Single or Twins?

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maineman

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Hi everyone,

I know this has been discussed here at length before. BUT I'm just about to make an offer on one of two almost identical trawlers and I just need a little assistance clarifying my thoughts before parting with my hard-earned cash.

2007 Mainship 34 Trawlers. One with a single Yanmar 315 hp with 1,450 hrs. The other has twin Yanmar 240 hp engines with 800 hours on them.

We'll use them in BC and Alaska. We are old farts and tend to poke along at 6 - 8 knots.

Any thoughts on relative quality of either engine, dependability, fuel efficiency, maneuverability, security, maintenance costs and any other etceteras are very welcome.

Thank you all for your very valued advice,
Ron
 
As you mentioned, much has been written on this topic. I'd suggest searching out some past threads. All the issues and arguments remain the same. Only the intensity of the comments changes.
 
There is much to be learned from prior discussions of this topic, although the gist seems to be that the single engine guys wouldn't have it any other way, and the same is true for the twin owners.

You bring up a slightly different question, however, by introducing the 315 hp Yanmar vs 240hp Yanmar question. I don't know much about Yanmars, but I believe they are "high rpm" engines, which generally translates to reduced reliability (though I am sure many will argue, maybe correctly, otherwise) as compared to a lower rpm engine. To the extent that is true, I would think that the argument in favor of twins, based on redundancy, becomes stronger.
 
Even being a die hard single guy...most of the time....yesterday, wished I had twins for the first time in 50 years of boating.

Just for convenience though, not safety.
 
psneeld said:
Even being a die hard single guy...most of the time....yesterday, wished I had twins for the first time in 50 years of boating..
Click to expand...
Why? What happened yesterday? :blush:
 
Make a List

Make a list, in writing, of the pluses and minuses of the 2(?3:)) engines, using your own thoughts and the thoughts of others posted here which you find helpful. You might visualize it without writing it down, but I find a list, on screen or paper,very useful.
Leaving aside the characteristics of the 315 vs 240 which others will know and post about,(is the 315 simply a higher output version of the 240?)you might be balancing things like redundancy, maintenance service costs,accessibility, reliability, fuel use, longevity, noise levels, simplicity, speed when required, maneuverability, the need or not for thrusters one or both ends and all that entails, etc.
I`m thinking either will be a fine boat, it`s a question of choosing best.There may be aspects of each boat to factor in, I`m sure you have that under control.
 
I've been on Mainships with singles and with twins. Problem with the twins is on that boat the engines are cramped as hell. Access difficult.

If you want the twins, make sure you can put two hands on every part of the engines. Both sides and front and back. If you can't, I'd call it a no go.
 
I'm a pretty diehard singles guy. That said, if you're going to remote areas that don't have Seatow or Tow BoatUS, there is a case to be made for twins or a get home alternative.

If you're going to be poking along at 6 to 8 knots, don't think it matters much which of the engines you have. Before you make your choice, see if you can work on the hull side of each of the twin engines.

Ted
 
I think that Ski's comments are the most important. I am 59 years old, 6'2", 190 lbs. My ER isn't bad but I always could use more room in the ER. If the twins restrict that too much, it would make routine inspection and maintenance much more of the pain in the backside, plus you have to do it twice.

Disclaimer: I have never owned a twin engine boat.

Good luck with the decision.
 
I have twin SP225 Lehmans in my boat. I like the the handling with twins, but working on the water pump impeller on the starboard engine last week made me wish I only had a single. Finally found a way to change it, but on a single it would have been a piece of cake. I would look very closely as to the workability around the twin engines. We looked at a 390 Mainship with twins and did not want to work on them. Not sure how much difference there is between a 390 and a 34. I think that I would opt for a single with bow and stern thrusters and would then have excellent handling.
 
MYTraveler wrote that high rpm engines have reduced reliability. Not noticeably so IMO. Reduced longevity probably so in many (perhaps most) cases but I think reliability basically has nothing to do w engine speed. And you're a rare skipper if you can put enough hours on these engines to wear them out .. high rpm or low.
 
For that boat, with a single I'd add a thruster. Those are relatively light boats with small rudders - put an oxygen tent on there for the PNW and its going to be hard to maneuver on occasion. I'd put the money into an awesome tender that could - if it had to - tow the vessel. And tow the tender.
 
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maineman said:
Hi everyone,

I know this has been discussed here at length before. BUT I'm just about to make an offer on one of two almost identical trawlers and I just need a little assistance clarifying my thoughts before parting with my hard-earned cash.

