View Poll Results: Check all that apply to you.
Have never had an engine failure in my twin engine boat. 6 17.14%
Have had one or more failures that could be fixed at sea. 17 48.57%
Have had one or more failures that couldn't be fixed at sea. 16 45.71%
Have had both engines fail at the same time, getting a single to cut my failures in half. 1 2.86%
Multiple Choice Poll. Voters: 35. You may not vote on this poll

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Old 05-22-2016, 09:22 AM   #21
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Dave, please don't take offense, but I'm not sure I'll invite you out for a trip on my boat. Your luck may rub off.

I like to think I got all of my mechanical bad luck out of the way in one big lump. I'm all set now
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Old 05-22-2016, 09:38 AM   #22
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Running on one Engine

I've had both single and twin engine boats, and in two cases was glad to have twins. One was related to a damaged prop, where I came home on one engine. The other was a belt snapped. I was able to go below and replace it, while my wife was able to pilot the boat into what was moderate seas.
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Old 05-22-2016, 09:39 AM   #23
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It appears that most diesel engine failures are fuel related, second to raw water supply.
What is the source of data for this claim? Not saying you're wrong, just want to vet the underlying data.
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Old 05-22-2016, 09:56 AM   #24
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It appears that most diesel engine failures are fuel related, second to raw water supply. A twin engine boat is no better than a single engine boat if both engines share a common fuel supply.
Fuel system vs fuel alone are very different failures. So is a plugged filter due to lack of maintenance a fuel or fuel system failure? Or how about the guy who uses 2 micron primaries and swears he is getting bad fuel because his filters plug up all the time? So many variables.

And raw water supply - know of several cases where planing boats ran hot because they were propped wrong, cooling systems were just fine though.

But the premise of the thread is that failure modes for twins vs singles are different? Most engine failure modes seem owner or bad mechanic related. Maybe it is true, twin owners are not single minded and hire stupid mechanics.
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Old 05-22-2016, 10:18 AM   #25
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I've never had an engine failure with my twins nor did I ever have a failure with my previous single. However, I did have a steering failure on my current boat with twins. I was able to drive it home by modulating throttle and gear input; I easily "steered" her home and backed her into her slip with no drama at all.
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Old 05-22-2016, 10:56 AM   #26
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I've had twins and singles. Had a gear failure on the twin, came home on the other. On the singles, never had a propulsion failure. Did have to get towed when a new rudder arm fractured, apparently a casting flaw. At the time had no provisions for backup rudder control, that has been remedied. Have had a few issues with the single engines, leaks, impellers, stupid tank management by me, etc, all easily remedied without mission failure.

I still prefer the single, even though there will remain an increased chance of needing a tow. To me the tow option is just another tool in the tool kit. Use it if you need it.

Twins will have a higher probability of having a problem, but a much lower chance of needing a tow. And that problem may ruin trip plans, whether a tow is needed or not.
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Old 05-23-2016, 12:59 PM   #27
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One of the guys in our marina had one of his big block gassers fail. He was exiting the fuel dock on his way to the marina and one engine stalled. It wouldn't re-start because the starter crapped out.
He had to get towed in. (he has trouble docking with both so he didn't dare try it on one)
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Old 05-23-2016, 07:10 PM   #28
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Lost Detroit diesel starboard engine. Spun the main bearing. Port engine got us in.
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Old 05-27-2016, 02:24 PM   #29
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what I've noticed with twins is when one goes the other is often right behind it. Even if each engine has separate everything they will still share common traits like same age, make, hours so weknesses with one are also in the other. If you wish avoid the twin engine pitfalls and seeking 2nd engine for dependability you should chuck that idea and get a single engine with a get home or wing engine or even a hybrid like the greenline. These systems will get better fuel economy and save 50% on maintenence costs as well. The greenline 33 can go 1,000 miles on 100 gallons of fuel the most economical powerboat made i think.
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Old 05-27-2016, 05:51 PM   #30
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The greenline 33 can go 1,000 miles on 100 gallons of fuel the most economical powerboat made i think.
Where do you get those numbers? On diesel, the 33 per their website has a range of 700 nm and that is on 132 gallons of diesel. On electric it has 20 nm.
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Old 05-27-2016, 06:23 PM   #31
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It would be hard to argue that two engines are not more reliable than one. Maybe much more reliable.
But is it worth the trade-off?

The risk of having unprotected props & rudders is much more difficult to assess. This risk has the potential to be much worse than just a breakdown.
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Old 05-27-2016, 06:30 PM   #32
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It would be hard to argue that two engines are not more reliable than one. Maybe much more reliable.
But is it worth the trade-off?

The risk of having unprotected props & rudders is much more difficult to assess. This risk has the potential to be much worse than just a breakdown.
I think the risk of having unprotected props and rudders is overstated. Most twin engine boats are designed with some protection and the protection singles think they have is often overrated. By not being centerline, twins gain some there as well.

