Mercruiser inline six upgrade compatibility?

Mercruiser inline six upgrade compatibility?

Greetings all,
Newbie here hoping to learn and share some down the current.

I have an original Mercruiser 150 in a 1966 21'. I'd like more power and something a little fresher. The gm 230 grew to be to the 250CI Mercruiser 165.

The basic block was also used for the 292. Short lived in the Mercruiser 200 of 1969. I'm hoping to learn if the 292 is a feasible swap and what needs to be done to swap the MC 1-C ez shift to an Alpha or Bravo drive. The original drive mated to the 292 was the MC II - not an option.

I don't want to expand the sole or the engine cover to put ina small block, so getting the most torque and HP I can get reliably with out going hi-performance is my target from the bigger inline 6.

I currently have the old 2 carb manifold and would like to run with one so Im guessing Ill be looking for a 165 motor to at the very least swap some external parts. I do expect I'll swap the points for Pertronix kit but other than that Im thinking stay old school.

I appreciate any and all thoughts as I'm pretty naive on the subject.​

The 292 is the same external size as the 230 and 250. The fuel pump is located in a different position of the 292 block which makes them easy to ID. If you are going to use a 292 from truck or bus, the camshaft from the marine engine must be used. This will put the cam lobe in the wrong place for you to use a mechanical fuel pump. Just get a block off plate and use an electric pump.

The basic block was also used for the 292. Short lived in the Mercruiser 200 of 1969. I'm hoping to learn if the 292 is a feasible swap and what needs to be done to swap the MC 1-C ez shift to an Alpha or Bravo drive. The original drive mated to the 292 was the MC II - not an option.
I don't want to expand the sole or the engine cover to put ina small block,

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Ayuh,... Welcome Aboard,.... I donno what the keyhole looks like for the MC-II, so I can't tell ya how to go to the MC-1, or Alpha, or the Alpha, Gen.II, 'n Bravo keyhole,.....

I know there's 2 bolt holes that moved durin' the MC-1s, after yer boat was built, 'round the early '70s,....
After that, the keyhole carried through out the Alpha 1s,....
The Bravo came out in the late '80s, the keyhole stayed the same, but 2 more bolts were added, then in '91 with the Alpha, Gen.II, it also used the extra 2 bolt holes, makin' the keyhole standard for drives since then,....

If yer gonna refit/ re-power the barge, shoot for the moon,...
Find a solid runnin' motor/ drive in a rotten or crashed hull, 'n Go for it,...

How much modifyin' does the motorbox need to drop in a V-motor,..??

If you are going to use a 292 from truck or bus, the camshaft from the marine engine must be used.

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Oh,..... I strongly disagree with this quote,....

Truck cam, bus cam, marine cam, virtually No differences at All,....

Greetings Guys,

Thanks for the welcome, and for the input.
I'm actually looking at a remanufactured 292 and hoping to use externals from my 150 or a decent 165. Also looking for a good 165 in case the 292 idea doesn't pan out...

Can the 165 be mated to an Alpha I or Gen II drive?

I believe the cam is included and expect the cam will be be fine.

The fuel pump difference is understood. I'll have to look at the manual while sitting in the boat to see if that change to electric is necessary.

As far as the motor box mod, its really a matter of glass work. A friend with the same boat, changed his floor and expanded the box about 16 inches to stick a SBC 383 stroker in there. The big difference is my boat is 50 y.o., virtually original, and only about half dozen known to exist. His was pretty shot. But he's a master craftsman which I am not, and I'm not sure I can manage the rigors of the required glass work. I think I can work with the extra 1-3/4" deck height of the 292.

Regarding the keyhole, again mine is the MC 1-C. My understanding is it has a different transom assembly, incompatible with the Alpha drive. Is that change as simple as changing the transom assembly. I'm pretty sure I'll have to change the transom assembly either way as I'm pretty sure the greater torque of the 292 would destroy the old MC 1-C.

There may also a question of exhaust but that might only apply to using the obsolete MC Mod. II stern drive.

Attached is a picture of my SeaSaw cuz everybody loves boat porn

Right. Both cams are ground for low end and mid-range torque.

Jeff

It needs the casting for the motor mount but one can be fabricated to accept the front mount using 3/4 alum angle.
Will need wet exaust hose to connect riser to pipe. 292 is a bit taller.
But with a .030 bore and a slightly hotter cam it is a powerhouse.

Sorry been out of the loop. Appreciate your replies.

Hang ups w/small block would require cutting up a perfectly good sole and expanding the hole and box about 8" per side. Original spatial layout would be altered and I prefer the cockpit sole space as is corner space is key for fishing grumpy tuna and yellowtail.

Weight would move aft dramatically and a CG would move up and aft. Don't want that.

Current 230 uses 50 year old 1.65 ratio MC-1c ez shift. Although recently redone, guessing a 292 or even a 250 would destroy it. And parts are ridiculously expensive through repair shops as many parts pop as NLA.

Pretty sure the transom assembly, steering, etc., is all different for the Alphas as Bondo suggested. Thinking Alpha one Gen 2. If I swap out the transom/gimbal assemblies for Alpha Gen 2, either motor should be compatible, right?

Do I stick with a 1.62 ratio or would I have to have to move to 1.5. Or could I swing more prop with a 1.84.

Thanks again,

Seafari

Pretty sure the transom assembly, steering, etc., is all different for the Alphas as Bondo suggested. Thinking Alpha one Gen 2. If I swap out the transom/gimbal assemblies for Alpha Gen 2, either motor should be compatible, right?

Do I stick with a 1.62 ratio or would I have to have to move to 1.5. Or could I swing more prop with a 1.84.

Click to expand...

Ayuh,.... The Gen.II oughta work Ok,... A Chevy bell, is a Chevy bell,....

The coupler might turn into an experiment though,...
The outdrives input shaft was shorter on the in-line Chevys with the MC-1s,...
It'll be a mix/ match of flywheels, couplers, 'n flywheel covers to see how it fits up,...

What pitch props ya spinnin' now,..??
The window of easily available prop pitch is 15" to 23",...
Ya might wanta try the 1.84,... a 1.50 will be too tall,...