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Old 01-13-2020, 07:26 PM   #1
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SP90 254 cu in. Ford Lehman

looking for any information on twin 90 Ďs on potentially new to me vessel. Not a lot of information comes up on these engines.

Does anyone have similar in there trawler?

Fuel mileage?

Duds? A trial engine that never was meant to be?

Or your personal thoughts on twin 90ís in a 36í - 26000 lbs Trawler?

Under powered?

My thoughts are cheap to run....?

Take care
Troy
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Old 01-13-2020, 07:30 PM   #2
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From what I know about them, they're basically 2/3 of a Lehman 135. So basically the same engine downsized to a 4 cylinder instead of 6.
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Old 01-13-2020, 07:47 PM   #3
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I believe there is a ton of the 135 going strong?

So in hind sight in stead of a single 6 cylinder pushing 30,000 lbs I could potentially have a 8 cylinder pushing 26000 lbs. lol

And maybe class it having a 4 cylinder wing engine when 1 goes down, there is another to get me back to port.

I like it!, redundancy!! Right?.?
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Old 01-13-2020, 07:55 PM   #4
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The experts/parts suppliers for these are American Diesel Corp,effectively the Lehman successors,owners previously associated with Lehman.
FLs came in 80 and 120, later the "Super"version came as 90 and 135 hp.
I have twin 120s in a 36ft, I think it would be ok with twin 90s, plenty came with a single 120. They were fitted to some IG32s, maybe GBs too.
Cheap on fuel, easy to service, parts available, no electronics, no turbo,simple agricultural type engines, certainly not a failed trial engine.
Some of the 80s used raw water as coolant, ie no heat exchanger system. I`d avoid them.
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Old 01-13-2020, 08:09 PM   #5
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Greetings,
Mr. O. You may be overpowered with twin 90's on a 36' boat.
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Old 01-13-2020, 09:58 PM   #6
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To much power is that a term? You don’t have to use it! No seriously are you being sarcastic?

I currently have twin 350 gassers that will burn everything including jelly fish and sea urchins! But will go fast.....

Really to much power??

It’s not what we are looking for, slow and steady wins the race, finish with a great glass of wine....and good company...
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Old 01-13-2020, 10:33 PM   #7
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Greetings,
Mr. O. Nope. Not being sarcastic at all. You were worried about being under powered with twin 90's. As mentioned, a goodly number of 36' boats have single 120's and that's plenty of power, eh?


We used to have a 34' Marine Trader that used about 2 GPH @ 7 knots. I think that was about 18HP to 20HP out of a 120 Lehman (my numbers may be off as I can't remember the exact conversion).
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Old 01-13-2020, 10:49 PM   #8
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Since the 90’s aren’t as smooth as the 6cyl. engine syncing the two could produce sone annoying harmonic vibration.
Does this boat have acceptable space on the sides of the engines for relatively painless servicing?

It sounds like you may not be a great candidate for trawler boating. The’re are a few somewhat trawler-like boats that actually are planing hulls. Such a boat may serve you well.
Looking at boats is fun. Have fun.
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Old 01-13-2020, 10:56 PM   #9
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Some boats, trawler(whatever that is) variety, may have more power than they can effectively use. There are boats in the 40-50ft range doing fine with twin FL120s. Over 6 litres capacity, unstressed, churning out torque and hp. At a certain point, extra speed compared to increased fuel use is minimal and unrewarding.
2x 90hp FLs in a 36ft "trawler" should be just fine. And more maneuverable than the often found single FL120. The SP series had a different injector pump saving the regular oil changes of the older series.
PS. I enjoyed visiting Kelowna, and the Okanagan Valley.
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Old 01-14-2020, 08:45 AM   #10
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Quote:
Originally Posted by RT Firefly View Post
Greetings,
Mr. O. Nope. Not being sarcastic at all. You were worried about being under powered with twin 90's. As mentioned, a goodly number of 36' boats have single 120's and that's plenty of power, eh?

LOL, I get it EH!


We used to have a 34' Marine Trader that used about 2 GPH @ 7 knots. I think that was about 18HP to 20HP out of a 120 Lehman (my numbers may be off as I can't remember the exact conversion).
I think the 90ís will be great!

So if you were getting 2 GPH out of FL120 @ 7 Knots. Being in the 3 GPH for the 90ís may not be that far off?
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Old 01-14-2020, 08:57 AM   #11
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Greetings,
Mr. O. I have no knowledge of the 90's so I can't even speculate as to their fuel usage. As well, there are so many variables (hull shape and condition, transmission gear ratio(s), prop size(s), engine condition and state of tune etc.) that even a guess may be way off.
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Old 01-14-2020, 08:57 AM   #12
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Since the 90ís arenít as smooth as the 6cyl. engine syncing the two could produce sone annoying harmonic vibration.
Does this boat have acceptable space on the sides of the engines for relatively painless servicing?

The annoying vibration is one our biggest fears, we do spend a lot of time at the lower helm. My worry was the engines being in the salon area. And if they were to small you would have them wound right up to keep cruising speed.

