Electrical problem Benneteau 36cc alternator

P

Pyramid

Active Member
Joined
30 Nov 2012
Messages
48
Location
Chatham
Visit site
I have recently purchased a benneteau 36 cc equipped with Volvo Penta MD2040 - and very happy with her I am. However, when using the other day I had this problem: Engine running in neutral whilst preparing to slip the mooring. Mooring slipped and engine engaged and revs increased. Then audible alarm sounds. Sea cock definately open. No blockage. Engine still running and operating as expected. Into neutral, audible alarm stops. Engage gear again and under load, the audible alarm sounds. Additionally, when the alarm sounds, the rev counter/tacho falls to zero - as if engine stopped. Engine - of course still running well. Thoughts are that there maybe a problem with the alternator regulator. Has anyone experienced this symptom or have any ideas?
 
simon-tracey said:
I have recently purchased a benneteau 36 cc equipped with Volvo Penta MD2040 - and very happy with her I am. However, when using the other day I had this problem: Engine running in neutral whilst preparing to slip the mooring. Mooring slipped and engine engaged and revs increased. Then audible alarm sounds. Sea cock definately open. No blockage. Engine still running and operating as expected. Into neutral, audible alarm stops. Engage gear again and under load, the audible alarm sounds. Additionally, when the alarm sounds, the rev counter/tacho falls to zero - as if engine stopped. Engine - of course still running well. Thoughts are that there maybe a problem with the alternator regulator. Has anyone experienced this symptom or have any ideas?
Click to expand...

When the alarm sounds do any warning lights show? Do you have any information on battery voltage a) when idling, b) when alarm is sounding that supports your regulator theory?

You might get a better response by posting this on PBO.
 
I would check that the drive belt for the alternator is tensioned correctly. On a VP 2003 I have seen something similar happen when the pivot bolt holding the alternator snaps leaving the alternator hanging - various alarms go off and the rev counter drops to zero.
 
Similar but not identical. That engine has a warning buzzer but its triggered by any of oil pressure, chargeing and water temp. So you have to look at the warning lights to see what is causing the problem.

However, the revs drop / ok in neutral bit is odd. The only connection I can think of between an electrical problem and the engine being in or out of gear is something binding on the shaft / prop , dropping the engine speed below the normal idle level and triggereing the charge alarm. But then why should the rev counter drop to zero?

It could simply be an intermittent loose connection triggered by engine movement. I would start at the batteries and work my way to the engine making sure all connections are tight and clean. I would do the same behind the volvo instrument panel and I would look to make sure that some wire somewhere had not been chafed. Slipping fan belt?

Dont see it being the regulator but you can check that by clipping a voltmeter onto the nbattery posts and making sure the voltage goes up to more than 13.5 v with engine running.

My problem is an occasional beep from the alarm when the engine is idling - not yet found the cause.
 
My Oceanis 381 sometimes does a similiar thing on start up, have to blip the throttole on start up to get the rev counter working and all is fine.
 
Re my electrical problem thankyou all. Today, I took someone to the boat that understands these things and we found: The drive belt was fine; oil pressure correct; voltage at battery 13.2 or thereabouts increasing 14.6 on increased engine revs - which maybe too high. Sod's law featured. so, alarm did not sound at all other then when it is supposed to. The whole electrical system checked and found to be operating correctly and charging properly. This appears to be an intermiitent fault - which does not help.
Particularly interested that 'jac' who has recently bought a 36cc, said that his boat did the same. Likewise previous owner of my boat said that this happened occasionally and that he would fire up the radar. He believed that the alternator was slightly overcharging and putting on the radar would draw power and the alarm would go off.
I will have to 'suck it and see' for a while and then take the alternator to an electrical engineer. Many thanks again. Not cured yet though.
 
Some posters here seem to be referring to an alternator that needs a kick of the throttle to get going initially, that's different from your problem I think. (They could benefit from a higher pulley ratio.)
You (OP) are inferring that the altenator is running OK (engine revs are indicated) before slipping it into gear, at which time indicators die, although the engine is physically performing to spec. I think you may have an electrical problem, but not the regulator or alternator as a whole, since you have a healthy (it's not too high) charge voltage present - but no revcounter _ that means the "W" wire from the alternator (raw AC) isn't getting to the revcounter - or -more likely , as you have alarm noises, either of the feeds (plus or minus) is getting lost from the rev counter and the alarm sense system. I'd bet on a negative feed somewhere, but just check out everything in that area.

Don't think type of boat or engine, this can happen to anyone!
 
Thank's Billjratt - I'll take this advice to my electrical engineer mate, who has knowledge of these things and go from there. I will have to put the radar scenario to the test at some time, although, obviously, I don't want to have to have the radar on. Thank you again.
 
simon-tracey said:
Thank's Billjratt - I'll take this advice to my electrical engineer mate, who has knowledge of these things and go from there. I will have to put the radar scenario to the test at some time, although, obviously, I don't want to have to have the radar on. Thank you again.
Click to expand...

I really can't see how switching on the radar could cure any electrical fault: what's reported is at best coincidence. Many years ago Des Sleightholme had a story about an outboard motor that would only start when the fore hatch was opened...

My money's on Biljratt: there is probably a poor connection somewhere in the control wiring, probably the negative, most likely at the engine end, which occasionally goes open circuit when there is a change of engine vibration.
 
You will probably find a group of negatives near the starter motor attached to the engine by a bolt.
I would remove the bolt, clean the negative connections and try again.
 
I hope this is not common to all Beneteau 36ccs as we have just had our offer price for one here in the uSA accepted, mind it does have a Yanmar not a Volvo and even that has been fitted with an uprated 150A alternator, so maybe we will dodge the bullet.
 
simon-tracey said:
I have recently purchased a benneteau 36 cc equipped with Volvo Penta MD2040 - and very happy with her I am. However, when using the other day I had this problem: Engine running in neutral whilst preparing to slip the mooring. Mooring slipped and engine engaged and revs increased. Then audible alarm sounds. Sea cock definately open. No blockage. Engine still running and operating as expected. Into neutral, audible alarm stops. Engage gear again and under load, the audible alarm sounds. Additionally, when the alarm sounds, the rev counter/tacho falls to zero - as if engine stopped. Engine - of course still running well. Thoughts are that there maybe a problem with the alternator regulator. Has anyone experienced this symptom or have any ideas?
Click to expand...

There may be water flow but this may be insufficient in volume under load. If the boat has not been used for some time then deposits may have built up in the cooling system and you need to follow the flow of water through the motor and if necessary dismantle and clean each section. I had a similar problem two years ago but had the luck to be moored beside a "mécanicien extraordinaire". With the engine running he was able to put his hand on different parts of the engine and, by feeling the temperature was able to identify where the problem was.
 
You must log in or register to reply here.

Share this page

Top