Do new engine mounts equal less noise and vibration?

[ralphyost]

Forklift -

Here are some pics of my OLD motor mounts taken in 2008.

[url]http://tinyurl.com/3sjlrm2[/url]

I could not tell by inspection that the old motor mounts had anything wrong with them. I just decided that since I didnt know anything about the history of them being changed, I was going to do it this year. Then when I had to get a new engine, that was the logical time to do it (when the old one was pulled out).

The new engine runs very nice. Everytyhing is very smooth. But at 1800 I can feel vibration when I am steering from the main cabin. Up on the fly bridge I dont feel it much at all at 1800 RPM. At 1700 RPM, its dead smooth. Normal cruise for Lehman 120 is 1800.

Ran the boat yesterday from Greenwich NJ on the Cohansey River up the Delaware River, through the C&D Canal, then down the Chesapeake Bay. Normally we run as long as we can and stay overnight somewhere on the hook - Still Pond, Fairlee Creek, etc.

But we had the tide PERFECTLY timed yesterday. Left the boat yard at 6:45pm and made it all the way to our home dock at Rock Hall MD at 4:30pm. Thats about 80-85 miles - averages 8 kts for the day.

Changed the oil after we got in. Next weekend I will adjust the valves and retorque the head bolts.

R.


-- Edited by ralphyost on Sunday 1st of May 2011 06:26:24 PM

 

[Forkliftt]

Thanks for the update Ralph. I have a different style mount on my 135's, but after your experience I may swap out a set at the time and assess the improvement. Well done on your trip home! Sounds like everything was going your way!

 

[Mappy]

RE: Do new engine mounts equal less noise and vibration? _ CORRECT PROPS?

Eric wrote:

Mappy, The 4-236 Perkins is rated;

82hp at 2800rpm

194 ft lbs at 1460rpm

So at wide open throttle (WOT) you should run 2800rpm.

500rpm over propped is way overpropped.

Probably need 2" less pitch.

Hi Eric

I checked with Flywright who is running the same engines/boat he gets max RPM of 2800 and uses 2100 - 2300 for cruise. His survey says his props are 20 x 18.

My boat has 20 x 16 props, max throttle position give me 2350 rpm. The engines rev to 2350 very quickly. Is it possible that the throttle controls are not going to full fuel flow? Or could my tacks be out by 20%.

It does not make sense to me? Do I need 2" more pitch?

Roger



*

 

[ralphyost]

Fortklift -

Last fall when I bought these new engine mounts,I called American Diesel to order them. Bob Smith and I discussed it. They sell two basic types, with one being more expensive than the other. Bob counseled me that he couldnt exactly say there was a definite benefit to the more expensive ones and convinced me to order the regulars.

R.

 

[BaltimoreLurker]

BaltimoreLurker wrote:
I get a pretty rough idle below ...* oh ... 800-900 RPM, or around there.* What's the trick to drop the idle RPM and keep it relatively smooth?

*Any thoughts?* Anyone?

 

[FF]

... "800-900 RPM, or around there. What's the trick to drop the idle RPM and keep it relatively smooth?"

First "trick" is to borrow a hand tach and calibrate your setup.

If you drive the tach with a cable or its own pulse generator it may not be very far off. 10-15%

BUT if the signal comes from a simple alternator pick up , a calibration is in order, as first step.

 

[Nomad Willy]

Mappy,

Maybe your governors are limiting the top rpm. I'm very suspicious about the "The engines rev to 2350 very quickly." Does the last 5 to 10% of rpm gain as quickly as at 3-500rpm less? I recommend you (or your mechanic) check the governor. As a preliminary put your boat in neutral and go carefully to WOT. Your engine should come up to about 3000rpm. If it does not get it adjusted and check your throttle linkage for full throttle travel. And does Flywright have the same gear ratio? My engine does the last 200rpm slowly and the last 100 to 50rpm very slowly. I'll bet your governor is at fault AND if your gear ratios are the same as your friend you will probably need the 2" pitch increase.

