Is this old merc a 2.0 or 2.4?

[Vcaldwell0006]

This engine is sitting resting on a 1979 Allison SST that I’m currently in the process of restoring. The engine runs flawlessly and appears to have high compression heads 146-150psi on all six. Any help in determing the model year or if it’s a 2.0 or 2.4 150 or early 200 would greatly be appreciated. Serial number 5045421

 

[Faztbullet]

Most likely a 2L 175 from serial number….post picture or casting number of block and heads.

 

[Vcaldwell0006]

[No message]

 

[Vcaldwell0006]

[No message]

 

[flyingscott]

That comes up as a 1978 2 litre TOP motor. That motor was never a 175 or 200 hp those were V6s only. The inline six topped out at 150 hp. My info could be wrong there are people who are much familiar with those motors.

 

[Dukedog]

mixture of parts... serial number means squat with that one.. first gen. block half but has later model 5 petal horizontal front.. so no telling what ya got???

 

[Vcaldwell0006]

The block has for sure been lifted off of the mid a time or two, I’m just trying to figure out exactly what I have. There is no bore size stamped on these old two piece heads. I do see a couple 2s stamped on this block does that mean it’s a 2.4 200? Thanks

 

[jimmbo]

I found that Serial # is for 1978 175hp
It would be a 2 litre(122 cubic inches)

http://www.autorepairmanuals.biz/page/609766

 

[Dukedog]

The block has for sure been lifted off of the mid a time or two, I’m just trying to figure out exactly what I have. There is no bore size stamped on these old two piece heads. I do see a couple 2s stamped on this block does that mean it’s a 2.4 200? Thanks

those numbers are jus a manufacturing production type thing.. that serial number is on "clamp" so has no bearing 'bout what motor it is.. first gen. blocks were really lacking on any I.D. marks except for tha '80/'81 225.. only way ta know for sure is pull a head.. downside of that is those head gaskets are expensive plus tha bolt layout (bosses' siamesed against tha bores) is not tha best merc design.. "off n on" multiple times ..

if motor performs like it should i'd leave it alone being a first generation block "frankenmerc" until there's good reason ta open it up jus 'cause!.. its gonna run very good on that boat whatever it is!....

ya might get on S&F and post some pictures with information 'bout it (boat and motor).. several "Allison guys" there that like trackin' down stuff like that. I've gotten to old and lazy... ​

 

[Vcaldwell0006]

Appreciate the help maybe the S&F guys can help if I can get approved to join. This thing stumped me, I had to get on here and ask instead of reading other post like I’ve done for years haha. I’ll run her till I can get the 2.5 200 efi rebuild I’ll throw some goodies on it when the time comes.

 

[Dukedog]

yeah, hard ta tell.. if I was guessin being ona Allison, especially an older one that's still in one piece, someone probably knew what they were doin' with it.. worst case it would be a finger ported (first generation) block half with tha later horizontal front with later model carbs n good reeds with some added compression.. so it should run pretty good.. has tha gearcase had a lwp added? (some keep those when rig is sold).. if not, its gonna need it...

 

[Vcaldwell0006]

Yes it has a bobs kit on the lower I just removed it the other day, it has a crack on the cavitation plate. I’m gonna to have it welded back and hopefully get a little more life out of it. I’m currently stripping the boat to restore. I’m the third owner guy I bought it from was using it to crappie fish haha its been garage kept its entire life the floor is completely solid, the whole rear of the boat is aluminum and it looks to have been that way for 30 years. Also has a functioning homemade jack plate and Holley fuel pump. Someone definitely knew what they were doing with this thing back in the day. As I believe the original owner was from Frankfort Kentucky and had some sort of affiliation with mercury racing in the 80s. Hopefully in the spring I can post some pics of it once completed.