Best way to quiet my Lehman 120 Exhaust

Shower head it a name for the place where the water enters the exhaust to mix and cool it. It ually has a lot of smallish openings circled all around the outside diameter . They are supposed to spray water all around so there are no local hotspots before everything gets mixed up flowing through the pipes.

What you see on the outside is one water pipe entering the exhaust but inside there is usually an inner and outer tube inner for exhaust outer for water. The water mixes with exhaust at the end through the small holes or some other structure to assure full diameter converge. Some are slots some are holes but only the smallest engines just dump water into the exhaust directly.
if you google <marine diesel exhaust elbow> you will find links to some PIX of various designs.

Again look for simple stuff before getting too concerned about the fancy stuff.

Chris used vinegar, baking soda and hydrogen peroxide to bring our cap rails back from black.

Two ways to quiet down an old Lehman.
Lift mufflers or repower w a gas engine.

bayview said:

Shower head it a name for the place where the water enters the exhaust to mix and cool it. It ually has a lot of smallish openings circled all around the outside diameter . They are supposed to spray water all around so there are no local hotspots before everything gets mixed up flowing through the pipes.

What you see on the outside is one water pipe entering the exhaust but inside there is usually an inner and outer tube inner for exhaust outer for water. The water mixes with exhaust at the end through the small holes or some other structure to assure full diameter converge. Some are slots some are holes but only the smallest engines just dump water into the exhaust directly.
if you google <marine diesel exhaust elbow> you will find links to some PIX of various designs.

Again look for simple stuff before getting too concerned about the fancy stuff.

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I think the name you are thinking of is " spray ring "

Heads have shower heads.. exhausts have spray rings..
HOLLYWOOD

hollywood8118 said:

I think the name you are thinking of is " spray ring "

Heads have shower heads.. exhausts have spray rings..
HOLLYWOOD

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Bingo!

So that is why I smell like diesel after a shower, thanx for clearing that up.

Here's the transom mount muffler I was talking about:

http://books.google.com/books?id=A34FLGA

Salisbury Hydro-Vac

OP has tried two different types of water lift muffler with no change. Water lifts are usually VERY effective at killing exhaust note, so I really wonder if drone is from another source.

Capt.Bill11 said:

Here's the transom mount muffler I was talking about:

http://books.google.com/books?id=A34FLGA

Salisbury Hydro-Vac

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Link seem to be broken...

Capt.Bill11 said:

Here's the transom mount muffler I was talking about:

http://books.google.com/books?id=A34FLGA

Salisbury Hydro-Vac

Click to expand...

I Googled it and found it, I was actually thinking about those. I remember seeing them on old wooden Chris Crafts when I was a kid. Wonder why they stopped making them and or using that design.....

hollywood8118 said:

I think the name you are thinking of is " spray ring "

Heads have shower heads.. exhausts have spray rings..
HOLLYWOOD

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So can these spray rings get clogged up as suggested? I assume removing and/or replacing the exhaust manifold elbow is the only way to get at them...

Yes and yes.

A common cause of a "droning" sound at the exhaust is your engines being out of synchronization. Have you listened to the exhaust sound of one engine under load with the other shutdown?

Lehman 120 exhaust elbows don't have spray rings. The raw water is pumped into a slot at the top of the elbow where it falls down into the exhaust flow. The elbow is cast steel.

Lehman/Sabre 135 exhaust elbows are stainless and do have spray rings, but they aren't interchangeable.

Probably the best way to increase water flow in a 120 is to change the Jabsco 3/4" pump for a Johnson 1" pump. Marin has posted on this previously and it is significant, since the Jabsco pump drive is a know weakness of these motors.

av8r said:

.... since the Jabsco pump drive is a know weakness of these motors.

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Just one tiny clarification. The pump drive coupler on the FL120 is not a Jabsco item. The raw water pump it drives is. But the drive coupler itself was designed by Lehman and manufactured for them as part of their marinzation kit for the Ford Dorset diesel (FL120). I was told by the person who designed the drive coupler that it was very difficult to manufacture, and this plus the design itself made for a weak drive tang, the part of the shaft that mates to the slot in the Jabsco pump.

Marin said:

this plus the design itself made for a weak drive tang, the part of the shaft that mates to the slot in the Jabsco pump.

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AV8R: Interesting thought.

MARIN: Are you suggesting that the tang can't handle the 1" Johnson pump?

If I can get more water flow I'd certainly consider upgrading pumps as an option if it's a significant increase.

Rduval said:

AV8R: Interesting thought.

MARIN: Are you suggesting that the tang can't handle the 1" Johnson pump?

If I can get more water flow I'd certainly consider upgrading pumps as an option if it's a significant increase.

