Mercruiser MC-1 versus Alpha-One - input capacity

[region4]

I am dealing with older V8 mercruisers (260 and 233 and 188) in 1970-era boats; It seems that one can rebuild yesteryears V8's, and get more torque and horsepower (RPM), than originally spec'd when new.

In general, I would most appreciate advise on how the drives handle abundant power.

1. How much input horsepower can the MC-1 handle, versus the Alpha-One?

2. Does the gear ratio affect input capacity? In other words...does the 1.32 ratio have intrinsicly less capacity than, say a 1.50 and up, because it drives the prop shaft a higher speeds, relatively?

3. What are 'heavy duty' gears sets? What drives got them, and how are they beefier?

4. Can well maintained fresh water drives last a lifetime (as in human)? It seems that there exist many older boats with little hours and which are in good condition.

 

[Scott Danforth]

Re: Mercruiser MC-1 versus Alpha-One - input capacity

yes you can build a SBC to have a huge amount of power. you can build up to about 440 cubic inches and about 600hp naturally aspirated. more hp if you add a super charger.

1 - about 300hp per the factory. however many people on scream and fly are putting between 400 and 500hp to the A1G2 drives with stroker motors. they have to watch the hole shot, as well as chop the throttle if they catch air.
2 - to some extent. the gear ratio gets the RPM's in line to match available props
3 - the SS drives had the heavy duty gears. However you can build your drive to match or exceed RLC performance makes (or used to make) custom Alpha drives. RLC Performance Engineering depends on what you want to pay.
4 - anything man made will fail. it is all dependent on the maintenance and care. many drives from the 60's and 70's still going strong.

 

[Bondo]

Re: Mercruiser MC-1 versus Alpha-One - input capacity

I am dealing with older V8 mercruisers (260 and 233 and 188) in 1970-era boats; It seems that one can rebuild yesteryears V8's, and get more torque and horsepower (RPM), than originally spec'd when new.

In general, I would most appreciate advise on how the drives handle abundant power.

1. How much input horsepower can the MC-1 handle, versus the Alpha-One?

2. Does the gear ratio affect input capacity? In other words...does the 1.32 ratio have intrinsicly less capacity than, say a 1.50 and up, because it drives the prop shaft a higher speeds, relatively?

3. What are 'heavy duty' gears sets? What drives got them, and how are they beefier?

4. Can well maintained fresh water drives last a lifetime (as in human)? It seems that there exist many older boats with little hours and which are in good condition.

Ayuh,.... They're virtually the Same drive,.... Both will take 300 hp,... for awhile anyways,...

 

[haulnazz15]

Re: Mercruiser MC-1 versus Alpha-One - input capacity

Agreed, scott.

MC1 and Alpha One both handle 300HP.

Technically, the lower gear ratio is more "robust" simply due to physics, but it's not made any stronger. The 1.32ratio from the 233's (and some big blocks) is pretty rare anymore, and I think the gear sets may be NLA.

As above, the SS Alphas got the HD gear sets.

Also as above, drive lives are dependent on maintenance and care when in operation. The lower units are generally more likely to have failures due to the FWD/REV dog clutches and such, where the uppers are pretty much bulletproof as long as they are kept cool and lubricated.

Side note: you can't upgrade a boat engine like you can a car engine. The drives are RPM-limited, usually to less than 4,500 or so. Hot Rod car engines use cams that have the powerband all the way into the upper 5K rpms but you can't build a boat engine that way. Also, you will run into what is referred to as "reversion" in the exhaust when your cam has too much lope in the idle, which can cause water to be ingested into the combustion chamber from the exhaust port. You will need to look into different exhaust options at that point.

 

[Scott Danforth]

Re: Mercruiser MC-1 versus Alpha-One - input capacity

Agreed. Thru-hull exhaust needed on most cams above 270 degree, especially at idle. also, the lobe separation needs to be watched. beyond a point, dry-exhaust is required

Synthetic oil helps bring the RPM limit of the drive up. I thought most Mercruiser drives had a 5500 RPM limit.

I think the OP's intention is to find the limits of the drives within the reasonable guise of a mild rebuild.

Then again, if we are building a high HP motor, I would want to put the motor in front of a proper Mercury Racing XR, NXT or an ASD drive depending on the boat.