 driveshaft

 

[kenny nunez]

His inner transom engine mount spread is wider than an Alpha which is 9& 5/8”. Is there a 12& 3/4” flywheel with the small bolt pattern?
I wonder if the larger flywheel could be turned down to the 12&3/4” dimension so that the ring gear can be swapped over? Then everything will bolt in using the Sierra coupler. If there is no starter mounting hole for the straight pattern it is no big deal to drill and tap the hole. I have done that before on a V8.

 

[Rensch1983]

well i see on michigan motorz that they sell the 12-3/4 flywheel for this purpose like the link above shows and then the coupler id have to decide which one... just didnt want to spend 450 on a flywheel and probably 200 on coupler.. not sure if there were other options to save the money. its a old cheap boat just trying to do it on a somewhat budget.

 

[Scott Danforth]

a set of sleeves for the bores is $100

 

[Rensch1983]

a set of sleeves for the bores is $100

where are you sourcing a set of sleeves?

 

[Scott06]

where are you sourcing a set of sleeves?

Cylinder Sleeves - Free Shipping on Orders Over $109 at Summit Racing

Find Cylinder Sleeves and get Free Shipping on Orders Over $109 at Summit Racing!

www.summitracing.com

well i see on michigan motorz that they sell the 12-3/4 flywheel for this purpose like the link above shows and then the coupler id have to decide which one... just didnt want to spend 450 on a flywheel and probably 200 on coupler.. not sure if there were other options to save the money. its a old cheap boat just trying to do it on a somewhat budget.

Yes this 12&3/4" flywheel plus the coupler will adapt it to the old style flywheel cover. The MC1 uses a different rear motor mount spacing until I think 1981.

Might be worth taking the engine to a machine shop and have it measured before making a decision. I would think you could bore it again (assumed it was rebuilt previously to .040" over?) to .060" over and be ok with out sleeves

 

[Scott Danforth]

where are you sourcing a set of sleeves?

my local machine shop has Mahle sleeves in stock. however if you want to buy them yourself. Summit has them.

MAHLE Original 226-8247

Free Shipping - MAHLE Original 226-8247 with qualifying orders of $109. Shop Cylinder Sleeves at Summit Racing.

www.summitracing.com

you need to bore the block, heat the block and freeze the sleeve, then install.