2007 Mainship 34 Trawlers. One with a single Yanmar 315 hp with 1,450 hrs. The other has twin Yanmar 240 hp engines with 800 hours on them.

We'll use them in BC and Alaska. We are old farts and tend to poke along at 6 - 8 knots.

Any thoughts on relative quality of either engine, dependability, fuel efficiency, maneuverability, security, maintenance costs and any other etceteras are very welcome.

Thank you all for your very valued advice,
Ron
Click to expand...

Taking into account what everyone else posting on here has said, realistically are you intending to do all the engine maintenance..? If not then the access is perhaps less of an issue, (mechanics tend to be younger and more supple), and the get-home on one redundancy, (thinking of where you will be cruising), plus extra speed potential and much easier manoeuvrability, might well win the day for the twins, especially as they have half the engine hours on them. Depending, of course on whether the condition, layout, and price difference are significant factors, and that is coming from one who has only ever owned a single. It might save the cost of installing thrusters, eg. Maybe they both have these, but you don't mention that. I manage without, even with a single, but I have been doing it for a long time. If I had the money I would have one if buying a single much newer, but with twin engines, probably not..? If it had one though - all the better.
 
Single screws have a fine chime, keel and rudder that protects the prop. Twins are tricky. Study your needs and the design...
 
Lucky Chucky said:
Single screws have a fine chime, keel and rudder that protects the prop. Twins are tricky. Study your needs and the design...
Click to expand...

I've never really thought of a rudder protecting a prop, but I guess if I had to lose one or the other I'd save the propulsion and Macgyver something up to steer with like a drogue.
 
refugio said:
I've never really thought of a rudder protecting a prop, but I guess if I had to lose one or the other I'd save the propulsion and Macgyver something up to steer with like a drogue.
Click to expand...

I suppose in reverse, the rudder would protect the prop, but I think what he meant is, the combined set-up of aft part of the skeg, the foot, and the rudder shaft, protect the prop because it is in between them.
 

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I think that the idea of a single prop being protected by the keel and rudder may be a bit overblown. We have twins and a deep keel. Coming up the Hudson and Erie Canal last spring there was a huge amount of debris in the water. We were very diligent in looking out for the debris, but much of it was submerged. We had 20+ hard strikes. By saying hard, I mean ones that we could definitely feel on the flybridge. I was sure that we had damaged one or both props. We even had a haul scheduled after the Trent Severn but when we went through Big Chute the lockmaster went under the boat and checked the props. He said they looked OK. So we cancelled the haul out. When we hauled for the winter, I inspected the props and found zero damage. I guess that our keel was enough protection. After this experience I am ambivalent about single vs twin in regards to prop protection. I would definately agree with the idea that if you are doing your own maintenance that a single wins vs twins due to access.
 
If you want the speed, then I would go with the twins. If you feel you need the redundancy, go for the twins. Otherwise, I would go single. Another thing is the condition of the boat. If one is in significantly better condition or better equipped, I would throw the engine debate out and just get the best boat. I have owned those 4LHAs before and they are excellent engines. Many even say one of the best engines Yanmar has ever made. Go for the best boat....and I would lean toward single if speed is not desired. That 315hp would barely get that boat up on plane and it would take everything it has to keep it there.
 
Are there other significant differences in the boats ? Are they the same price ? I'm assuming the twin engine boat is in better shape due to the lower hours....but that may not be the case. Are the other major options the same ? Heat, A/C, Generator, Electronics, Autopilot, maintenance history, etc ? Have they both been surveyed ? Does either need to be shipped ? The decision probably should involve more factors then just the engines
 
You guys are amazing! Thank you for all of this input. I'm not sure if I have been swayed one way or the other yet but it helps knowing that we all wrestle with this stuff.

MYTraveler brings up an interesting point--high rev engines vs. slower turning ones. I thought all newish (maybe 2005 and newer) engines were higher revving and higher temp than the older models to meet pollution requirements. Is this not the case? Is it still possible to buy a new, clean lower rpm engine?

And the concern regarding engine room access is very valid. I currently do all of my own routine maintenance. But anything that requires any real mechanical skill will have to be left to a professional. So, is engine room still a priority or are mechanics able to make the impossible possible?

One more question: If one of the twins does poop out, how does a boat handle on only one engine?
 
maineman said:
Do those of you with twins run on only one engine when traveling very slowly?
Click to expand...
From previous postings, most don`t. But you could, whether the gearbox is happy is a consideration.
As to the handling on one engine, you can balance the turning force with some rudder, quite easily. But docking, threading your way through moorings, things like that, are going to be unaccustomed experiences, probably difficult, and harder than a single engine boat, as the one engine and its rudder are off center. And, you`d be used to the huge plus of twins, being able to steer the boat, fwd or back, on the gears and throttles.
I`ve had a single, now have twins, I`d be reluctant to go back, even with thrusters both ends. Weigh it up for yourself but imo,if the boat with twins is otherwise good,take it.
 