 

[Mappy]

Thanks Eric

I shall investigate and report back. I am in the midst of an instrument upgrade and re-org for the lower helm so I won't get to the govenors etc for awhile.

Roger

*

 

[Baker]

FlyWright wrote:
Roger, what RPM are you running at? I have the same boat/engines and have for the most part run at 2350 RPM for 8 Kts. That's what the PO did and I have followed his advice.

Two weeks ago, I spent a week on the boat and had the time to try other power settings. I found that 2100 RPM cost me about 1 kt with MUCH improved sound levels and vibrations. Conversations were much less strained in the salon during cruise. I probably have aging mounts, too, but found this reduced power to be a great improvement.

Keep us posted on your findings and decisions.

*That is only a 2600RPM engine. *Running them at 2350 is running the P*** out of them. *Like the OP said, that engine is happy around 1800RPM can certainly run well at 2000....but once you get over 2200 I think you are running some life out of them....Just my opinion as having owned a 4236 for 6 years.

 

[FlyWright]

Baker wrote:FlyWright wrote:
Roger, what RPM are you running at? I have the same boat/engines and have for the most part run at 2350 RPM for 8 Kts. That's what the PO did and I have followed his advice.

Two weeks ago, I spent a week on the boat and had the time to try other power settings. I found that 2100 RPM cost me about 1 kt with MUCH improved sound levels and vibrations. Conversations were much less strained in the salon during cruise. I probably have aging mounts, too, but found this reduced power to be a great improvement.

Keep us posted on your findings and decisions.

*That is only a 2600RPM engine. *Running them at 2350 is running the P*** out of them. *Like the OP said, that engine is happy around 1800RPM can certainly run well at 2000....but once you get over 2200 I think you are running some life out of them....Just my opinion as having owned a 4236 for 6 years.

Baker, thanks for the advice.* I agree that it's working them harder than necessary, but I figured it was about 84% of 2800 RPM, not 90% of 2600 RPM.**Both engine*RPMs match at 2800 RPM WOT.* All I've read says 2800 is WOT on this boat.* At 2350, my average hourly fuel burn over about 300*hours of operation is 3.75 GPH (1.875 GPH per side).*

Here's a link to a similar (brief) discussion:* http://www.marineengine.com/boat-forum/showthread.php?387718-Perkins-4.236-Maximum-rated-RPM-for-marine-application

I am rethinking*my past practices*and will probably settle in at around 2000-2100 RPM as a new cruise RPM target.* My calculations show 2100 RPM is 75% which seems more in line with what I SHOULD be running.* I expect to get about 7 Kts at that power setting.

 

[Nomad Willy]

The percentage you should be looking for is percentage of load** ...not rpm. They are way different. Most experts agree a marine engine should be operated at 65 to 75% of max load and that is higher than 60 to 75% of rated rpm. Compare your cruise fuel burn rate w what the manufacturer specs for WOT burn rate and that will give you the load at 2350. If you burned 2gph at X rpm and the manufacturer says WOT burn is 4gph you would be at 50% load at X rpm. I say 2350 should be fine unless there is something wrong w your engine.

 

[FF]

"They are way different. Most experts agree a marine engine should be operated at 65 to 75% of max load"

It depends on the "marine " engine source.

An industrial engine will be delighted with 80% rated load @90% rated RPM , basically "forever".

A car transplant will be far lower , and may not even HAVE a 24/7 rating.

Light truck and farm tractor engine marinizations are selected for their construction that allows long periods with minor loading , but 50% of its rating is a good operating area.

Fuel burn , not RPM is a good measure of loading.

And keeping in mind what service the engine was built for is a good idea.

One reason "fast trawler" is an oxymoron.

 

[Nomad Willy]

Fred,

Truck, industrial and tractor engines? I'm talk'in about those engines w water cooled exhaust manifolds. Thanks for reiterating the percentage of max fuel burn is the load**** ...."Fuel burn , not RPM is a good measure of loading." I thought I'd seen the light when I learned that. I've run my 3000rpm engine at 2500 for hours on several occasions and 2700 should be fine. I think I'd look at the book before running at 2800 though. For 75% load a Ford Lehman would need to burn 4.5gph. And I can't imagine a marine engine not capable of a continious 75% load.

