Not Twins

I saw an add in YW for a 40' Defever Passagmaker with a Lehman 120HP - Starboard and a Perkins 135 HP - Port.* I'm slightly confused with the pairing.*

That sort of thing is not rare. When one of a boat's two FL120s craps out a viable decision made by a number of boat owners is to replace the failed engine only. But nobody makes the exact equivelant of an FL120 today so they get the closest thing.

A popular FL120 replacement in a single or twin is the engine marinized and sold by American Diesel. Based on a new Ford of England 6-cylinder diesel, it is a drop-in replacement for the FL120. Uses the same mounts, bolts up to the same transmission, and so forth. It's a 150 hp engine instead of a 120 hp but apparently it pairs up with the FL120 very nicely. There are a few people on the GB owners forum who have this setup. I don't know if this engine is still available--- I recall reading recently that the base engine has been discontinued by Ford, but I'm not positive on this.

Another popular FL120 replacement is a Lugger 6-cylinder, NA diesel. It, too, is 150 hp or so but apparently pairs up nicely with an FL120 in a twin. However it is not a drop-in replacement so new engine mounts need to be fabricated to support the engine and position it for a transmission.

How would you sync the two engines?

I don't know how they do it for sure. I suspect they get the engines synced up so they are running at the same speed and aren't pulsing harmonically and then figure out the correct pitch for each prop so you're getting equal thrust from each prop. There's probably a bunch of math involved which is why I don't know how they do it

The engine "out of sync" beat is what drives you nuts, not the props being somewhat out of sync. The props on our boat don't turn the same rpm when the engines are running at the same rpm due to the difference in gear ratios between the counter-rotating BW Velvet Drives. Don't hear or feel*the props being out of sync but get the engines out of sync just a tiny bit and you sure hear that.



-- Edited by Marin on Tuesday 1st of February 2011 01:14:52 AM

KJ
I would pass on a Mickey Mouse setup like that. There are to many good deals on nice boats today to fool around with mix and match engines. Think of the nightmare of carrying two sets of spare parts for different engines by different manufacturers.

True enough, and I would not want to buy a boat that was already set up like that. But the people I've heard of who have isntalled a different engine in place of a failed engine in a twin have done so because they didn't want to get rid of their boat but replacing both engines was economically unfeasible. So replacing just the one solved their dilemma. I wouldn't want this setup myself because it does seem a bit Mickey Mouse to me, too. But the people on the GB forum who've done this are very, very happy with the results and cite no operational problems as a result of running two different engines. They certainly don't claim it's as ideal as having two of the same engines, but it was a way for them to keep using and enjoying their boat without forking over the money for a complete re-power.

I've "heard" of people who hired a hooker to kick them in the nuts with a high-heeled shoe.* That doesn't make it right.*

Egregious wrote:

I've "heard" of people who hired a hooker to kick them in the nuts with a high-heeled shoe.* That doesn't make it right.*

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I didn't realize you knew what was "right" better than the people who have elected to replace a failed engine in*their twin with a different engine.* I suggest you contact all these people and tell them that all their reasons for keeping their boat going are wrong and they should immediately*decommission their boat until such time as they can afford to replace both engines.

-- Edited by Marin on Wednesday 9th of February 2011 12:22:38 AM

Marin wrote:


Egregious wrote:

I've "heard" of people who hired a hooker to kick them in the nuts with a high-heeled shoe.* That doesn't make it right.*

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I didn't realize you knew what was "right" better than the people who have elected to replace a failed engine in*their twin with a different engine.* I suggest you contact all these people and tell them that all their reasons for keeping their boat going are wrong and they should immediately*decommission their boat until such time as they can afford to replace both engines.

