Right Rotating Prop with Propeller Shaft Offset to Starboard

[Bets]

I'm interested in buying a Sabre 30 and it has been repowered from a Volvo to a Yanmar 3GM. The propeller shaft is to starboard of the keel and the engine is right rotating. What are the handling issues?

[boasun]

When going ahead you may need (or not) a hair of right rudder. When backing down, once you have sternway on you will need 5 or more degrees of right rudder.
You didn't state if the propeller is right or left hand. This minor detail makes a difference in how you handle your vessel also.
The engine could be right rotating and the tranny may be reversing it... a detail that very seldom happens but it has a time or two.

[Dockhead]

It will kick to port in astern.

[Bets]

Thanks! The engine is right rotating and the propeller is right hand

[never monday]

Originally Posted by Bets

Thanks! The engine is right rotating and the propeller is right hand

installing a left rotation propeller on that gear box is not recommended. This will put the box in reverse to go forward. The counter gear that allows reverse. Is located in the upper section of the box away from the splash oiling.

[Bets]

No one ever said reverse was easy on a sailboat, and this edgy engine situation just seems to complicate the matter. Given the overall neglect this boat has received, which will cost about 10K and elbow grease and comments I've received here and from Sabre's tech on the engine, I should probably cut my losses and walk away from this deal having just invested the cost of a survey.

[David M]

You won't notice any difference going ahead. It will back to port going astern like most single screw boats with a right hand propeller backing. No change is necessary.

[Bets]

Thanks, David. I'm so on the fence with this boat.

[Bets]

David M, wouldn't there be additional prop walk to port if the propeller shaft is not centered but actually slightly off center and to starboard? That is the case with Sabre sailing vessels - the propeller shaft is off center and typically is the opposite side from the rotation of the propeller. Seems this boat would be more challenging in reverse with more forceful prop walk to port.

[Captain Lee]

Reading this in 2015. Don't know if Bets ever bet on that Sabre, but thought continuing the discussion might be worthwhile for others interested in offset shafts. I have an Erikson 35 with a right hand prop, mid-cabin engine, with shaft angled a few degrees towards starboard quarter.

I agree with David M and Boasun here. There seems to be little important difference in handling in either forward or reverse.

I find that I disagree with Bets' conclusions. Prop walk to port in reverse will be less, not more. Do a mental experiment: Imagine a shaft offset by 30 degrees, and long, so that the prop is way back under the far starboard quarter of the boat. Backing this boat down will definitely move this boat's stern to starboard (forgetting rudder effects for the moment). In the actual situation we are discussing here, the same tendency is present, but it is slight, and only slightly counteracts the "port propwalk in reverse" that all boats with right handed screws have.

As far as the shaft being offset to the wrong side when going forward, adding additional rightward turn to the existing bow turn to starboard from port propwalk, I would submit that 99% of the steering concerns that skippers have relate to backing down. I can't recall ever hearing someone complain about not being able to steer while going forward. I think Bets' concern here about shaft offset to the wrong side is theoretically correct, but has no real-world importance.

As for me, when I'm backing down uncontrollably to port like the rest of you, I do always get a small sense of satisfaction: "At least my boat designer made some attempt to offset this problem."