Engine sync for mechanical engines....

Baker · Dec 10, 2019

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.

greysailor · Dec 11, 2019

Baker said:
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![emoji16]

menzies · Dec 11, 2019

Same set up here on my Luggers.

sunchaser · Dec 11, 2019

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.

bluebyu · Dec 11, 2019

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.

psneeld · Dec 11, 2019

Baker said:
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.

smitty477 · Dec 11, 2019

Baker said:
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.

DavidM · Dec 11, 2019

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.

David

Baker · Dec 11, 2019

sunchaser said:
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.

smitty477 · Dec 11, 2019

Baker said:
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.

rslifkin · Dec 11, 2019

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.

smitty477 · Dec 11, 2019

rslifkin said:
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?

mahal · Dec 11, 2019

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.

rslifkin · Dec 11, 2019

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.

smitty477 · Dec 11, 2019

rslifkin said:
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.

rslifkin · Dec 11, 2019

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.

smitty477 · Dec 11, 2019

rslifkin said:
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?

FoxtrotCharlie · Dec 11, 2019

We have original Glendenning Sync on our 1988 with twin mechanical Lehman 135's and it works perfectly.

Codger2 · Dec 11, 2019

Baker said:
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. :blush:

rslifkin · Dec 11, 2019

smitty477 said:
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.

smitty477 · Dec 11, 2019

rslifkin said:
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.

"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. "

Does this say that you have no experience with diesel engines and governors?

rslifkin · Dec 11, 2019

smitty477 said:
Does this say that you have no experience with diesel engines and governors?

No, it doesn't mean that at all. And in the situation of targeting equal RPM, it doesn't matter if the engines are governed or not. All that impacts is what's driving the throttle / fueling adjustments. With diesels, the governors would be adjusting fueling to maintain requested RPM. With gassers and no external synchronizer, I get to do that job manually. So if I put both throttles in the same spot and get 3250 and 3350 RPM on the 2 engines, for example, I'd just manually increase one and decrease the other to make the RPM equal, even though I may now have one engine at 65% throttle and the other at 70%.

Basically, as long as the difference isn't excessive (which would indicate a problem somewhere, like a serious prop mis-match or something damaged on one side), and the heavier loaded engine isn't overloaded, it doesn't matter if load is equal.

smitty477 · Dec 11, 2019

rslifkin said:
No, it doesn't mean that at all. And in the situation of targeting equal RPM, it doesn't matter if the engines are governed or not. All that impacts is what's driving the throttle / fueling adjustments. With diesels, the governors would be adjusting fueling to maintain requested RPM. With gassers and no external synchronizer, I get to do that job manually. So if I put both throttles in the same spot and get 3250 and 3350 RPM on the 2 engines, for example, I'd just manually increase one and decrease the other to make the RPM equal, even though I may now have one engine at 65% throttle and the other at 70%.

Basically, as long as the difference isn't excessive (which would indicate a problem somewhere, like a serious prop mis-match or something damaged on one side), and the heavier loaded engine isn't overloaded, it doesn't matter if load is equal.

I have posted zero information about gas engines in this thread.
You appear to have zero experience with these diesels.
These are unrelated posts and have little correlation.

rslifkin · Dec 11, 2019

Any pair of engines are subject to uneven loading or overloading. What's special about a diesel that makes matching RPM magically a bad idea provided the load remains within a safe range on both engines?

smitty477 · Dec 11, 2019

rslifkin said:
Any pair of engines are subject to uneven loading or overloading. What's special about a diesel that makes matching RPM magically a bad idea provided the load remains within a safe range on both engines?

We cannot compare any data as they are not comparable.
Over the years I have a few dozen emails from folks that have had problems with their diesels due to overloading/overheating.
In some cases they have shared numbers and charts that look very similar - and a most common issue is its typically one engine only.
We have no common data to compare.
This is an example of how the data does not apply...

"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."

Temperatures of a manifold or a riser will not be comparable to the center kernel that an EGT reads.

Perhaps with a gas engine there is some way to utilize a vacuum gage to see how the loads relate.
But I am not pursuing any posts or data on gas engines....

rslifkin · Dec 11, 2019

You just mentioned the key: issues from overloading. Overloading (on any engine) is bad, and yes, you should use any available metrics you have to determine if the loading on an engine is acceptable or not (some combination of fuel flow, boost, vacuum, EGT, coolant temp, oil temp, and RPM depending on what data is available and relevant to your engine).

But that doesn't change the point that it doesn't matter if the 2 engines are loaded identically (although identical would be ideal, but hard to achieve in the real world). It matters if the loading under a given condition changes over time (indicating something has changed that impacts loading) or if one engine is outside of the acceptable range. But if they're 3% off at the same RPM, but both within the manufacturer provided acceptable numbers for fuel flow vs RPM, EGT is safe, etc. then there's no problem. At that point, you just run the boat however you get the best performance and comfort, whether that's by matching engine power output / load or by matching RPM (and it'll usually be by matching RPM).

