Yanmar 1GM10 with loose fanbelt , how much play should there be ?

I was taught you should just be able to twist the belt by 90 degrees. Works for me, I have a Yanmar YSB8G
 
hopern1 said:
I have an old Yanmar 1GM10. Below is a you tube video I have just uploaded of it.

Question to forumites is ? Is this correct ? Or should it be tighter. And if so , how much slack should there be ?

http://youtu.be/xYvOzB84VRc
Click to expand...

No where near tight enough !!!!!! By miles. Its practically falling off

With moderate thumb pressure you should be able to deflect the belt by about 1 cm mid way between the pulleys.**

Twisting through 90° as suggested by Camella is the way to test flat belts like poly V belts, or even cam shaft drive belts until they can be properly tensioned with a gauge

**Edit I remembered I have a w/shop manual down loaded ... thats what it says in there . You know what they say, "RTM".
 
Last edited:
 
Twister_Ken said:
You have a fan on a Yanmar? Mine just has an alternator.:o
Click to expand...

My alternator has a fan!

Back on topic, I have found it impossible to keep my 1GM10 belt as tight as Vic S correctly quotes the manual as specifying ... if I do tighten it up that much it's looser again next time I check. However, it's happy to stay at "90 degree twist in the middle of the longest run" tight, and seems to work well at that. That's also the setting for the plethora of vee belts on my Citroën DS.
 
JumbleDuck said:
My alternator has a fan!

Back on topic, I have found it impossible to keep my 1GM10 belt as tight as Vic S correctly quotes the manual as specifying ... if I do tighten it up that much it's looser again next time I check. However, it's happy to stay at "90 degree twist in the middle of the longest run" tight, and seems to work well at that. That's also the setting for the plethora of vee belts on my Citroën DS.
Click to expand...

Whilst I agree in principle with VicS, he's destined for serious disappointment with all Yanmar belt systems. In fact apart from being too slack the belt is worn out and running at the bottom of the pulley V. By changing the ghastly Yanmar/Hitachi alternator pulley from pressed tin to a solid one one can work transformations.
Of course the only reason the the pulley is going round is because there's no load on the alternator, either because the regulator hasn't yet kicked in or, more likely, because the the alternator is not connected to a battery.
Yes Hitachi's do tend to overheat and melt - but most have a fan, usually an inefficient little internal one.
12mm is a more achievable deflection figure, because of the length of the free run.
Overtightening just causes the alternator bearing to shake, rattle and roll.
As for raw-water pumps on Yanmars, don't ever attempt to tighten the belt to the VicS 10mm. You'll spend a fortune on new bearings for the pump. I find about 20mm about right, despite the distance only being about 100mm. That applies to the GM and YM series I've had.
 
charles_reed said:
Whilst I agree in principle with VicS, he's destined for serious disappointment with all Yanmar belt systems. In fact apart from being too slack the belt is worn out and running at the bottom of the pulley V. By changing the ghastly Yanmar/Hitachi alternator pulley from pressed tin to a solid one one can work transformations.
Of course the only reason the the pulley is going round is because there's no load on the alternator, either because the regulator hasn't yet kicked in or, more likely, because the the alternator is not connected to a battery.
Yes Hitachi's do tend to overheat and melt - but most have a fan, usually an inefficient little internal one.
12mm is a more achievable deflection figure, because of the length of the free run.
Overtightening just causes the alternator bearing to shake, rattle and roll.
As for raw-water pumps on Yanmars, don't ever attempt to tighten the belt to the VicS 10mm. You'll spend a fortune on new bearings for the pump. I find about 20mm about right, despite the distance only being about 100mm. That applies to the GM and YM series I've had.
Click to expand...


Obviously , at least its obvious to me, if the belt is so worn that its running on the bottom of the V it should be renewed, and then correctly tensioned.

With fresh water cooled engines the manual still stipulates 10mm deflection but on the shorter belt run between the water pump and alternator pulleys. Effectively this is a lower tension than the same deflection on the longer belt runs.

according to the manual the belt for belt driven raw water pumps should be tensioned so that the deflection under moderate finger pressure is 6mm.

Moderate finer pressure really requires defining as a hairy-arsed mechanic will have a totally different perception of "moderate pressure" to some wimp in an office who finds operating a touch screen computer heavy going.
FWIW 8kg is suggested in my car workshop manual. I guess it will need a fairly hairy a*se to deliver that much force with a finger or thumb.... its certainly a lot more than a touch screen needs :)
 
On the 1GM the belt only drives the alternator, the pump is gear driven. That belt is either the wrong belt or the adjuster is at the lowest limit. Never had any trouble keeping mine tensioned to the recommended 1cm deflection, but you need to be a bit of a contortionist to get the adjustment right. Don't have it too tight or you will get a spray of black dust as the belt wears on the cheapo pulleys. Helps if you keep the pulleys clear of rust.
 
