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Old 12-10-2019, 11:03 PM   #1
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Engine sync for mechanical engines....

I struggle not to type "prop sync"...but alas.... I know Glendenning is the leader in this market segment. I just bought me a new boat(to me) and it has a pair of twin Cummins 6CTAs that I am thrilled about. THe one issue is I struggle to sync them by ear. The friction on the power levers are a little loose....not sure if that is the issue. But damn it drives me crazy.

Sooooo....first off, I am curious as hell how this system works on mechanical engines. In my head it seems like it would be very complex....but obviously it is not. Second off....is it expensive and/or dificult to install?? Like I said, my new-to-me boat is impossible to sync. THanks in advance.
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Old 12-11-2019, 12:04 AM   #2
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Quote:
Originally Posted by Baker View Post
I struggle not to type "prop sync"...but alas.... I know Glendenning is the leader in this market segment. I just bought me a new boat(to me) and it has a pair of twin Cummins 6CTAs that I am thrilled about. THe one issue is I struggle to sync them by ear. The friction on the power levers are a little loose....not sure if that is the issue. But damn it drives me crazy.

Sooooo....first off, I am curious as hell how this system works on mechanical engines. In my head it seems like it would be very complex....but obviously it is not. Second off....is it expensive and/or dificult to install?? Like I said, my new-to-me boat is impossible to sync. THanks in advance.
Howdy John....congratulations on the new ride!
I have mechanical John Deeres on Salty, with Glendenning synchronizers. As you can see in the picture, a mechanical "speedometer cable" drive cable runs from the front of each engine to the actuator unit mounted above the port engine. Mechanical control cables run from the actuator to each engine's injector pump and to the upper and lower helm throttle levers.
All it takes is $ and time to install!Click image for larger version

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Old 12-11-2019, 06:34 AM   #3
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Same set up here on my Luggers.
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Old 12-11-2019, 06:51 AM   #4
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Baker
Glendinnings work just fine. Are your tachs accurate/digital? Aetna provides good numbers for synchronizing manually. Provided you can get your power levers to stay set.

Rube Goldberg alert - Years ago I had a SeaRay with a slipping power lever, with a few hits and misses I got the right internal spring adjustment to keep it set better. The ultimate solution though was to install a light tension spring on the throttle (gas) cable at the engine.
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Old 12-11-2019, 06:57 AM   #5
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Adding to Greysailor's well written post;

On my boat:
The "throttle" cable for the "master" engine goes from the helm to the engine.
The "throttle" cable for "slave" engine goes from helm to the sync unit.
The "throttle" cable to control the slave engine goes from the sync unit to the slave engine.

Mechanically, the sync unit changes the speed setting of the slave to match the master.
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Old 12-11-2019, 07:26 AM   #6
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Originally Posted by Baker View Post
I struggle not to type "prop sync"...but alas.... I know Glendenning is the leader in this market segment. I just bought me a new boat(to me) and it has a pair of twin Cummins 6CTAs that I am thrilled about. THe one issue is I struggle to sync them by ear. The friction on the power levers are a little loose....not sure if that is the issue. But damn it drives me crazy.

Sooooo....first off, I am curious as hell how this system works on mechanical engines. In my head it seems like it would be very complex....but obviously it is not. Second off....is it expensive and/or dificult to install?? Like I said, my new-to-me boat is impossible to sync. THanks in advance.

John...I was the Glendenning service guy for the marine electronics place I worked for.


Unless they have changed the design (which I guess would only be for the better knowing that company)...it is actually simple in design and pretty robust.


The most common problems I found were usually installation problems resulting in early failure (like cable bends too tight)...so choose an installer wisely or review the install against "book" guidelines.


Thus ....while it is straigtforward to install, placement of parts and running of cables can be frustrating and you have to measure the cables (like shift/throttle control cables) pretty accurately before ordering. Otherwise, fiddling with distances and cable loops can be frustrating and some give up and thus the cable kinks/wear.



Again, dated info, but recent boater reports seem to support my high opinion of the company and it's customer service.
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Old 12-11-2019, 07:37 AM   #7
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Originally Posted by Baker View Post
I struggle not to type "prop sync"...but alas.... I know Glendenning is the leader in this market segment. I just bought me a new boat(to me) and it has a pair of twin Cummins 6CTAs that I am thrilled about. THe one issue is I struggle to sync them by ear. The friction on the power levers are a little loose....not sure if that is the issue. But damn it drives me crazy.