 

[FlyWright]

Does anyone have the WOT fuel burn data for the Perkins 4.236?

 

[FF]

"And I can't imagine a marine engine not capable of a continious 75% load. "

"Marine" engines , as noted come from a wide parts bin, many are not rated for cont duty.

The simple answer is to run at WOT for a min or so and simply pull back 10% in RPM .

This with most props will lower the load enough that the engine (from whatever source) will be OK for modest periods of time.

This DOES NOT work with the VW marinizations , and was risky with Yanmars that were Toyota truck parts.

The new Yanmar a BMW auto marinization might be better , but a look at the MFG HP rating table would be wise.

I would be very wary if no rating other than pleasure was given.

 

[Nomad Willy]

Fred,

This time I agree 100% with you. However it should be noted that to be ok to go to WOT and back off 10% of rpm one must be able to reach rated rpm (like 2800 for the P-4-236) to be safely loaded at 10% rpm down. And I think you're right that there are engines now (like the very high perf VWs) that should'nt be run at 75% load continuously. Perhaps Baker's Yanmar in the Pilot 30 should'nt do that either. If you're tuned John perhaps you could look in your manual and see what it says.

Flyright,

Rule of thumb is a little more than one gallon an hour for every 20hp. That should put the 4-236 at about 4.5 gph at WOT. I had a Sabre 120 (same block as the Lehman 120) and they stated 5.8 gph at WOT. The Perkins is in no way different enough to warrant different fuel burn performance but it has slightly more cu in per hp and a slightly higher engine speed so those differences should make it a wash. Using the above as a bench mark running the numbers indicates a WOT burn rate for the 4-236 of 3.2 gph. Well 4.5 and 3.2 gph numbers are'nt very close but I have more faith in the 20hp per gal rule so I'd guess the P4-236 should be very close to 4 gph. My M4-107 is about exactly half the size and I believe it's WOT burn is 1.8 gph. Is this any help? Perhaps David M can come closer but the manufacturer should have these numbers.

 

[Larry H]

My Ford Lehman 120 burns right on 2 GHP at 1600 rpm. 1600 rpm is at the peak of the torque curve, drives my 37ft boat at 7 knots and the engine and boat are very happy at that speed. If I am pushing into a strong wind or into a seaway, I increase the rpms to 1700 or 1800. That is slightly above the torque peak so as the boat slows down climbing a wave, the torque of the engine is increasing. This allows the boat to push thru the waves or into the wind without slowing down and lugging the engine.

This mode of operation was recommended by the Seattle Lehman mechanic 'guru' Norm Dibble, who has 40 years of experience with Lehmans. As he put it, "The Lehman engine is a 1950's low speed engine, and should be operated as such." Attempting to operate an old design, old technology engine, the same as a modern high speed diesel will wear it out or cause failure.

My engine now has 4500 hours on the clock.

Larry H

 

[Nomad Willy]

I knew Norm Dibble. A very good mechanic and a likable fellow. He used to give classes on how to maintain the Lehman engines. And about your experience I'm not say'in it won't work as the're are at least hundreds and probably thousands of guys with roughly the same experience as you have had. My banner now is'nt "you must run'em hard" as it has been in the past but that you CAN run'em hard. There's lots of evidence like yours that show they do'nt require 75% loading to survive but NO evidence indicating they can't gracefully sustain a 75% load. Perhaps I'll change my mind on this one too. Not likely though as most engine failures are NOT a result of a weak design. Anyway It sounds like you're at a 33% loading. Marin's loading at 50% and I'd be more inclined to favor that but in your case sucess is just that. Who put on the 4500 hrs on your engines or engine?

 

[markpierce]

On the John Deere normal-aspirated 4045 emission/qualified engine maximum torque is reached at 14000 rpm consuming about a gallon an hour while maximum rpm of 2500* consuming 4.5 gallons.* Typical load factor is shown not exceeding 65%.* Would that be something like 2.9 gallons or 2200 rpm and less on the presumption that fuel consumed equals engine loading?