It sounds like you may not be a great candidate for trawler boating. Theíre are a few somewhat trawler-like boats that actually are planing hulls. Such a boat may serve you well.
Looking at boats is fun. Have fun.
No I think the Trawler is were we need to be, the lifestyle and era they bring is timeless.
I am just approaching this vessel purchase different than the one we have now. Even though it was beautiful when we bought it, I took it to another level and put a lot of time and money into it to make it near mint, and I still think itís beautiful.
But now we are doubting itís the forever boat for us, and or capable to do our longer journeyís comfortable.
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Old 01-14-2020, 08:58 AM   #13
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Yup,
It’d be like a 180hp single.
But i’d be a twin .... great.
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Old 01-14-2020, 09:10 AM   #14
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Some boats, trawler(whatever that is) variety, may have more power than they can effectively use. There are boats in the 40-50ft range doing fine with twin FL120s. Over 6 litres capacity, unstressed, churning out torque and hp. At a certain point, extra speed compared to increased fuel use is minimal and unrewarding.
2x 90hp FLs in a 36ft "trawler" should be just fine. And more maneuverable than the often found single FL120. The SP series had a different injector pump saving the regular oil changes of the older series.
PS. I enjoyed visiting Kelowna, and the Okanagan Valley.

The SP series gives you longer life between oil changes?

Yes the Okanagan is a beautiful place to vacation and live, but itís grown so much in the last 20 yrs and is very expensive. This is why we have started our pre retirement plant and headed to the coast with our boat.
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Old 01-14-2020, 09:21 AM   #15
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Greetings,
Mr. O. I think what Mr. BK is alluding to regarding "oil changes" is oil changes in the injector pump. The regular 90's and 120's have a stand alone oil reservoir that is the injector pump body, itself. Where engine oil changes are every 100 hours, injector oil changes are recommended, by some, to be every 50 hours.

The "super" series, as I understand it, have injector pumps that are lubed by the engine oil and are taken care of by regular engine oil changes.

I attended a lecture by the late Bob Smith (the ultimate guru of Lehman engines) and I remember him saying that one could change the injector oil at the same time as an engine oil change (every 100 hours). He said the manual recommendation of a 50 hour injector pump change was a misprint.

Edit: I think the 50 hour injector oil change was as a result of potential oil dilution by leaky internals in the pump itself as the pump aged. Our former Lehman showed evidence of this leakage. Upon draining there was a quite distinct odor of diesel. So I did do a 50 hour change on that pump.



Our current twin Lehman 120's have no evidence of diesel odor so I adhere to the 100 hour regime.


YMMV.
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Old 01-14-2020, 09:32 AM   #16
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What are your thoughts on running one engine?

Has anyone done this?

We have on our Carver for not a long time, but have tried it. Our cooling water enters from the sea cock / sea strainer / v drive / raw water pump / tranny cooler/ heat exchanger. So I was always worried the gears and tranny turning backwards would heat everything up. Any thoughts on this or how would FL plumbing be configured?

The interesting thing is fuel and speed on the carver. If I was doing 8 mph with all 16 cylinders turning, I would cut back to just 1 engine turning and drop to 6.5 mph. To get boat back to 8 mph increase the single engine 200 more rpm. The only thing I wish I had was fuel flow meters.

Could a person design a shaft brake? That might be problematic if you started the wrong engine I am thinking!..bad idea...

But a single 4 cylinder chugging down the chuck would be some good mileage, NO?
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Old 01-14-2020, 09:36 AM   #17
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How much you'll gain from shutting down an engine depends a lot on the boat. Depending on whether you can let your transmissions freewheel or not will impact drag (a locked prop is more drag than a freewheeling one). There's also some drag from having the rudders off-center while running on one.

Different engines will have different efficiency curves. A lot of diesels don't drop off too badly at light load, so shutting one down may save a little fuel, but not a lot. But a gas engine has horrible light load efficiency, so the gain from shutting one down and increasing load on the other is likely to be better.

Of course, there are also any electrical system concerns to be aware of as well as potential boat handling issues.

Now if you had a way to drive both props from one or both engines (like a diesel electric setup), you'd be onto something. Run 1 engine with full maneuverability, etc. until you need more power, then start up the second one.
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Old 01-14-2020, 09:37 AM   #18
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Greetings,
Mr. O. Lots of discussion and controversy about a twin running on one. Search the archives. MY opinion? Not worth the trouble. Fuel is a very small part of a boat budget.
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Old 01-14-2020, 10:02 AM   #19
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Ok yes I never thought of the free wheeling prop versus locked. I should have thought of that I follow a lot of sail boats that upgraded to feather props.

Hey maybe that’s a thought! They work on Cats with running one engine??
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Old 01-14-2020, 11:22 AM   #20
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With a displacement hull and many semi displacement hulls, there is pretty much a fixed horsepower required to get the boat to do hull speed. The amount of fuel required to produce that horsepower does not vary very much at all from engine to engine, especially the old clam-crushers most of us have. One engine producing 50 hp or two producing 25 or 30 each is approximately the same fuel burn.

Fuel is probably the cheapest component of boating. Moorage, insurance and repairs, haulout costs etc etc. I expect to pay out about 15 boat dollars this year and about one boat dollar for fuel. 6.5 or 7 litres/hour is immaterial. Also, A fuel flow gauge on a trawler is pointless, gilding the lily, so to speak.

Where your costs rise is in having 2 engines, double the maintenance and for that higher cost you get maneuverability (debatable) and redundancy, which for inshore use like most of our boating, is unnecessary.

RT, as usual, got it right.
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