-- Edited by Marin on Wednesday 9th of February 2011 12:22:38 AM
In a pinch you gotta do what works, even if it isn't "right."*** I'm just giving you a hard time for posting hearsay.*

*

Egregious wrote:In a pinch you gotta do what works, even if it isn't "right."*** I'm just giving you a hard time for posting hearsay.*

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I will let the members of the GB owners board who have installed a different engine in their twin to replace a failed FL120 and who have posted about it on that forum*that you believe they are lying.

Followiing your dumba*s philosphy, everything anyone learns in school from kindergarten through elmentary, middle, and high school and then college and advanced degrees like law and stuff is "hearsay" since we just have to take the teachers' word that what they are telling us is correct.* That and the stuff we read in the textbooks, which, since we didn't experience any of it directly ourselves, must be hearsay, too.* Those authors aren't to be trusted, you know.

What an idiotic attitude.

*

I would'nt claim it to be perfect but there's not much wrong w it. One would need to prop the weakest (lowest hp) engine for WOT to be at rated rpm like any other proper setup and put the same prop w the same pitch as the low hp engine on the "new" engine. I'm assuming the "new" engine has a WOT rated rpm at least as high as the original or it would then be "Micky mouse". Since the new engine would be slightly under propped one would need to be a bit careful not to over rev same. Not perfect but none the less a reasonable solution to a problem and the resulting boat is probably worth what it would be worth w only one engine plus what it cost to purchase and install the odd engine. The only probable difference under way would be that the odd, new or 2nd engine would be a bit underloaded and many or most here under load more. I agree w Marin* ..a dam fine idea.

nomadwilly wrote:

I would'nt claim it to be perfect but there's not much wrong w it.*.... I agree w Marin* ..a dam fine idea.

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Eric---* I'm sure you realize this, but just to be clear, nobody that I'm aware of who's done this claims it's an ideal way to power a boat.* The people on the GB forum who've repowered one side in this way certainly don't.* But the choice for them was not to be able to use their boat because of the failed engine or replace the failed engine with a new, zero-time engine and continue to use and enjoy their boat.* The cost of replacing both engines*exceeded their boating budgets.* And they didn't want to get rid of their boat for another one for whatever personal reasons.* So the repower on one side made sense to them.

From what these GB owners posted to the forum, rebuilding the failed FL120 was not a viable option in their opinions.

Some of the GB folks used the American Diesel engine, which is a physical drop-in for the FL120.* It's 150 hp vs 120 hp, but no modifications are needed to the boat to install it.

-- Edited by Marin on Wednesday 9th of February 2011 07:22:59 PM

"But the choice for them was not to be able to use their boat because of the failed engine"

Thats one of my best arguments AGAINST owning a twin screw vs single screw.
With twin screw, you DOUBLE your probability of having a mechanical problem and as a result you will NOT leave the dock until its resolved.

Twin engine is not one primary and one spare. Its TWO primary engines.

R.

I agree with Ralph on this. One engine. Anything baby needs, baby gets. *

IF there is ever a serious problem...
Out with the old, in with the new.
New power = New boat.

Twins are better in most ways and they are more expensive as are most better things.
If it's as similar as the engines we've been talking about you could put a different brand of tire on one side of your car and not notice the difference either. Or you could wear different shoes on each foot. The argument about twins v/s singles can be settled right here and now. There's lots of twins out there and people paid more money for them. People only pay more money for something if they think it's better. But about the different brand twins** ..it would be nice if we had someone on here that had experience with such a system and is willing to share. But w the Lehman and Perkins marriage they are so much alike I don't see any problem that a group of good mechanics or engineers could object to loud enough to put the combination in a "don't do it" category. BUT** ...the boat would be worth considerably less so the boat broker may have the best advice on this mechanical issue. You may be a culinary nut and want a really large kitchen so you want to make the living room into kitchen as well but your real estate agent will say "don't do it".

"People only pay more money for something if they think it's better."
This is certainly true about twin engines in trawlers.

They have been sold a line of crap from salespeople.

