Run on one engine?

Highliner

Highliner

Active Member
Apr 15, 2020
163
Lake Erie
Boat Info
2002 Sundancer 320
Engines
5.7L MPI w/V Drives
Hi all,

We have a fairly lengthy (350 mi) trip over the water coming up. When traversing from one port to another I sometimes prefer to slow things down and putt along at hull speed rather than cruising on plane the entire duration. The wind in your hair feeling is great and all, but sometimes a more relaxing ride really makes a nice day on the water.

Wondering if anyone ever runs on one engine at hull speed to save some fuel and cut engine hours in half in this scenario? We are travelling in a 320DA.
 
Just went through an exhausting discussion about 1 engine running with three different people. Boat manufacturer regarding shaft seals, engine (MTU), and a transmission person.

This applies to my boat and I feel comfortable with the quality of the information. Does not necessarily apply to your boat.

Transmission- engine should remain on, in neutral, at idle. Transmission oil pump is driven off engine. Should engine be disabled, 5-6 miles at low speed is probably ok, any more, secure the shaft from turning.

Shaft seals. Yes there are cooling lines which are intended to pump water to each seal. However my manufacturer had a lawsuit over one engine not secured which resulted with water ingestion. Their recommendation, 5-6 miles at low speed, or secure the shaft. The water ingestion was a bigger concern than the shaft seals.

I realize your question was about just running on one engine. You didn’t say what kind of drive system, or if you were thinking about shutting one engine off.

Just sharing my findings, maybe it will spur some thoughts.

When running on one engine, there are, or may be, other factors to think about.
 
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Highliner said:
Hi all,

We have a fairly lengthy (350 mi) trip over the water coming up. When traversing from one port to another I sometimes prefer to slow things down and putt along at hull speed rather than cruising on plane the entire duration. The wind in your hair feeling is great and all, but sometimes a more relaxing ride really makes a nice day on the water.

Wondering if anyone ever runs on one engine at hull speed to save some fuel and cut engine hours in half in this scenario? We are travelling in a 320DA.
Click to expand...

I often slow it down and run at ~10mph, but on two engines. I sit on the bow with the auto pilot remote and smoke a cigar.
 
FootballFan said:
I realize your question was about just running on one engine. You didn’t say what kind of drive system, or if you were thinking about shutting one engine off.

Just sharing my findings, maybe it will spur some thoughts.

When running on one engine, there are, or may be, other factors to think about.
Click to expand...

Interesting. It's a V Drive boat with Tides shaft seals. It does have the crossover water feeds so that each engine should, at least theoretically, feed both seals.

My plan was originally to shut the second engine down. I assume just leaving the transmission in gear is not enough to prevent it from turning at low speed? Securing the shaft doesnt seem like a simple thing to do.

Do you know the cause of the water ingestion? the only thing I can think of would be from the through hull "scooping" water while underway but I wouldnt have expected enough pressure to cause damage at 5-7 knots.
 
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Having lost an engine due to an alternator failure in a 340DA I can tell you this:

1) It sucks!
2) It is hard to steer straight as the single engine is not on centerline and wants to push the bow towards the opposite side. So you weave trying to get somewhere.
3) Did I mention that it sucks?
4) Plan on 5 or 6 knots... less if you have some seas and maybe 7 if it is calm.
5) And then there are the possible transmission and seal issues the @FootballFan mentioned.
6) #2 can be easier if you have an Autopilot. My 340DA wasn't equipped with one.
7) SO it sucked for 5 hours at 5 knots for 30 miles... weaving like a drunken sailor...
 
I'd be interested to see if you actually save fuel on one engine? I've done it once due to a broken shaft seal. It was not an ideal, relaxing scenario. I didn't run the autopilot just because I was so amped up for the 5 +/- miles I had to drive. But man that rudder is hard over to keep the boat moving straight on a single. And making typical cocktail speeds on one engine works that running engine pretty hard.

It sounds interesting on paper but in reality it's likely not as relaxing as you might think, OP. Go out and try it for a few miles for kicks. And hey - good practice is to then bring her into port and dock it on one. That's where the rubber really meets the road (or the rub rail?) :)
 
My ocd prevents me from doing it. Like to keep those hours the same:) I would run it in gear in a emergency. 6 knots max.
 