Sooooo....first off, I am curious as hell how this system works on mechanical engines. In my head it seems like it would be very complex....but obviously it is not. Second off....is it expensive and/or dificult to install?? Like I said, my new-to-me boat is impossible to sync. THanks in advance.
At hull speeds it does not matter too much but at higher cruising speeds and loads we would always syc with the boost gages as they would allow the engines to be loaded near identical.
We did have props tuned to S1 specs but even then the rpm would be about 50 different (at say 2,500) to get equal loading.
The pyro's would confirm equal loading as would the fuel consumption gages we had on one of the boats.
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Old 12-11-2019, 09:36 AM   #8
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Curious how you are attempting to sync: by rpm or by ear. IMO if you can't hear the beat of different rpm engines, why bother trying to sync by rpm or otherwise. In the few twin engine boats I have operated, I really couldn't hear much of a beat. Just get them close and all is good.

But if the beat is noticeable and the throttle slop makes it difficult to get it right, Glendinning synchronizers will solve the problem because as noted above, they work directly on the governor.

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Old 12-11-2019, 09:37 AM   #9
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Baker
Glendinnings work just fine. Are your tachs accurate/digital? Aetna provides good numbers for synchronizing manually. Provided you can get your power levers to stay set.

Rube Goldberg alert - Years ago I had a SeaRay with a slipping power lever, with a few hits and misses I got the right internal spring adjustment to keep it set better. The ultimate solution though was to install a light tension spring on the throttle (gas) cable at the engine.
The tachs are not accurate. I dont sync to the tachs...I sync it by ear....wah wah wah waaaaaaaaaaaaahhhhhh. Well aware of Aetna digital tachs as I have them on my current boat. Likely the first mod I will do on this boat. I will have to redo my panel though as the tachs are huge on this boat so I would need something to fill that hole. Anyway, maybe digital tachs and some tension adjustment might be all I need. I can sync my current boat and it will stay that way all day if I let it. I honestly think there are some other harmonics going on with this boat that might make it sound out of sync when maybe it isn't.

As far as syncing by boost....no way. 50rpm difference would be maddening. My current boat I am always within +/- 5rpm. I don't know what kind of boost gauges you have but my tachs are significantly more accurate than my boost gauges. Boost gauges should be a reference to the health of the engine(like oil pressure)....and not a primary source for setting power....that is strictly my opinion.
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Old 12-11-2019, 10:18 AM   #10
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The tachs are not accurate. I dont sync to the tachs...I sync it by ear....wah wah wah waaaaaaaaaaaaahhhhhh. Well aware of Aetna digital tachs as I have them on my current boat. Likely the first mod I will do on this boat. I will have to redo my panel though as the tachs are huge on this boat so I would need something to fill that hole. Anyway, maybe digital tachs and some tension adjustment might be all I need. I can sync my current boat and it will stay that way all day if I let it. I honestly think there are some other harmonics going on with this boat that might make it sound out of sync when maybe it isn't.

As far as syncing by boost....no way. 50rpm difference would be maddening. My current boat I am always within +/- 5rpm. I don't know what kind of boost gauges you have but my tachs are significantly more accurate than my boost gauges. Boost gauges should be a reference to the health of the engine(like oil pressure)....and not a primary source for setting power....that is strictly my opinion.
I have many examples but here is one with the Cummins 6c's....
Cruising from Northport to Mystic one summer with a friend who had a 46 Sea Ray with the 450 6C Cummins.
He was on sync and at about the 4 hr mark his port side engine began to black smoke pretty bad.
We slowed for the rest of the trip and when in port we eventually found a slit in his flex hose between the turbo and intercooler.
So that engine gradually lost rpm and the sync age was making up fuel to match the rpm's.

"I don't know what kind of boost gauges you have but my tachs are significantly more accurate than my boost gauges."
Your tachs tell you nothing about the load on the engines - the most important thing you can know.
Any variation in props as tuned, growth on the props or anything you pick up along the way will unbalance the load between the engines.
The engine which becomes overloaded will be subject to damage much sooner then you might think.

"and not a primary source for setting power"
You cannot set power with a tach especially on a twin engine application - if you have ever down that you likely know from the unbalanced fuel usage.

FWIW - I really liked the Cummins 6c's in our friends boat , a great engine.
Things to check are the typical aftercooler maintenance, aftercooler leaks/cracks at the bottom zinc ,and the bottom turbo coolant banjo bolt for leaks. Pretty minor know issues for that engine IMHO.
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Old 12-11-2019, 10:26 AM   #11
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Fuel flow and boost are useful for setting the engines to equal power, but in the real world, provided there's no large power imbalance that would be concerning or damaging, I'd rather sync to equal RPM and accept a small power imbalance. It ends up sounding and feeling smoother that way.
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Old 12-11-2019, 10:35 AM   #12
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Fuel flow and boost are useful for setting the engines to equal power, but in the real world, provided there's no large power imbalance that would be concerning or damaging, I'd rather sync to equal RPM and accept a small power imbalance. It ends up sounding and feeling smoother that way.
I am curious what your best prop scan job had as a difference in % between the two props?

Then if you were to run at say 2,500 rpm how would that difference equate to rpm?