Let's not get into a discussion on whether high revving engines are more or less reliable. We could go on and on and it still would not help you in this decision. I have a buddy with a Viking with twin 2400hp MTUs that have a redline of 2300RPM...if you get my drift. Let's just say that either of those engines in those boats will serve you well. My boat I have now is my first twin engine boat. I still think I am a single engine guy...but I like speed. If it were me in your shoes, I would take the twin because of speed. But if they made that boat with a 500hp single QSC Cummins, I would choose the single that has the same amount of power as the twins. I personally think choosing an extra engine for maneuverability is an awful lot to pay for that added maneuverability when thrusters are MUCH cheaper to maintain. And I think a single with a thruster is simpler to maneuver. Good luck....exciting times ahead.

PS...I do believe on those boats you enter the engine room thru the cockpit and there are no removable floorboards??? If that is the case, you need to make DAMN sure you can get around those twins.
 
Peter B said:
Taking into account what everyone else posting on here has said, realistically are you intending to do all the engine maintenance..? If not then the access is perhaps less of an issue, (mechanics tend to be younger and more supple)...
Click to expand...


I can add to this: the raw water pump on our port engine is on the outboard side, not easy for me to change that impeller.

I can do it, in a pinch... but the young engine tech in our yard can do it fairly easily, mostly by feel. I don't begrudge paying him to change that one as part of my routine service, even though I try to do most everything else myself. It's not a huge amount... and I don't hurt so much the next day.

-Chris
 
-high rev engines vs. slower turning ones. I thought all newish (maybe 2005 and newer) engines were higher revving and higher temp than the older models to meet pollution requirements. Is this not the case? Is it still possible to buy a new, clean lower rpm engine?
Click to expand...

Yes, I have a 2007 Cummins which I usually cruise from 900 to 1400 RPM. It is a common rail engine.

I would suggest you get the Best boat AFTER looking at engine accessibility, especially if you are going to do any of your maintenance.
 
Baker said:
And I think a single with a thruster is simpler to maneuver."
Click to expand...
I am now on my ninth boat since 1995 and all but one have been twin diesels. I am in complete agreement with the above statement as I had a single for 8 years and loved it! I could do a slalom course backwards with that boat. (Using the thruster to change direction.) My current boat is a twin which I bought for speed.
 

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maineman said:
Y-high rev engines vs. slower turning ones. I thought all newish (maybe 2005 and newer) engines were higher revving
Click to expand...

It may be that newer engines are higher revving than their prior counterparts, but the reference to high reving isn't 2,000 vs. 2500 rpm, its 2,000 ish vs high 3,000 ish. I just checked specs of a few Yanmar engines -- they are rated to 3,800 rpm.
 
Obviously a subjective question.
I think generally, you would find that folks with twins, have, from time to time said "Hey...right now, I wish I had a single.", and folks with singles may have said once or twice, "Hey...twins would be nice right now".
The frequency of those thoughts is going to vary by a large degree.

As you know, boats handle differently. To handle twins requires you learn how to handle/maneuver that configuration, and to handle a single (with/without thruster) will be considerably different.

When I bought my single MT34' Whistful, several boaters in the marina told me I should have purchased something with twins, because they are so much more maneuverable.
I was discussing this with friend who was a LONG-time trawler owner, while sitting on his sundeck with cocktails. He pointed to a lobster boat that was hauling traps in a very narrow cove. "Ever see a one of those small, coastal, lobster boats with twins?"...
Good point.
 
maineman;543701 And the concern regarding engine room access is very valid. I currently do all of my own routine maintenance. But anything that requires any real mechanical skill will have to be left to a professional. So said:
Think of what you do for your routine maintenance.
- engine oil and filters
- Secondary fuel filter
- air filters
- raw water impellers
- raw water strainers
- rust protection (spraying, painting etc...)
- check/adjust belt tension
- anode replacement

Then things that you may or may not do yourself
- Coolant flush
- aftercooler maintenance
- other mysterious stuff that I don't understand.

If I was looking to buy a boat with twins, I would seriously consider taking that list, and then crawling around the ER pretending I was doing those things. I spend more time than I wish doing engine maintenance and I just have a single and a genset. I am lazy but can't afford to hire out the relatively easy and routine stuff.
Click to expand...
 
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