Running on one Engine

J

jmas

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34 Ft Express Fish, Twin 454 inboards.
Having starboard engine removed for exchange or rebuild. May move the boat on 1 engine a few times.
Would removing the Starboard Prop until new engine is replaced, help maneuverability or would it make little difference?.
 
The question is if you removed the trans with the engine. If not, I have read warnings about allowing the shaft to spin for a long period on its own. Otherwise, I would think removing the prop would be better. It will be hard enough to run on one engine as it is. I certainly wouldn't run it at cruising speed or expect your boat to plane.
 
I would think removing the unused prop would very considerably reduce detrimental drag on that side but maneuvering safely could still be quite a chore since on most I/B's the props are more widely separated than say T/O/B's. However, I have not tried it with 1 prop removed.

A few other considerations:
Will you be removing the transmission too ? Even if you leave the tranny in, a free-wheeling prop could conceivably cause problems on a transmission held on by just 2 aft motor mounts and only blocked forward. There could potentially be even bigger problems if steering difficulty resulted in the dead prop grounding or fetching up a mooring line or similar and getting yanked.

Hopefully you have plenty of experience maneuvering your boat in close quarters with one engine off and are comfy with that, as I expect you are. My T/I/B boat is just 27'and the gas engine small rudders and props make for voluminous stomach acid production attempting that in tight channels and through mooring fields and backing on serpentine track into my slip behind a tee and inboard of 2 spiles. That is with the dead engine in place... But prop on.) Unfortunately, at various times over the years, I have had to travel short and long distances with one engine down in up to 40 kt winds in open water with big seas and into tight rocky channels and crowded harbors and if I never have to do any of that again that would be pretty fine with me. However, if you feel you need to , deploying down only the trim tab on the running engine side can help balance steering a little .

Keep in mind , you have to build up STW with that 1 usable prop far to one side of the centerline before the boat will respond to water pressure on the rudders. Just beginning to move in forward gear, the boat will always steer way to the opposite side of the running engine (no matter the rudder angle) until sufficient STW is attained.

You can block the exhaust hoses ( I do that with large PVC pipe caps hose clamped inside the hoses when replacing elbow/risers), but... if... the transmission is removed, and unless you have more than one strut on each side , it may be difficult to secure the propshaft in good enough alignment to prevent the packing gland or particularly any dripless seal from leaking badly if moving the boat in the water.
This begs the question, why not play it safe and keep the boat hauled until the job is done?
 
Tranny will come out with Engine.

"deploying down only the trim tab on the running engine side can help balance steering a little" .
Sounds like a plan, I will try it.

2 Grandsons visiting from Utah, Makes it hard to stay at Dock.
 
Trim tabs don't really produce much drag at or below hull speed, and any drag is over come by the engine thrust anyway. I don't get it...

You will need to lock the shaft and make sure it is supported so that the stuffing box doesn't leak. I really would not try this.

Single engine operation is ok under way but requires some serious skills In close quarters. I wouldn't try leaving the dock on one engine
 
quote:
Originally posted by PascalG

Trim tabs don't really produce much drag at or below hull speed, and any drag is over come by the engine thrust anyway. I don't get it...

You will need to lock the shaft and make sure it is supported so that the stuffing box doesn't leak. I really would not try this.

Single engine operation is ok under way but requires some serious skills In close quarters. I wouldn't try leaving the dock on one engine

Click to expand...


Pascal - putting that only that tab down and fully retracting the other allows me to goose the throttle up maybe 1 1/2 kts ( to around 7 kts if I push it ) and still maintain any steerage .That's a big difference on a long slog home.

I don't get it either, but somehow (on my boat) that drag just barely stops the boat from turning away at the "higher" speed as it does without tab extension. Perhaps the higher RPM's greater prop wash and higher STW has enough greater effect on the rudder to just overcome increased drag and 1 prop -steering torque. More likely just good voodoo though.

Just another mention - on-the-bow or-beam wind and seas can really up the steering difficulty and stomach acid production .

I've been on diesel boats with larger rudders and props that handled waay better with an engine down.

And locking down a prop shaft with prop on it for moving on one engine , without scoring damage to the shaft or seal, is not as easy as it sounds. There is a lot of torque on the shaft. If the boat really has to be moved there has to be a lot less drag without the prop, spinning or locked down.

Unless this is impossible, I would leave the boat on the hard where the engine is to be pulled and replaced.
 