As to whether the reliability of twins is worth the trade off, that's such an individual thing. We like and only have twins but I'm not going to argue for a moment against singles. We do understand that choice.
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Old 05-27-2016, 07:58 PM   #33
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Not sure most twins have some prop protection...many do, many dont....

Have owned and towed plenty of both.

Singles due to engine or fuel, twins often due to grounding and running gear issues.
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Old 05-27-2016, 10:37 PM   #34
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Where do you get those numbers? On diesel, the 33 per their website has a range of 700 nm and that is on 132 gallons of diesel. On electric it has 20 nm.
Think. The company keeps a... I think 15% safety margin in their numbers so that brings the gallon age to about 110 and then it takes the D engine about 2.5 hours to charge the batts which in pure electric can run the boat for 20nm. Gives you 700 miles on the thumper and anther 300 more or less on the silient giant<electric>. So, that makes 1,000nm per tank. I rounded to 100 gallons. I ran my numbers by greenline and they said my numbers were close to theirs if you take into consideration the use of the electric motor. Email them they will explain. If you know of any other vessel that efficient please let us know.
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Old 05-27-2016, 10:53 PM   #35
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Think. The company keeps a... I think 15% safety margin in their numbers so that brings the gallon age to about 110 and then it takes the D engine about 2.5 hours to charge the batts which in pure electric can run the boat for 20nm. Gives you 700 miles on the thumper and anther 300 more or less on the silient giant<electric>. So, that makes 1,000nm per tank. I rounded to 100 gallons. I ran my numbers by greenline and they said my numbers were close to theirs if you take into consideration the use of the electric motor. Email them they will explain. If you know of any other vessel that efficient please let us know.
Huh? Where does the fuel come from to charge the batteries?
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Old 05-27-2016, 10:56 PM   #36
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Huh? Where does the fuel come from to charge the batteries?
out of the 132 gallon tank. Then when batts are charged you turn off the diesel engine and turn on the electric and go for 20nm. Simple. The main D engine charges the batts in conjunction with solar cells of the roof during the day giving even more range than what you would achieve at night when you would have to rely totally on the D engine to charge and propell your boat
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Old 05-27-2016, 11:07 PM   #37
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out of the 132 gallon tank. Then when batts are charged you turn off the diesel engine and turn on the electric and go for 20nm. Simple. The main D engine charges the batts in conjunction with solar cells of the roof during the day giving even more range than what you would achieve at night when you would have to rely totally on the D engine to charge and propell your boat
I expect the advertised range of 700nm is running purely on diesel since that is the most efficient. Charging batteries then running them down via an electric motor is less efficient that just running the diesel to turn the prop directly. If the boat could go 1000 miles on a tank as you describe, why wouldn't the company advertise that?
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Old 05-27-2016, 11:18 PM   #38
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I expect the advertised range of 700nm is running purely on diesel since that is the most efficient. Charging batteries then running them down via an electric motor is less efficient that just running the diesel to turn the prop directly. If the boat could go 1000 miles on a tank as you describe, why wouldn't the company advertise that?
The electric motor is more efficient than the d you have it backwards. They are conservative and state a 700nm range on the 33 because the hybrid system is an option and not standard. D engine only you get 700nm range.But if you opt for the hybrid option you have the option of running on pure electric which gives you an aditional 20nm range before batts need recharging., Takes 2.5 hours to recharge the batts via d engine alone. During the day with the sun shining you have the roof mounted 11kw solar pANELS ALSO CHARGING THE BATTERIES SO MY NUMBERS ARE CONSERVATIVE ALSO BECAUSE I DIDNT FACTOR IN THE SOLAR INPUT JUST USED THE FACTORy NUMBERS FOR engine generator charging. opps cap lock. sorry I wasnt shouting on most of my computers i have removed that dumb key.
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Old 05-27-2016, 11:22 PM   #39
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Back to the original question....

Happened to me twice. Once with an old gas-powered twin express cruiser (sorry!) a water pump seal failed. Got back to a harbour on the other engine.

Another time on the trawler with an transmission oil pump leak that drained all the oil. I could have locked the transmission and got home, but easier to simply get to safe anchorage on one and fix it there. Docking/anchoring on a single with a locked transmission would have been 'entertaining'.
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Old 05-28-2016, 12:31 AM   #40
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Back to the original question....

Happened to me twice. Once with an old gas-powered twin express cruiser (sorry!) a water pump seal failed. Got back to a harbour on the other engine.

Another time on the trawler with an transmission oil pump leak that drained all the oil. I could have locked the transmission and got home, but easier to simply get to safe anchorage on one and fix it there. Docking/anchoring on a single with a locked transmission would have been 'entertaining'.
That's true. But as you said you could have locked it and got home so in that case a single would have been fine. A water pump seal failure would have put water in the bilge but you could have still used it if you had to right?

failure with twins will always be twice as frequent as with a single. I had a power steering hose split on a brand new boat with less than thirty hours one time. Boy did that make a mess but a fellow boater lent a hand and we improvised allowing the steering to function till i made port and called the dealer. Lucky it was in the bay
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