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I don't know if I'd be in a big hurry to change your pump out. There are plenty of Lehman's out there with their original raw water pumps and they're still going strong. Plus Lehman's are not prone to over heating even when the raw water flow is reduced do to say an impeller losing blades.

It's a nice up grade. But hardly mandatory.

Rduval said:

So can these spray rings get clogged up as suggested? I assume removing and/or replacing the exhaust manifold elbow is the only way to get at them...

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most of the time they rot out before clogging
HOLLYWOOD

If your concerned about water flow make sure all the restrictions in the system, from the screen outside the thru hull ( classic restriction due to successive bottom paint coats ) to short bends in the hoses and hard fittings, crap in the first exchanger down stream from the raw water pump (impeller bits) narrowing of the opening of the casting where the seawater is injected into the exhaust elbow due to corrosion. If you can hold hand on the exhaust AFTER water injection, and the ray water pump is cool when the engine is operating you should be getting enough water flow.

Also, the " droning sound" on Volunteer went up significantly when I removed insulation the P.O. had wrapped around the waterlift muffler due to it starting to degrade and fall apart.. replacing the insulation reduced the resonance caused by the exhaust pulses.


HOLLYWOOD

Disclaimer.. watch the hot and rotating stuff .. both have been known to be magically attracted to flesh.

Rduval said:

Hi All:

So I have a pair of 120 Ford Lehmans which currently have a very "droning" exhaust note. Wondering what (if anything) others have done to quiet the exhaust note.

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Sounds like typical old twin engine drone to me. Try running with one engine shut down and then the other to see if any difference. Next, insure both engines are operating at same exact RPM. Twins drone badly if RPMs not identical - especially old ones where internal metal parts are flapping around. Need I say Aetna and strobe light?

Marin, any stories about trying to sync a Ford Tri motor?

Someone mentioned in an earlier post about using vinegar to flush the cooling system.
Clear vinegar is a cheap and effective method of cleaning the cooling system and will dissolve any calcium deposits in the cooling system.
Best is to buy a minimum of 8% strength if available, fill the system as described earlier, let it stand for 4 hours, then flush out and repeat the process 2 or 3 times before reconnecting normal hoses.
The reason for the repeat flushing are that the vinegars strength will be diluted back to a neutral ph. as it dissolves the calcium, in layman's terms the vinegar and lime will turn to water if the quantities are equal.
After this process I would recommend reverse flushing the whole cooling system with a dockside water hose, that will leave the system nice and clean for trouble free cruising.
In respect of the 'droning' noise I would fit air filters on the air intake first as the cheapest option as it will cut the engine noise by up to 30% anyway.
If you have a smart phone there is an app called Decibel, you can use it to measure sources of noise to track down the culprit.

Sure they can get clogged or rusted.
Look I'm not trying to give people more to keep them awake at night but they do exist.
Low flow usually comes from something before these

Rduval said:

MARIN: Are you suggesting that the tang can't handle the 1" Johnson pump?.

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The tang is not a factor with the Johnson pump conversion.

When an FL120 is converted to the one-piece Johnson pump, the Johnson pump replaces BOTH the drive coupler AND the Jabsco pump. So the entire, two-part origional system goes away. The Johnson pump mates to the same gear in the engine's accessory case that the Lehman drive coupler mated to.

With regards to the longevity of the drive tang on the Lehman drive coupler, there is no telling how long one will last before it cracks and breaks.

Our engines had about 2500 hours on them when a leaking raw water pump on the port engine prompted pulling the pump to rebuild it. I had replaced the impeller and the seals but the pump still leaked so it obvously had a more complex problem. When the shop removed the Jabsco pump, they saw that the drive tang on the Lehman drive coupler had cracked almost all the way through and was starting to deform. It was very close to breaking altogether with about 2500 hours on the clock.

This is what prompted us to switch to the Johnson pump. Since we were doing one engine, we figured we might as well do both of them. When the shop removed the starboard pump and drive coupler, they found that the tang on that drive coupler was just fine. So we kept that coupler and its Jabsco pump as a spare raw water pump system should we ever need it.

Which goes to show that the longevity of the drive tang on a Lehman drive coupler is anyone's guess. They may go for many thousands of hours with no problems at all, or they may crack and break in a couple thousand hours.

As I mentioned, Bob Smith at American Diesel designed the coupler when he worked for Lehman, and he told me that it was very difficult to manufacture. He also told me that the drive coupler was the only component of the FL120s marinizatoin kit to have ever had a factory recall. He told me the design made sense at the time, but in looking back on it he would have come up with a different design.

He said the attempted fix to a cracked or broken tang is to weld it back together. According to him, this fix is short-lived at best.

Converting to the Johnson pump elimates the potenttial problem altogether, and is one of the four best mods Bob feels can be done to an FL120.