Now, of course, in the (IMO poorly designed) cases of boats with different trans ratios (and possibly correspondingly different props) on the port and stbd, there's a tougher decision: do you match engine RPM or prop RPM? If the props are pitched differently corresponding to the ratio difference, you'd probably want to match engine RPM unless that produces vibrations from the mis-matched prop RPM. However, if the props are the same pitch, then you'd want to test which match provides better boat handling and whether you get less noise / vibration with the prop RPM synched or the engine RPM synched.

smitty477 · Dec 11, 2019

rslifkin said:
You just mentioned the key: issues from overloading. Overloading (on any engine) is bad, and yes, you should use any available metrics you have to determine if the loading on an engine is acceptable or not (some combination of fuel flow, boost, vacuum, EGT, coolant temp, oil temp, and RPM depending on what data is available and relevant to your engine).

But that doesn't change the point that it doesn't matter if the 2 engines are loaded identically (although identical would be ideal, but hard to achieve in the real world). It matters if the loading under a given condition changes over time (indicating something has changed that impacts loading) or if one engine is outside of the acceptable range. But if they're 3% off at the same RPM, but both within the manufacturer provided acceptable numbers for fuel flow vs RPM, EGT is safe, etc. then there's no problem. At that point, you just run the boat however you get the best performance and comfort, whether that's by matching engine power output / load or by matching RPM (and it'll usually be by matching RPM).

Now, of course, in the (IMO poorly designed) cases of boats with different trans ratios (and possibly correspondingly different props) on the port and stbd, there's a tougher decision: do you match engine RPM or prop RPM? If the props are pitched differently corresponding to the ratio difference, you'd probably want to match engine RPM unless that produces vibrations from the mis-matched prop RPM. However, if the props are the same pitch, then you'd want to test which match provides better boat handling and whether you get less noise / vibration with the prop RPM synched or the engine RPM synched.

"It matters if the loading under a given condition changes over time (indicating something has changed that impacts loading) or if one engine is outside of the acceptable range."
Of course this is true and a good general statement but once that is said the only further value we can add is to speak about specific reading and parameters which you have not stated and would not be related to diesels.

- I am posting about diesels there is no basis of comparison for any EGT , boost, rpm or fuel flow
- many boats had non matched trans in the 80's and 90's and even later on.... do you know your "A" and "B" ratios?
- what do your prop scans show as a % difference between the two? No two props are the same and the more you look two props scanned from the same boat the more obvious it becomes.
- how do you currently measure load on your gas engines?

rslifkin · Dec 11, 2019

I've got counter rotating engines, so both transmissions run in the A position (2.57 reduction Velvet Drive 72C). And yes, I know non-matched ratios were common, but that doesn't mean it's not bad design.

My props have been prop scanned, but it was a few years ago and I don't have the numbers from it unfortunately. Based on how close the WOT RPM sits between the 2 engines (non-governed, so load directly impacts RPM at WOT), I'd say the props are close enough that if 1 was going to cause an overload, both would be overloaded.

I don't bother directly measuring load on mine (although I could add vacuum gauges, as vac vs RPM will indicate load), I just go with the rule of thumb of "as long as they reach far enough into the expected WOT RPM range without much difference between the 2 engines, cruising at below 80% of achieved WOT RPM is a light enough load to not hurt anything". Realistically, as best I can estimate, I'm pushing somewhere around 180 hp (give or take 20) per engine at cruise, out of 340 max HP. So they're not being run on the ragged edge where a slight imperfection will lead to rapid failure.

Comparing numbers between different engine models isn't very useful anyway, even with diesels. Different engines have different safe parameters.

smitty477 · Dec 11, 2019

rslifkin said:
I've got counter rotating engines, so both transmissions run in the A position (2.57 reduction Velvet Drive 72C). And yes, I know non-matched ratios were common, but that doesn't mean it's not bad design.

My props have been prop scanned, but it was a few years ago and I don't have the numbers from it unfortunately. Based on how close the WOT RPM sits between the 2 engines (non-governed, so load directly impacts RPM at WOT), I'd say the props are close enough that if 1 was going to cause an overload, both would be overloaded.

I don't bother directly measuring load on mine (although I could add vacuum gauges, as vac vs RPM will indicate load), I just go with the rule of thumb of "as long as they reach far enough into the expected WOT RPM range without much difference between the 2 engines, cruising at below 80% of achieved WOT RPM is a light enough load to not hurt anything". Realistically, as best I can estimate, I'm pushing somewhere around 180 hp (give or take 20) per engine at cruise, out of 340 max HP. So they're not being run on the ragged edge where a slight imperfection will lead to rapid failure.

Comparing numbers between different engine models isn't very useful anyway, even with diesels. Different engines have different safe parameters.

Glad it works for you - I cannot comment on gas engines but perhaps someone else will.

Alabama Boater · Dec 11, 2019

Accusync as an alternative

I replaced my Glendinning synco on my 3208 Cats with the Accusync. It operated off the flywheel mag pickup. While the control cabling is much the same as Glendinning, not needing to have drive cables made the installation cleaner. A side benefit with the higher resolution of pulses from the flywheel teeth, control rpm is +/- 3 rpm on my digital flowscan tachs. It is very easy to see fuel flow variations from my standard charted rate, engine to engine, when not in sync.

Engine sync for mechanical engines....

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