Twin engines in a displacement hull boat offers very little benefit to performance. The $$$/Benefit ratio is way too high. You definitely have a benefit in docking with twins....but what benefit do you have when anchoring?

If anything, with twins you are generating TWICE as much heat in the engine room on those hot summer days. Now when you lie at anchor at night the heat is still rising from that really hot engine room.

Then we have "trawler" companies who try to make "fast trawlers" by jamming into them as many horse power as they can, flatten the bottom and let the owner suck up 40galls/hour to go 20 kts (a notional example). All of it is sales gimmickry. Then the new owners can tell everyone they can "outrun storms"....Yeah Right.

The comment earlier hear about hookers and high heels was correct ....just because someone does it doesnt make it RIGHT.

The originator of this thread mentioned a twin engine 40 footer. I can tell you that is one tight engine room. If the owner is fat, he might not even be able to do some of his own maintenance on one side of one engine.

For a slow moving boat like a trawler, single engine is the only thing that really makes sense. For a retiree, single engine is half the engine maint. cost of twins.
And the boat moves through the water at essentially the same speed....ok maybe 1 or 2 kts different at most.

R.

nomadwilly wrote:

But about the different brand twins** ..it would be nice if we had someone on here that had experience with such a system and is willing to share.

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Eric--- I will pose your question to the GB owners group and see if anyone responds.* I've always been curious how they "balance" the 150 hp engine with the 120 hp engine.* If there is any meaningful reply I will post it here.

*

ralphyost wrote:

The comment earlier hear about hookers and high heels was correct ....just because someone does it doesnt make it RIGHT.

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The single vs twins in a totally unwinnable argument except in the mind of each person defending whatever their choice is.* The statement that a single is "right" is as ignorant as the statement that twins are "right."

Rehashing all the reasons for one over the other is a pointless exercise in this dicussion since it's all been covered before, not only in this forum countless times but in virtually every other forum including the GB owners forum.

Both singles and twins offer advantages not shared by the other.* They also offer disadvantages not shared by the other.* Every boater's reasons for getting what they got are valid for that boater.* To say or imply that a boater made a "wrong" decision because they bought a twin-engine boat is a dumb as saying a boater made a "wrong" decision by buying a single.

I've run both and when we decided to buy a larger cruiser we did not really care whether we got a single or a twin.* Having had a twin for some twelve years now, I can say that neither I nor my wife would ever want a single engine cruiser of the same type.* If we decided to switch to a different kind of boat, like Carey's lobsterboat, that would be a different matter because by definition they are single-engine boats.

So for us and what we want from our boating experience, a twin fits the bill, a single would not.* But that has absolutely no relevance whatsoever for the fellow five slips down who has a single-engine cruiser.* For him, that's what meets his requirements for his boating experience.

I think it's totally valid to discuss the advantages or disadvantages of singles and twins as the information can be useful to someone trying to decide what would be best for them.* But to say or imply that one is inherently better than the other is not only wrong, it can be misleading to someone getting into boating.

Would the size (displacement?)*dictate at which point a single engine*would no longer be practical,*or could you always find an engine powerful enough to drive any size boat?* If I were planning on doing multiple crossings say from Fla to Bahamas, would that dictate twins over a single?***** KJ

KJ wrote:
Would the size (displacement?)*dictate at which point a single engine*would no longer be practical

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Most oil tankers, bulk carriers, container ships, etc. are single engine.

Here is the diesel engine in the single-engine container ship, Emma Maersk, I believe still the largest container ship in the world.* Note the fellow up on the top gallery of the engine preparing to start it with the optional pull-cord.






-- Edited by Marin on Thursday 10th of February 2011 03:29:30 PM

Yeah,*I saw that on the Discovery channel.* Pretty amazing.
What*would you*want for a 40' - 45' trawler crossing the Gulf Stream, would you prefer a single or a twin? I know there are other factors to consider but overall what is your opinion?
*(I knew I was going to get drawn into this sooner or later).* All the boats that I have looked at so far have twins.*** KJ*

Cruise ships typically have multiple primary*diesel engines, five isn't uncommon, and two electric-powered propellers (excluding* thrusters).* The number of engines used depends on the electrical load.* Cruise ships don't operate at a constant speed.* Speed is dependent upon the ship's schedule.* For instance, they hardly move for hours*during overnight trips between Victoria and Vancouver.

