What rotation do these Merc 5.7's have.

[NoKlu]

Looking for info on a pair of 5.7's out of an 1990 3555 Bayliner. These are new to me and I know nothing about them but are trying to get them running and back in the boat. I'm told one should be counter rotating but they were not marked when pulled by a contractor. Just set on ground in no particular order. The first engine we got a good compression test from and the engine spun in clockwise direction. Second engine we spun up and got really bad to almost no compression. We used new starters, both for standard rotation to do the tests. Our Mechanic told us ,if we spun the counter engine, clockwise, we would get no good numbers even if was a good engine. Original starters were seized solid with rust so we couldn't spin those either. The merc dealer claims that the serial numbers on the tags are not serial numbers but another number they do not recognize. The Number is C759898. I believe this to be the counter rotating engine but I don't know how to tell for sure. Both drives were removed and the props are the same rotation. I'ts possible the drives and props, were switched out as this was a salvaged boat. Got it cheap and can put a few bucks in it to get it going. Can anyone check that serial number and tell me if that is the counter engine? I would upload the pic of the tag but it's to large a file.

 

[alldodge]

The serial number shows up as an 1987 and I'm not seeing counter rotation. If plug wires are still on the motor, check firing order

 

[Scott Danforth]

I didnt think there were any RH rotating engines used after 1985

pull the timing cover. if you have gears, its a RH rotation, if its a chain, its LH rotation. as the RH GM motors used gears (vs the chryslers)

 

[tank1949]

I have never seen or heard of a counter rotating Chevy/MC combination. Not to throw a monkey wrench into a jet engine, but I had a 1986 Sea Ray with dual 5.7s. Neither OD, nor prop, nor motor were counter rotating. I had a 79 Penn Yann that had a counter rotating Ford 351 Windsor, that was a pain in the butt until we figured how to rotate pistons 180 degrees so that oil slingers were supposed to be positioned. We kept gaulding pistons. My prevuious Proline had counter rotating ODs/props and chevy motors that were std rotation motors. My current SR has counter rotation in the ODs. I assume the gear change is in the upper part of the OD but I may be incorrect. My Bravo props are definitely pitched right and left. Both stroker motors (5.7 chevy conversions) turn clock wise if looking at harmonic balancer. Looking at flywheel, they turn counter clockwise. If your motors are all rusted up salt water motors, which rusted up starters suggest, you might consider scraping motors. Pull ODs and physically turn each drive shaft and watch prop rotations. At least this will tell you what kind of ODs you have. Good luck!

 

[matt167]

turn the crank on one, one way does not matter. note which way the distributor rotor turns. turn the other motor the same way. If the distributor turns the same way, they will be standard rotation. If one turns the other way, you do have a reverse rotating engine but it will be easy to figure out..

Motors in a 1990 boat should not have a reverse rotation engine regardless of make except inboards. It's far easier to reverse the outdrive than the motor which they eventually figured out.

 

[alldodge]

If the distributor turns the same way, they will be standard rotation

Yes, correct

 

[achris]

Serial number: 0C759898
Model: 457B100BS
Year: 1989
Description: 5.7L Alpha.

This is NOT a right hand rotation engine.

Point of fact. NO right hand rotation engines are coupler to Alpha stern drives, only inboards. If there was any 'counter rotating' then it's in the lower housing of the drive...

Chris........

 

[alldodge]

Ahhhhhhh Word

 

[NoKlu]

Thank you all for your input. We have all the Info we need to proceed with this Boat. As usual, iboats is the best boating resource on the net. I've not been on for years, but nothing has changed, only a few people.