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Old 06-05-2020, 04:33   #1
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Alternator

Well, this past saturday I went out for a day sail and on the way blew out a coolant hose on the engine... of course I didnt know it till the overheat alarm came on.... When I went below, there was water everywhere including about 1/4 inch deep on the cabin sole.

Fortunately there was enough slack in the hose to cut off the blown out part and reconnect it to the heath exchanger.

The bad news is that it fried my alternator..

Has anyone found a decent replacement for the Hitachi LR-155 alternator for a 2GM20F?

Im looking all over the internet and see alll sorts of no name units bu not sure that any would be suitable for a marine environment and not sure how they would align with the existing pulleys on the engine.

Or ....AM I OVER THINKING THIS ISSUE?
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Old 06-05-2020, 04:38   #2
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Re: Alternator

Take it off and go to an alternator shop. Ask for an estimate for the repair, you may be in for a surprise.
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Old 06-05-2020, 21:44   #3
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Re: Alternator

Was it coolant or seawater than drowned your alternator? If seawater immediately take it off & submerge in freshwater. Guess it was seawater going by the quantity. Change water a few times, leave overnite & then saturate with WD40 or similar then dry & take sailormeds advice.
If you are very lucky it may only be the voltage regulator thats fried but I'm just guessing as I'm not an electrical expert.
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Old 07-05-2020, 12:06   #4
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Re: Alternator

Well! I'm never that lucky! I took it to an alternator shop that's owned and run by a sailor! He tried to open it up and all the bolts broke when he tried to turn them! When he finally got it open, it was too far gone to repair. It basically crumbled. So I'm thinking it failed because of old age and the salt water bath was just shined a light on the failures. Got a new one and it's already installed!
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Old 07-05-2020, 14:12   #5
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Re: Alternator

Quote:
Originally Posted by dennismenace111 View Post
Well! I'm never that lucky! I took it to an alternator shop that's owned and run by a sailor! He tried to open it up and all the bolts broke when he tried to turn them! When he finally got it open, it was too far gone to repair. It basically crumbled. So I'm thinking it failed because of old age and the salt water bath was just shined a light on the failures. Got a new one and it's already installed!
You didn't muck around! Can you tell us what you bought & details? I believe we have the same alternator on our Yanmar ysm8 & have no interest ( or enough $$$$ ) in buying a genuine one off a Yanmar dealer if we need a replacement.
Aren't using the Hitachi at present as we have a 55 amp Bosch alternator as well & find the Hitachi too slow but need it for backup.
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Old 07-05-2020, 17:08   #6
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Re: Alternator

My local Sailor/Alternator shop owner got me this one for $100 U.S. Installed it this morning and it fits perfectly. Took all of 30 minutes to install and most of that was trying to get that bottom bolt started and turning in the right direction... and losing it in the bilge for a bit. I had him take the pulley from my old alternator, clean it up, paint it and put in on the new alternator... I was afraid the pulley would be different and Id end up with an engine cave full of black dust. The PO of the boat used some really cheap belts as it took me weeks to get it clean.

This is a link to the same alternator that I bought.. but I didnt get it from this site.. I bought it locally. Do a google search on 021903640I. It shows as compatable with the Hitachi LR155R alternator.

https://www.obbstartersandalternator...25-p-4339.html
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Old 07-05-2020, 17:22   #7
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Re: Alternator

Thanks a lot for the info.
I mucked it up anyway as the ysm8's alternator is an LR 135 i.e. only a 35 amp alternator but your post will help someone else I'm sure as i suspect there are a lot more 2GM20's than ys8's around.
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Old 07-05-2020, 17:34   #8
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Re: Alternator

My friend wanted me to put in an 80 amp alternator but it was a bit more and I didn't see a need for it! I've got two battery banks of two 12v wet cell batteries and not alot of 12v power hungry equipment. I just didn't really see a need to spend the extra bucks.
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Old 07-05-2020, 19:44   #9
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Re: Alternator

