BETA Marine BD722 Vibration

[christoph]

I re-engined with a Beta 3 cylinder BD722 some 5 years ago and had no problems until this year when I Re-aligned the engine to help prevent the eating up of cutlass bearings. The alignment went OK, or so I thought. To get the optimum alignment required the raising, slightly, the front of the engine on its mounts. After that, when motoring and closing the throttle a severe vibration set in. The normal tick over speed, as set in the factory is 650RPM where all is fine. Now it on closing the throttle it stops at about 900-1000 RPM where an incredable out of balance type vibration occurs. I assume this is a primary balance problem due to the 3 cylinder nature of the engine. Briefly pushing in the stop button usually slows the engine to its normal 650RPM and no problem. Also clicking the engine into gear and the extra load will slow the engine to its smooth tick over state. I've double checked all the obvious, cables, clamps etc and all is fine. All the problems started after re-aligning the engine a little so assume this is the root of the trouble. I spoke to BETA and they have no idea but suggest the tick over is too low, I think 900RPM was suggested, although 650RPM is just as the factory set it. Also 900RPM is at the point where the bad vibration sets in. They did suggest putting spacers under the engine mounts, these would be about 10-12mm thickness. I haven't done it yet but unless somebody out there has a solution I'll try that and see what happens. Has anyone had a problem with vibration on 3 cylinder BETA's or any other 3 cylinder engines? Any help would be much appreciated.

 

[Rowana]

I'm no mechanical engineer, but it sounds more like a fuel rack problem to me.

Your 3 cylinder should be less prone to vibration than my 2 cylinder I would have thought.

Does the vibration happen when you are in, or out, of Gear?
If out of gear, I suspect it has nothing to do with your re-alignment.

Personaly I would start by checking all the fuel connections, bleed the system whether it needs it or not, change the fuel filter, and also check the mechanical linkages to the fuel rack to ensure that there is nothing "sticky" in this department.

After that, I think I'd have to call for more expert help !

 

[Stemar]

Is the throttle lever on the engine closing completely when the morse lever is returned to idle? It may appear to be fully shut, but you may be able to push it a bit further to get the proper idle speed. If so, the problem's in the lever or cable, or their adjustment.

As for the vibration, raising the engine puts more strain on the mountings. Has one of them come apart? It wouldn't necessarily be obvious when the engine's sitting on it.

Good luck!

 

[stevebirch2002]

I was always under the impression that a three cylinder engine will be smoother than the two cylinder. Youneed to check if the vibration is till there out of gear. The idle revs should be 850 - 900 rpm.

 

[cliff]

You say you raised the front of the engine but did you check both front mountings are properly loaded. In 4 point support, as in your arrangement it is important that the mountings are correctly adjusted to achieve correct loading and elevation.

If you screw up the starboard side front mounting the engine will rise slightly with the increased compression of the mounting and the post side mount will suffer a reduction in compressive loading. If the mounting loads are not balanced you can have severe vibration problems.

It is difficult to explain in words but it is as if the engine was balanced between, for example, the front starboard and rear port mounting (in high compression loading) and rocking between the front port and starboard mountings (in lower compression).
--------------------

"Artificial intelligence is no match for natural stupidity"

 

[christoph]

Hi Rowana and thanks for the reply. The vibration ONLY occurs when going to neutral and therefore out of gear. Clicking the Morse into drive, either forward or reverse puts enough load on the engine to slow it down to its non vibration revs. Stabbing the stop button has the same effect. Although occasionally, when the engine has been running for a while I noticed even after slowing it down, using the above methods, it will sometimes increase revs back up to the vibration condition. I have changed the fuel filter and bled the system. All the connections, fittings are OK. I have even gone down to the engine when it has the vibs and closed the throttle manually against the stop, where it was anyway, all to no avail.

 

[christoph]

Hi Stemar and thanks for the reply, Yes the throttle is closing fully. As Explained I’ve been down to the engine and closed the throttle manually, although it was closed anyway, and it makes no difference. As for the mountings I fitted two new ones at the front when I realigned the engine. As it happens there was nothing wrong with the old ones.

