engine rotation

[brian4190]

i am posting this for overspray a forum member that is having technical problems posting. he is doing a complete bottom up restoration of a mid sixties 28' sportfisherman. he is ready to drop in his engines and noticed that they were peviously set up the opposite (starboard engine counterclockwise rotation) than is standard. (mine is set up in the standard configuration) as mine has been repowered along the way he just wannted to double check with the braintrust at the forum if anyone has any knowlege if hatteras could have set the boat up that way originally due to some handleing issue or was this a previous repower instillation mistake. he has contacted hatteras and they did not know.

 

[Trojan]

I do not think he wants to have them that way. If I remember correctly that rotation will cause ill handling, steering problems and Starboard to port-side boat balance when on plane. Prop tip wash and rise will be centered in the center of the hull causing all type of turbulence and lift. Causing a teeter totter effect side to side. He needs to check and ask them why they are doing it that way. Maybe there is a secret reason. I could be wrong. Ever see a boat with twin rotation motors. I sold a 1960 32ft Owens to a gent that trashed a motor right after buying and he replaced it with the same rotation motor. Then tried to tell me the boat was screw up. Yeah! It ran at about a 30 degree list on plane and would not steer. There is a tremendous amount of lift and tip thrust from the prop. Where is that twin lift going in a reverse rotation? I could be wrong.


BILL

 

[Avenger]

Engine rotation is not the key, it's propellor rotation. Stbd prop should turn clockwise when facing the bow and the port prop turns counterclockwise. You probably already know that, but from your post it's not 100% clear. Install the engines so that the props rotate correctly and you'll avoid quirky handling probelms when docking. I think Seawise had a boat that was set up backwards and there were issues. If you do a search you should be able to find the thread.

 

[Trojan]

Your correct. On some setups the transmission is just reversed and the motors run the same. I was thinking it was straight through. Old school. He didn't present all the info. See I said I might be wrong. LOL He needs to check the props and the type transmission. That will work. I just need to have that 2 cups of coffee before I start posting.

BILL

 

[drburke]

...I just need to have that 2 cups of coffee before I start posting...

Just two? I need at least four, and wind up spilling most of the first!

DAN

 

[ELECTRA VI]

Years ago,my grandfather purchased a 33' Striker with props that turned the same direction. He only kept it four months.
George

 

[Fanfare]

I have always heard that it is prop rotation that is critical. But I have never driven a boat rigged backwards. How did this boat handle before the overhaul?

My original 8-71 naturals were opposite rotation. That gives perfect torque cancellation. I have also been told that it was necessary because the Allison transmissions could only handle sustained full power in forward, not in reverse. When I re-engined a few years ago with 6-92TAs Detroit Diesel no longer made the countra-rotating engines, as the new Twin Disc transmissions could take full power in either direction. One essentially runs in forward, the other in reverse. This should, in theory, give a torque imbalance but I have noticed no difference in operating the boat. She seems to track just as straight as ever. The props, of course, do go in opposite directions.

 

[Avenger]

See I said I might be wrong.

I wasn't trying to correct you. You just got your post up before I finished editing mine. Yes, I type slow. Maybe some caffeine would help.

BTW here's the thread I was talking about:

http://www.samsmarine.com/forums/showthread.php?t=1926

 

[Trojan]

With a symmetrical built transmission. There are no property changes for direction. Input torque and rotation should not matter. The final output from the trans does not care what the input is doing other than what direction am I going.

BILL

 

[BUSTER]

i am posting this for overspray a forum member that is having technical problems posting. he is doing a complete bottom up restoration of a mid sixties 28' sportfisherman. he is ready to drop in his engines and noticed that they were peviously set up the opposite (starboard engine counterclockwise rotation) than is standard. (mine is set up in the standard configuration) as mine has been repowered along the way he just wannted to double check with the braintrust at the forum if anyone has any knowlege if hatteras could have set the boat up that way originally due to some handleing issue or was this a previous repower instillation mistake. he has contacted hatteras and they did not know.

Is this a situation where someone may have had B-W velvetdrive trans,@ 1:91 to 1 ratio and gotten mixed up? That particular trans,with that ratio can cause a lot of problems for a novice mechanic,as the trans,turns opposite of the engine. Getting either the engines mixed-up or the trans, mixed-up makes for incorrect propeller rotation.

 

[TedZ]

We have been through this and i'm sure there are many positions and opinions. Mine is that most boats props turn outward when viewed from the stern i.e. port CCW, stbd CW. Turning the props inward could possibly improve performance as there are no absolutes in hydro dynamics. It simply depends. Easy to try if you have symetrical trannys. Let us know. Speed? Handling? Doubtful there will be much difference as long as both props are not spinning the same direction.

Ted

 

[krush]

I think in some high performance applications (go fast boats) sometimes it's benficial to turn inboard instead of outboard.

 

[Capt Mike]

In high performance boats the rotation will lift or lower the stern as she rides, I don't know if it will make any difference on these boats.
Mike

 

[OVERSPRAY]

Hey guys, Finally got in. Thanks for the info, After carefull and thorough research, it is in fact the 1.91 ratio B/W gearboxes that counter the shafts. When I bought my boat it was on the trailer and the props were off, I just finally got the first motor assembled and couldn't figure for the life of me why the starboard motor was the standard rotation. apparently the 1.91 is the only trans in that series that counters the engine, after a little research on model/serial# the truth came out. the only thing that signifies the counter gearbox is a (*) after the model# on the tag, Thanks brian for posting for me, and thanks guys for the replies. If the gallery works I'll be posting a load of new picks, all exterior finish work is complete and I'm starting to rig the powertrain. this thing is comin out SWEET!!!

 

[Boatsb]

Just an FYI. The 1.91 and the 2.1 have been used when engines are only available in a standard rotation.

 

[REBrueckner]

Stop it guys!!!!...now I'm confused....I'm pretty sure my 48 YF props turn in at the top...CCW on stb and CW on port....Now I have to go check my diagram next time aboard.

I never thought there was much difference as long port and stb props turned opposite rorations.

Over the hill and gaining speed.....