*
<h2 class="sIFR-replaced" style="background-color:#ffd700;">Performance curves</h2>

*
*
<table><tbody><tr><th class="mgsperfdatatable_1"><h2 class="sIFR-replaced">Performance data</h2></th><th class="propperftablehead"><h2 class="sIFR-replaced">M2</h2></th></tr><tr><td class="mpropsubthgrey_1">Rated Power - kW (hp)</td><td class="mpropsubtdgrey">60 (80)</td></tr><tr><td class="mpropsubth_1">Rated Speed - rpm</td><td class="mpropsubtd">2500</td></tr><tr><td class="mpropsubthgrey_1">Low Idle Speed - rpm</td><td class="mpropsubtdgrey">750</td></tr><tr><td class="mpropsubth_1">Peak Torque - Nm (ft-lb)</td><td class="mpropsubtd">296 (218)</td></tr><tr><td class="mpropsubthgrey_1">Peak Torque Speed - rpm</td><td class="mpropsubtdgrey">1400</td></tr><tr><td class="mpropsubth_1">Fuel Consumption - L/h (gal/hr)</td><td class="mpropsubtd">17.5 (4.6)</td></tr><tr><td class="mpropsubth_1">*</td><td class="mpropsubtd">*</td></tr><tr><td class="mpropsubth_1">*</td><td class="mpropsubtd">*</td></tr><tr><th class="mgsperfdatatable_1"><h2 class="sIFR-replaced">M rating</h2></th><th class="propperftablehead"><h2 class="sIFR-replaced">M2</h2></th></tr><tr><td class="mpropsubthgrey_1">Typical load factor</td><td class="mpropsubtdgrey"> 65 %</td></tr><tr><td class="mpropsubth_1">Typical annual usage (hr)</td><td class="mpropsubtd"> 3000</td></tr><tr><td class="mpropsubthgrey_1">Typical full-power operation (hr)</td><td class="mpropsubtdgrey">16 of each 24</td></tr></tbody></table>
*

*

 

[Nomad Willy]

Mark,

"Typical full-power operation (hr)16 of each 24" Does that mean your engine is rated for 100% load 66% of the time? And 65% load should be 3 gph. So my engine being 1/2 size means I could cruise at 1100 rpm down from WOT and burn 1/2 gph at 23% load. Hmmmm. What does this mean Mark? " Typical load factor is shown not exceeding 65%". Sounds like they are saying not to run it over 65%??? "fuel consumed equals engine loading?" As a percentage of max burn yes.

 

[Larry H]

Eric,

I was fortunate to be able to attend two of Norm's classes. The first before I owned a Lehman and the second after the first year. By the second class, I knew what to listen to and what questions to ask.

Norm has now retired, so his classes are history.

I got my boat as the 4th owner and the engine had about 3500 hours. I received a booklet of 'maintenance instructions' written by the first or second owner that encouraged the 1600 rpm cruising speed.

I know that the engine will operate at higher speeds, but Lehmans can have an overheating problem with #6 cylinder, so moderate operation at 1/3 of max should encourage reliability. I test run the boat at max rpms for long enough to establish that the cooling system is OK, but I do that when I am near my home port, and near to Vessel Assist. I don't do that when I am up coast in your neighborhood. Are you going to be in Thorne Bay this summer? Perhaps I could swing by for a chat when I am in the area.

 

[markpierce]

Eric, I thought you were the expert.* The JD engine info came from its website.* Can't tell you more beyond the assumptions I've already made. ... It will be interesting to compare fuel consumption per the Flowscan verses RPMs and speed. ...* This summer will be very interesting when*given the opportunity to work the boat.

 

[GregJ]

Mark

http://www.deere.com/en_AU/equipment/power_systems/marine/marine_prod_gde.pdf

Your engine is rated with JD's M2 rating which develops 85HP or 63KW @ 2,500 rpm which is rated to produce full power for up*to 65% of your engine's run time, to a total of 3,000 hours per year.

If it was an M1 rating, it would be producing 75 HP or 56 KW @ 2,400 rpm and good for full power up to 24 hours a day and generally doing over 3,000 hours a year.