Even if the props and trans were perfectly matched between the two - what happens after a time when one prop has a few barnacles and the other is clean?
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Old 12-11-2019, 11:10 AM   #13
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I have Aetna digital tachs and no synchronizer. Although I have no issues syncing the engines, the Glendenning synchronizer is something I miss from my previous boat. I got so used to operating just one throttle lever that having to operate two is now awkward.

Before you switch to those Aetna's, check pricing. If you have to buy four of them, it might be less expensive to have a glendenning unit installed.
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Old 12-11-2019, 11:12 AM   #14
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You're absolutely right that you'll never get engine load perfectly equal at a given RPM. But provided neither engine is being overloaded, a small imbalance isn't a problem. It'll just cause slightly uneven fuel consumption. On the other hand, the constant pulsing noise and sometimes extra vibration from twins running at different RPM (more noticeable on higher revving engines and with higher shaft speeds) can drive someone crazy.
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Old 12-11-2019, 11:48 AM   #15
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You're absolutely right that you'll never get engine load perfectly equal at a given RPM. But provided neither engine is being overloaded, a small imbalance isn't a problem. It'll just cause slightly uneven fuel consumption. On the other hand, the constant pulsing noise and sometimes extra vibration from twins running at different RPM (more noticeable on higher revving engines and with higher shaft speeds) can drive someone crazy.
"You're absolutely right that you'll never get engine load perfectly equal at a given RPM. But provided neither engine is being overloaded, a small imbalance isn't a problem. It'll just cause slightly uneven fuel consumption."


How do you detect if they are overloaded or not?
I do not know how long you have had diesels or whether you have had a long relationship with EGT and boost gages on diesels. If you are going to run at cruising speeds utilizing the upper half of your diesels hp range I would propose some thoughts.
Here are a few thoughts:
- what exactly does your prop scans say about your prop balances in %
- if this is an older boat with older trans what are the "A" and "B" ratios on your trans
- do your diesels reach rated RPM on a fully loaded boat with a typical bottom when hot and humid + 3-5%
- are your tachs known accurate, have you strobed them?
- does your EGT fall within acceptable range throughout the entire rpm range?

With all the above said and OK - if your rated rpm is say 3,000 rpm and you are cruising at say 2,400 with equal boost what would happen if you purposely altered the RPM by 50 or more?
How much would your Boost change? What happens to the EGT?

Most folks do not have the instruments to know that they Are affecting their engine health and life.
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Old 12-11-2019, 11:50 AM   #16
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If both engines are capable of reaching rated RPM and especially if you have an EGT gauge and can see that it's in the safe range, you can be fairly confident that you're not overloading one engine even if one has slightly more load than the other at a given RPM.
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Old 12-11-2019, 12:02 PM   #17
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If both engines are capable of reaching rated RPM and especially if you have an EGT gauge and can see that it's in the safe range, you can be fairly confident that you're not overloading one engine even if one has slightly more load than the other at a given RPM.
What engines do you have? Where are the EGT probes located? (pre or post turbo and where)
What RPM do you cruise at? At that cruise what is your boost numbers Pt and stb?
What happens to the EGT reading when you sync by rpm vs boost?
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Old 12-11-2019, 12:10 PM   #18
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We have original Glendenning Sync on our 1988 with twin mechanical Lehman 135's and it works perfectly.
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Old 12-11-2019, 12:17 PM   #19
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THe one issue is I struggle to sync them by ear. The friction on the power levers are a little loose....not sure if that is the issue..
Most mechanical shifters (Morse, etc) have a friction adjusting device to overcome this looseness you speak of. Having had that exact experience, but also having MicroCommander shifters, I finally bit the bullet and had a pro come out and adjust the electronic boxes above both engines. The sync works now but no where near as well as my buddy's Glendennings. I synced my boat for 4 years by ear and didn't mind it much. When I was flying multi engine prop planes I synced them almost exclusively by ear which became a habit. Syncing a boat, however, seems to be more of a challenge than synching a plane.

Advice: If you are planning to add a synching system, give the Glendenning people a good look.
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Old 12-11-2019, 12:31 PM   #20
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What engines do you have? Where are the EGT probes located? (pre or post turbo and where)
What RPM do you cruise at? At that cruise what is your boost numbers Pt and stb?
What happens to the EGT reading when you sync by rpm vs boost?
My current boat has non-turbo gassers, so boost isn't applicable. And no EGT gauges on them other than me climbing into the engine room and shooting the couple inch non-jacketed portion of the manifolds with an IR gun.

Going by fuel use, my stbd engine is under slightly higher load than the port with both cruising at 3300, but it's within a couple percent. Both turn within a few RPM of each other at WOT though, so there's nothing about it that concerns me. And yes, my tachs are calibrated. There's a significant difference in pleasantness at the helm with them humming along in sync vs having them 50 or 100 rpm off, so as long as they're both happy, both make appropriate RPM wide open, etc. I have no reason to intentionally run them out of sync just to get fuel use and load perfectly even.
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