Take the belt to your friendly neighbourhood auto factor and get something the same length. My Yanmar belts do not keep tension (1/2" slack) and I got one from my factor for £3.00 or so. It takes up slack and hasn't eased off since I fitted it, but it is a "toothed" belt rather than a simple fee. I took my "spare" belt which is still in my toolbox. I did post the part number but cannot find my post so can't advise further.

Anyone got any ideas about a generic alternator? My Hitachi is working well but my auto-electrician cannot open it to replace the brushes due to corroded bolts.
 
I have always tended to err on the loose side - say 1.5 inch total deflection. As long as it's tight enough to do its job, then it's fine. If the battery is charging and the engine is running at normal temperature, then it's doing its job.

If you err on the tightish side, and I suggest that 2cm total deflection is a bit on the tight side, you have to keep adjusting it again and you risk extra wear on the bearings.

That's probably not very sound engineering-wise, but its served me well for 40 years.

Richard
 
I didn't even start the video because I could see from the still that the belt was much too loose! Some of the posts on here really worry me. If someone has to video a problem and ask for advice what are they going to do in a real incident? Read the manual, think what may go wrong, check before you go out. If you aren't practical get / pay someone else to sort it out or show you how to. In fairness, perhaps that is exactly what the OP is doing but I do wonder sometimes!
 
You really do need to get to know your engine, even just basic things.

See the 2 links for operators and basic service manuals:

http://clubfantasia.org/images/stor...ce Manual_1GM(10L) 2GM(F)(L) 3GM(D)(F)(L).pdf

http://clubfantasia.org/images/stories/1gm10/Yanmar.gm-series.pdf

Download and keep a copy on a PC/Laptop or Tablet that you can take on the boat with you.

I intimately know a 1GM10 unit (ask Bav34!!) after a love/hate affair with the one in Zara, but now I love the engine and find it very reliable and a joy to work on.
If you want to do a bit of routine servicing, service kits are available on Ebay for about £35 so no excuse not to have a spares kit onboard.
Happy to show you the basics on servicing over the winter if you want to, you will have to come over to Langstone for me to show you though!

hopern1 said:
I have an old Yanmar 1GM10. Below is a you tube video I have just uploaded of it.

Question to forumites is ? Is this correct ? Or should it be tighter. And if so , how much slack should there be ?

http://youtu.be/xYvOzB84VRc
Click to expand...
 
Hi there,
I come to boats and engines with nothing but enthusiasm and a desire to learn. No history or experience. (apart from a lot of time on the water windsurfing before kids arrived, more than a decade ago).

So, it is as you call it at the end of your response, I am learning as I go along. I am sure along the way I will ask incredibly stupid questions but I hope that the wisdom of the collective forumites will save me from any catastrophes and make me a better sailor.
 
Hadenough said:
I didn't even start the video because I could see from the still that the belt was much too loose! Some of the posts on here really worry me. If someone has to video a problem and ask for advice what are they going to do in a real incident? Read the manual, think what may go wrong, check before you go out. If you aren't practical get / pay someone else to sort it out or show you how to. In fairness, perhaps that is exactly what the OP is doing but I do wonder sometimes!
Click to expand...

I have posted similar thoughts often and normally get some illogical answer about not knowing what happens under their car bonnet either. I find it frightening that people will set off in a boat with no knowledge-base to call on if there should be problems. Boats rarely just stop safely and wait until the RAC arrive.

hopern1 said:
Hi there,
I come to boats and engines with nothing but enthusiasm and a desire to learn. No history or experience. (apart from a lot of time on the water windsurfing before kids arrived, more than a decade ago).

So, it is as you call it at the end of your response, I am learning as I go along. I am sure along the way I will ask incredibly stupid questions but I hope that the wisdom of the collective forumites will save me from any catastrophes and make me a better sailor.
Click to expand...

Everyone has to find out things as they grow in experience. However there are quite a lot of things on boats which could be regarded as essential knowledge. If you don't have the knowledge yet I would certainly suggest getting the whole boat looked-over by someone with experience. Not necessarily paying someone, but get to know people who may be able to advise.
It could be that "stitch in time" you may need.
 
charles_reed said:
Whilst I agree in principle with VicS, he's destined for serious disappointment with all Yanmar belt systems. In fact apart from being too slack the belt is worn out and running at the bottom of the pulley V. By changing the ghastly Yanmar/Hitachi alternator pulley from pressed tin to a solid one one can work transformations.
Click to expand...

Where do you source an improved pulley? This sounds like a good idea.
 
Easy enough to get. You need to know the various dimensions of course.


04181.jpg


They often come with a 17mm hole and have a 15mm sleeve in that so it will fit either diameter shaft.

I sold one a while ago for £5.

This ebay shop has them http://www.ebay.co.uk/itm/Alternator-Pulley-Belt-type-B-/390817231148?_trksid=p2054897.l4275

In the USA they are often $5, but the hassle of sending one back that was wrong is just not worth the effort.
 
Last edited:
You must log in or register to reply here.

Share this page

Top