For you guys with twin tanks and a genny hooked up to one tank, does it also drive you crazy if one tank goes down faster than the other? o_O
 
Phil S said:
For you guys with twin tanks and a genny hooked up to one tank, does it also drive you crazy if one tank goes down faster than the other? o_O
Click to expand...

And that's why there is a fuel manifold to choose which tank to draw from. It's hard to remember when your having a good time to switch the fuel draw on the generator, so I just alternate weekends. I often have an imbalance with the tanks, but I try to keep it under 10 gallons, more to the 5 gal. mark. If the tanks get too far out of balance, I either fuel up more on that side or switch so both engines are off of that tank for a short time.
 
Our home was on a long narrow lake and 45 minutes from Lake Michigan at slow no wake speed. We boated 3-5 days a week so the potential was there to really pile up hours on the meter. We putzed around the lake a lot so always on one engine to keep the hours down with an eye to preserving the resale value of the boat. Never had an issue with either the 37SR Express or the Tiara 32 Open. I alternated the engine used to keep hours similar.
 
SKybolt said:
And that's why there is a fuel manifold to choose which tank to draw from. It's hard to remember when your having a good time to switch the fuel draw on the generator, so I just alternate weekends. I often have an imbalance with the tanks, but I try to keep it under 10 gallons, more to the 5 gal. mark. If the tanks get too far out of balance, I either fuel up more on that side or switch so both engines are off of that tank for a short time.
Click to expand...
I am both jealous that I don't have this feature on my boat, and also happy that there isn't yet another part that I have to keep an eye on. :)
 
I don't see the cost/benefit ratio to running on one regularly. Even with the cost of fuel what it is today the savings would be minimal and fuel is still a small expense when compared to the rest of the expenses of boat ownership. I would give it a try to find out for yourself and determine if cruising on one is enjoyable and trouble free for your situation. My guess is that you would be best to just pull them both back to just above idle and enjoy the ride with the peace of mind of better handling. I once ran my 280 SunDancer 15 miles downriver on one due to a broken drive shaft. It was the longest 5 hours I ever spent on the boat!
CD
 
FootballFan said:
... Transmission- engine should remain on, in neutral, at idle. Transmission oil pump is driven off engine. Should engine be disabled, 5-6 miles at low speed is probably ok, any more, secure the shaft from turning.

Shaft seals. Yes there are cooling lines which are intended to pump water to each seal. However my manufacturer had a lawsuit over one engine not secured which resulted with water ingestion. Their recommendation, 5-6 miles at low speed, or secure the shaft. The water ingestion was a bigger concern than the shaft seals. ...
Click to expand...

This is spot on. TBH, if your going to run on one engine, leave the other at idle and in neutral. The shaft seals will be toast otherwise, and when they go hopefully you won't be on the boat sinking in the middle of the night.
 
Carpediem44DB said:
I don't see the cost/benefit ratio to running on one regularly. Even with the cost of fuel what it is today the savings would be minimal and fuel is still a small expense when compared to the rest of the expenses of boat ownership. I would give it a try to find out for yourself and determine if cruising on one is enjoyable and trouble free for your situation. My guess is that you would be best to just pull them both back to just above idle and enjoy the ride with the peace of mind of better handling. I once ran my 280 SunDancer 15 miles downriver on one due to a broken drive shaft. It was the longest 5 hours I ever spent on the boat!
CD
Click to expand...
If you boat a lot, you halve the hours on the meter when sight seeing at slow, no wake speeds. Like it or not, high hour boats are valued less in the market. This is a bigger factor than fuel costs which I agree amount to little in the overall cost of boating.
 
SKybolt said:
This is spot on. TBH, if your going to run on one engine, leave the other at idle and in neutral. The shaft seals will be toast otherwise, and when they go hopefully you won't be on the boat sinking in the middle of the night.
Click to expand...
So I just had my boat towed about 8 miles with both motors unable to start. If I find a leak around the shafts what is the repair going to look like?
 
I had my 44 towed 25 miles and due to dead batteries we were towing with both engines shut down. I had tides seals and after ten miles with no cooling water, the port seal seized on the shaft and tore the boot! I went from a boat being towed with just damaged props and minor hull damage to a boat taking on water with 15 miles to go! I had been running the genny the whole time so by then the batts were up enough to start the mains and at least provide cooling to the seals for the remainder of the trip. Got new shaft seals assemblies, courtesy of the insurance company.
In your case I would inspect the seals very carefully before you splash.
CD
 
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