 

[Nomad Willy]

Larry,

Yea, I forgot about the cooling system issue. We talked about it on TF awhile back and can't remember if it was considered a design problem or a fixable problem. Considering that I'd prolly run one a bit light at least until more information was available. Perhaps they really are weak and incapable of normal full load operation. It's hard to imagine an engine that's really weak to survive in the marketplace especially as well as the Ford Lehman did.

Home? The plan is to be gone a bit more than not. Going the long way to Sitka in June and to Juneau, Icy Strait and back down Chatham Strait in August. I'm having trouble getting the boat ready so until Murphy gets out of the way .......but please stop in if you like Larry. We'd love to have you.

Mark,

"Eric, I thought you were the expert." Ha Ha ...I've got you fooled. My expertise runs of a cliff at times but if Greg sticks around perhaps we can stay on course. My knowledge is more layman like and less like an engineer at a certain point. I think the "propeller absorption" load in the graph is an approximation due to the fact that all boats are different. And I don't know how good the Flow Scan equipment is. Lots of other less expensive instruments I'd rather have as feel I know as much as need about my fuel burn. My favorite "extra" engine monitor is my Murphy Switch. It tells when coolant level is below normal. I think it already saved us once.

Greg,

I sure hope you stick around here. We need guy's like you that can pull up the facts and figures that keep us off the rocks and out of the "wives tales" dark rooms and other places one could go without cold hard facts. By "full power" do you mean WOT? That's very impressive but I suppose if they slap a turbo on the same engine it would need to be capable of that kind of performance. Perhaps the turbo version can't do WOT 65% of the time. Are you on Boat Diesel? Several of us here are (like 3 or 4) but I hav'nt spent much time there. Have'nt even got my moneys worth yet. Great site though. Or perhaps you work for JD? I think Mark has the 80hp emission engine.

 

[markpierce]

thanks, Greg.

Eric, you're still "the man."

*

 

[Larry H]

Eric,

I'll send you a PM when we get to Ketchikan. We can see how our schedules are then.

 

[stevensibs]

I have a question regarding my new engine installation. I removed a very old Cummins 160 that was hard mounted to the stringers (engine beds). The old Twin Disc gear was also hard mounted to the stringers. A normal coupling on a 1 3/4" shaft of approx 11' in length, this shaft supported by two babbit pillow block bearings evenly spaced apart, and finally a stern tube with a normal packing gland and cutlass bearing outside. The new engine is a 175 Lugger and new Twin Disc gear and I want to use engine mounts by Barry Controls or other such manuf. Can I do this and still use the old coupling and shaft system? I also want to use dripless stuffing box by PYI and get rid Of the packing gland. Thanks for your input.

 

[Nomad Willy]

Stevesibs,
We used plastic mounts by Poly Flex Australia. We took the mounts off the flywheel and moved them aft to the gear. That way very close to equal loading is felt on each mount and more pitch stability is gained. The unit is smoother than the Perkins and the rubber mounts that came out but I don't know how much of the smoothness comes from the mounts, the better location or the engine itself. Vibration wise I think all three changes played a part in the unit's preset smoothness. Try Polyflex.com

If I had it to do over (and I may) I'd go back to the traditional stuffing box.

 

[stevensibs]

Thanks. You're not the first person to tell me that regarding dripless shaft seals. I will look at Polyflex. What about the pillow block bearings? Substitute split roller bearings? They're very expensive but I wanted to get rid of the grease as the engine room is sparkling white lol.

 

[sunchaser]

Once your engine and transmission are on Barry mounts your pillow block bearings could be counter productive. You may want to post some good pictures on boatdiesel asking the same question. Tony Athens and a few others over there are masters at this stuff. Likely they can recommend a good shaft/engine setup guy near you to offer some on the ground advice.

A well set ( I'd hire a pro) up dripless unit will work fine even with the yelps and yowls from this arena. Too many think dripless means out of sight and out of mind, not so - you do have to watch them. But a good gore packing setup will not drip too much giving you some piece of mind.