When we go out for tuna on a friends boat with twin OB's, he raises one OB and troll 5-7 knts quite economically though there isn't a lot of maneuvering going on.
 
There is also weight difference. Boat by me had engine removed and boat was listing to a point where thru hulls were almost under water.

Bad idea. Rent a boat!
 
I would remove the prop, properly support the tranny and try it on a calm day. You may find it handles better than you thought it would. Or not. :-)

But you'll never know if you don't try. Just have an extra hand on board with lines and fenders ready.
 
quote:
Originally posted by jtybt15

When we go out for tuna on a friends boat with twin OB's, he raises one OB and troll 5-7 knts quite economically though there isn't a lot of maneuvering going on.

Click to expand...

Outboards vector thrust so are more effective at low speed and tend to be mounter closer together. I/B have rudders that need flow to be effective. Outboards are also a million times better steering in reverse.
 
something must be done to stop the shaft from sliding back and hitting the rudder since they are tied together.
Stability will be terrible and flipping the boat a possibility.
I have done some single engine operation without trouble but that was with the engine installed. Speed must be kept to minimum to allow steering. Turning toward the running engine will probably be hard for docking backing and filling may be needed.. Perhaps easier if the other prop were off. But making a 270 degree turn might be best. You will have a very unbalanced single engine boat. At very slow speeds,5 kts, I don't think you would have too much trouble keeping a course.
Backing will be similar to a single engine boat with small rudder, hard with little control of the bow in and wind.

In conclusion I might doo this in calm conditions in protected areas fro short distances if the boat had to be moved for some reason, certainly not a pleasure trip.

Why not use your towing insurance??
 
Boat would only be moved while both engines are still in Boat.Shaft will stay connected to bad engine but Prop would be removed.
Once bad engine and tranny is removed, boat will stay at dock while rusty mounting brackets are replaced and Bilge is cleaned and painted.
Hoping Port engine keeps running good.
Both engines installed 1995 and have 1250(FUN) hrs.
 
Joe- That sounds a bit better. Does the bad engine start and run at all? If it does and the prop stays on you might be able to run it very briefly just when tight- maneuvering for a more welcome margin of safety.
If it does not run at all, and you really have to move it under it's own power, then I'd agree -remove the prop and light a candle.
 
That is much simpler. Steering as above will be awkward but do able. backing into a slip will require small rudder single handing skills, again do able. Just pick calm weather and have help. If necessary just get near the slip and toss lines to warp it in. No worries from me .
 
Sandy-Bad engine cannot be run.
Bruce-I'm confident I will be OK.

Will keep all suggestions in mind, and post results when engine is out and Boat is back at Slip.

Thanks all.
 
Joe,

I once had to single engine all the way from Elliott Key to Dania. Not by choice. I won't say it was fun, and it was a long slow ride, but definitely do-able. Backing into my slip was less than fun, but fortunately a friend was at the marina and helped out.
 
I had a similar issue at the beginning of the year. We have an annual "last day of school" cruise for my kids and their friends. My port engine had a blown head gaskette. My dripless has a tube from one shaft to the other so both should be lubricated. However, I was able to turn engine on for a few minutes around dock leaving and coming so nobody noticed the missing engine as we limped to the anchorage.

Good luck and don't forget you can always nose into your slip bow first (at least that was my plan if need be)
 
I ran pretty much all of July & August 2013 on one motor. Well 'ran' is a stretch, because I left the slip four times - three to anchor across the channel from the marina and one longer ride of about 10 miles for winter storage. I didn't bother removing the prop - for me getting out of the slip was more of a hassle than backing in. It was port motor for me - so to back in I just laid it up against the port side pilings on the next slip, and used the SB engine to nudge her back in - with some pushing off the pilings to get the bow back out where it needed to be. The turn to get out required a bit more speed than I was used to using to leave the slip, but still not a big deal as I got lucky with low winds on the days we went out. I also had the advantage that I could have started the bad motor and ran it on 7 cylinders if the **** hit the fan, which gave some piece of mind but wasn't really needed.
 
I had a 32' twin diesel express sportfish and had to come in on one engine a couple times. In close quarters it's not easy maneuvering but I managed. In any kind of wind or if you had to stop in a narrow canal or marina due to boat traffic it could be an issue because once you lose momentum when you go back in gear the boat wants to turn. I run my current boat (38' twin diesels) on one engine all the time in my canal to keep to a reasonable no wake speed, but I typically start with both in gear to get some momentum going and then take the port engine out of gear and turn the wheel to compensate.
 
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