The Johnson pump recommended for the FL120 is the 3/4" pump, The pump recommended for the FL135 is the 1" pump. However, the 1" pump will fit on the FL120, and it gives an increased water flow over the 3/4" pump. This makes no difference to the engine temperature, which is controlled by the thermostat. But it does make a significant difference to the transmissions, which on our boat run noticeably cooler than they did with the original setup. And anything that helps a transmission run cooler is a good thing to my way of thinking.

Photo is the 1" Johnson pump on our port engine.

Is that incoming 90 deg. nipple and hose on the pump 3/4" or 1"? Is your strainer 3/4" or 1"?

I talked to a mechanic in Campbell River who worked on and owned FL120's.
He said when the tang breaks the piece goes down the gear case.
The gears are destroyed, the needs to be pulled and all the gears replaced.
In essence, rebuild the engine.
Try to "fix" the problem before it happens!!!
Ted

Ted said:

I talked to a mechanic in Campbell River who worked on and owned FL120's.
He said when the tang breaks the piece goes down the gear case.
The gears are destroyed, the needs to be pulled and all the gears replaced.
In essence, rebuild the engine.
Try to "fix" the problem before it happens!!!
Ted

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If he says so. But in 30+ years of dealing with Lehman's I've never seen nor heard of that happening.

In fact I'm not even sure it's possible for the tang to get to the gears. I think it would be trapped in the housing. But I'd have to take a look at one to confirm my memory on that.

But look at this picture and tell me how a broken tang would get into the gears? It would have to get passed the shaft, passed the bearing/s and then passed the back of the gear itself which is as I recall pretty tight up against the housing to get to any gear.

Capt.Bill11 said:

If he says so. But in 30+ years of dealing with Lehman's I've never seen nor heard of that happening.

In fact I'm not even sure it's possible for the tang to get to the gears. I think it would be trapped in the housing. But I'd have to take a look at one to confirm my memory on that.

But look at this picture and tell me how a broken tang would get into the gears? It would have to get passed the shaft, passed the bearing/s and then passed the back of the gear itself which is as I recall pretty tight up against the housing to get to any gear.

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I had not seen one of these opened up.
My Mistake!
Checked , the problem was the adapter housing is the bearing.
The shaft wears it, becomes "sloppy" and wobbles, works the key out of the gear.
I apologize
Ted

Marin said:

the 1" pump will fit on the FL120, and it gives an increased water flow over the 3/4" pump. This makes no difference to the engine temperature, which is controlled by the thermostat. But it does make a significant difference to the transmissions, which on our boat run noticeably cooler than they did with the original setup. And anything that helps a transmission run cooler is a good thing to my way of thinking.

Photo is the 1" Johnson pump on our port engine.

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Thanks for the info Marin. DId you upsize any of the hoses or upsize the coolers themselves to 1" or only the pumps?

Ted said:

I had not seen one of these opened up.
My Mistake!
Checked , the problem was the adapter housing is the bearing.
The shaft wears it, becomes "sloppy" and wobbles, works the key out of the gear.
I apologize
Ted

Click to expand...

Hey no apology necessary. You just had me scratching a hole in my head trying to figure out just how that would be possible.

Rduval said:

Thanks for the info Marin. DId you upsize any of the hoses or upsize the coolers themselves to 1" or only the pumps?

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The oversize sea strainers we had installed when we got the boat are one or one and a quarter inch output, I don't remember. There were step-down adaptors used to feed the original Jabsco pumps. When the Johnson pumps were installed the hoses from the strainers to the pumps were changed to one inch. The oil cooler was not changed but the coolers we use can accept both 3/4" and 1" hose, so the pump to oil cooler was changed as well. Downstream of the oil cooler everything stayed the same.

When we had the Johnson pumps installed the waterflow out the exhausts became noticeably greater, even at idle, and the running temperature of the transmissions became noticeably cooler. By feel-- I have never taken any actual temperature readings. But where before they ran at a temperature where I could keep my hand on them but just barely, they now run at a temperature that I can keep my hand on quite comfortably.

The pumps we had installed on our engines are a bit larger than the pump typically used on the FL120. The pumps fit just fine but there is very little clearance between the pump and the injection pump sump drain fitting. I devised a split tube arrangement for catching and conducting the flow of oil out from under the injection pump, but there is very little working space. Bob Smith told me I could rotate the pump to move the outflow fitting in next to the block to gain a bit more working space at the injection pump drain but the split tube thing I came up with works fine so I haven't done this.

I did add the GGB inserts on our SP225 Lehmans. The exhaust is still fairly loud but it is now a more mellow sound, not as strident as it used to be. To us, it was well worth the money. I think I bought the longest ones they made.

Bob