 

[christoph]

Hi stevebirch 2002 Thanks for the reply, Yes BETA said the revs at tick over should be 900RPM but the 650RPM was set at the factory and I have a data sheet that came with the engine that says Idle is set at 650 RPM. They must have changed the specification

 

[christoph]

Hi Cliff and thanks for the input. I think what you say may be the closest to solving the problem. I did notice when I adjusted the engine on the mountings one of them was slightly out of alignment with the others. Thgis had been done when the engine was replaced with the BETA. It appeared to have collapsed but when I took it out to replace it it was OK just squashed down at the front due to the slight mis-alignment. I replaced them both anyway. Next year when I get to the boat in May (its in Greece) I will re-align the errant mounting and see how that goes. Having said all that I can't see how being out of alignment would necessarily apply uneven load. But we will see! many thanks to all for the input from all. Chris yacht Rapport Lady.

 

[bob_tyler]

Presuming that you have a rev counter, have you tried letting the engine down to 650. Then, go in gear and slowly rev up through the 900 vibration period and see if it vibrates when it goes through those revs.

If it doesn't vibrate while accelerating under load, suspicion must fall on the engine mounts. Either they are unevenly compressed or one is broken. It is nothing to do with alignment.

 

[christoph]

Hi Bob and thanks for your thoughts on my vibration. I have done exactly what you describe ie got the revs at 650 and tried to slowly increase the revs and at around 900-950 the engine goes through the severe vibration phase. Strangely, you can't keep it at those revs and the vibs by using the throttle. The engine will vibrate, briefly, and then settle at a slightly higher setting where the vibration is nil. I think you are right and the cause is to do with the mounts, two of which I have replaced. Many thanks for your interest Chris Howe ( Yacht Rapport Lady)

 

[Scomber]

Bump!!!
Are most of your beta 25's idling at 850 or 900 rpm?
Got some vibs at 850 Beta say ok to increase to 900 - anyone done this and noticed less vibs when idling?
Thanks

 

[RichardS]

Bump!!!
Are most of your beta 25's idling at 850 or 900 rpm?
Got some vibs at 850 Beta say ok to increase to 900 - anyone done this and noticed less vibs when idling?
Thanks

Are you measuring that idling speed with a digital laser tachometer or just reading it from the rev counter? If it's from the rev counter it's probably not accurate to 50 rpm either way.

Richard

 

[Scomber]

Hadn't thought of that - you got a digi laser tachometer? Recommend a type/model that would be good enough for this? Screwed screw in a bit seemed to be running slower - did I go the wrong way?? Thanks anyway!

 

[RichardS]

Hadn't thought of that - you got a digi laser tachometer? Recommend a type/model that would be good enough for this? Screwed screw in a bit seemed to be running slower - did I go the wrong way?? Thanks anyway!

This is the one I bought. Easy to use and very accurate. I found out that one of my rev counters reads 150 - 200 rpm more than the other. No wonder I always used slightly more fuel on the fast side.

Richard

 

[Scomber]

Thanks - which one was it ?

 

[Neil Spooner]

Hi Christophe,

I have a fried who has the same problem as you......did you resolve the problem, and if so how?

Thanks

Neil

 

[LittleSister]

Hi Christophe,

I have a fried who has the same problem as you......did you resolve the problem, and if so how?

Thanks

Neil

One would hope he's solved it in the last 14 years! (The thread dates from 2005.)

Cristophe hasn't been on the forum during the last year, so i doubt we'll find out.

The various advice provided here will hopefully help your friend tackle the issue, though.

 

[PetiteFleur]

Bump!!!
Are most of your beta 25's idling at 850 or 900 rpm?
Got some vibs at 850 Beta say ok to increase to 900 - anyone done this and noticed less vibs when idling?
Thanks

I increased the idle speed to 900 rpm recently as it sometimes stalled - on advice from Beta, original setting was 850rpm. I also had to replace one of my rear mounts after I realigned the engine after realigning the P bracket. The mount had come unstuck. Cured the vibration I had.

 

[Neil Spooner]

Thank you for the info.
It frustrates me when people post questions, people take the time to reply, & then when they get or find the answer they don’t post it!