I pretty much limited my search to keel-protected, single engine/propeller trawlers.* Since I will be boating mostly*in shallow waters, I avoided boats with unprotected propellers and shafts.

It's a toss up. With twins you need to keep then synced or the harmonic slightly out of sync drumming will drive one nuts but when one engine overheats or otherwise gives trouble or even quits you'll be kinda glad you've got the other. But it's actually possible you'll need the shallower draft of the twin but you'd need to be more careful unless your twins were as well protected as a single. Of course the single was cheaper to buy so maybe you've got more money to spend in the Bahamas when you get there. When you go to the yacht club you'll be looked up to since you can afford a twin but on the hook w the trawlers you'll be more respected because you've got the guts and perhaps manliness to go forth w only one engine. It's a wash for most but for me I go many places that the loss of my single engine would be big trouble so for me it's a no-brain-er**** ...I'd have twins if I could afford it. And w an airplane I'd have 3 or 4 if I could afford it.

Could you hire an expert marine diesel mechanic to sync your twins (if you had them)? *

nomadwilly wrote:It's a wash for most but for me I go many places that the loss of my single engine would be big trouble so for me it's a no-brain-er**** ...I'd have twins if I could afford it. And w an airplane I'd have 3 or 4 if I could afford it.

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It is hard to believe that shipping companies risk millions of $$$ having only one engine in their freighters.* So, maybe it isn't a bad choice for us.

*

KJ wrote:

Could you hire an expert marine diesel mechanic to sync your twins (if you had them)? *

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Syncing twins is done with the throttles and your ears (and your feet because you can feel it, too).* You simply nudge one throttle or the other until the thrumming is gone.* Some engines can have syncronizers installed on them which sync the engines automatically.* The out-of-sync conditon being talked about here is the matching of the vibrations--- harmonic and otherwise--- of the two engine so that you don't get them pulsing against each other.*This "sweet" spot occurs when both engines are running at exactly the same rpm.* Being out of sync a bit makes no difference to the engines, but as Eric says, the sound will drive you nuts.

The engines on a multi-engine airplane need to be synced, too, be they piston or turbojet engines.* You can do it by hand just like*with a boat but most planes have auto-syncronizers.* Our boat does not have engine syncronizers so we do it by hand.* It's so easy even a caveman could do it.



-- Edited by Marin on Thursday 10th of February 2011 06:38:37 PM

And then there are all those crazy risk-takers flying single-engined airplanes over the Alaskan wilderness.

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markpierce wrote:

It is hard to believe that shipping companies risk millions of $$$ having only one engine in their freighters.* So, maybe it isn't a bad choice for us.

*

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RickB can give you a*more meaningful response but there is little similarity between the maintenance and skilled labor available to keep the engine on a container ship, tanker, etc. running correctly and the world the engine in a recreational boat lives in.* As I understand it, the engine on many ships can be worked on (to a degree) while the engine is running.* Cylinders can be taken off-line and repaired or adjusted or whatever.* So "single engine"in the commerical world is a whole lot different then "single engine" in the toy boat world we live in

*


-- Edited by Marin on Thursday 10th of February 2011 06:39:30 PM

Marin wrote:

Syncing twins is done with the throttles and your rears (and your feet because you can feel it, too).* You simply nudge one throttle or the other until the thrumming is gone.*...

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Seems to me this makes operating twins more interesting, helping to stay the boredom caused by knowing one can afford one engine to fail.

*


-- Edited by markpierce on Thursday 10th of February 2011 06:42:00 PM