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Originally Posted by dennismenace111 View Post
My friend wanted me to put in an 80 amp alternator but it was a bit more and I didn't see a need for it! I've got two battery banks of two 12v wet cell batteries and not alot of 12v power hungry equipment. I just didn't really see a need to spend the extra bucks.
Well I think you made the right decision. They draw quite a bit of power from the motor, we actually cant use our 55 amp alternator whilst driving the boat with the motor only with our 8hp engine when the battery voltage is low, it makes the engine blow black smoke i.e over-fuelling. Thats even tho the most I can get out of the alternator is 35 amps at 3000 engine rpm when the alternator is cold. We are over-propped drastically as well which contributes to the over-fuelling problem. I was thinking of putting an 80 amp alternator on & de-rating it so it didnt get hot but the 55amp alternator only gets to 70oC anyway under full load so thought it was unnecessary.
Of course you have an extra 12hp so not so handicapped but just a warning about power draw from an alternator
We have an Engel fridge running 24/7 but solar usually keeps the batteries full, we only use the Yanmar for charging when it's too cloudy/raining.
Be interesting to see how your $100 alternator pans out. If made in Taiwan in a japanese joint venture factory could be a winner but if PRC origin it will be a lucky dip. The Hitachi alternators have a thermal cutout which stops them from cooking themselves. Good idea but makes for slow charging which is why we moved to the Bosch 55amp for charging at anchor.
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Old 07-05-2020, 23:06   #10
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Re: Alternator

The amp ratings for alternators are only for a short time the design assumption being that a single cranking battery will recover voltage fairly quickly and the regulator consequently wind the amp output of the alternator back fairly quickly.

A problem occurs when we put them to charging hundreds of amp hours of house batteries and the voltage does not rise fairly quickly. Unless the alternator is fitted with temperature sensing which winds back the output when the alternator gets to hot the extended period producing high amps will start to produce to much heat and cook the alternator.

An oversized alternator is generally more forgiving of this treatment.
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Old 08-05-2020, 14:17   #11
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Re: Alternator

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Originally Posted by RaymondR View Post
The amp ratings for alternators are only for a short time the design assumption being that a single cranking battery will recover voltage fairly quickly and the regulator consequently wind the amp output of the alternator back fairly quickly.

A problem occurs when we put them to charging hundreds of amp hours of house batteries and the voltage does not rise fairly quickly. Unless the alternator is fitted with temperature sensing which winds back the output when the alternator gets to hot the extended period producing high amps will start to produce to much heat and cook the alternator.

An oversized alternator is generally more forgiving of this treatment.
Thanks for the info,
.Apologies for the thread drift but is 35 amps all I can expect out of our 55 amp alternator? This is all I can get trying to charge a pair of 6v 225amp deep cycle batteries in series which were down to 12.1 v before charging started. Alternator cold & alternator rpm probably 6000.
Batteries are very old & were a giveaway that I resuscitated if that has any bearing on it. Alternator was rebuilt & tested according to alternator bible instructions. I.e dodes & windings checked, VR & bearings replaced by me a complete electrical novice.
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Old 08-05-2020, 17:18   #12
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Re: Alternator

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Originally Posted by Compass790 View Post
Thanks for the info,
.Apologies for the thread drift but is 35 amps all I can expect out of our 55 amp alternator? This is all I can get trying to charge a pair of 6v 225amp deep cycle batteries in series which were down to 12.1 v before charging started. Alternator cold & alternator rpm probably 6000.
Batteries are very old & were a giveaway that I resuscitated if that has any bearing on it. Alternator was rebuilt & tested according to alternator bible instructions. I.e dodes & windings checked, VR & bearings replaced by me a complete electrical novice.
You were probably lucky to get 35 amps!!!!
Your batteries would have been the choke point, highly unlikely they would have accepted more amps even if you had a 100 amp alternator.

Simply put, the maximum charge accepted by a battery is totally dependant on the battery chemistry at the time of charging. The only time the alternator limits the current is when the rated alternator current is less than the battery acceptance charge. Your old batteries couldn't accept more because their chemistry wouldn't allow it. Said another way, they are knackered!

If you had turned on say a 120W load (i.e. a 10 amp, 12 volt spotlight etc), your alternator would have most likely delivered 45 amps i.e. 35 amps to the battery and 10 amps to the light. Try it and see!
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Old 08-05-2020, 17:43   #13
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Re: Alternator

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Originally Posted by Wotname View Post
You were probably lucky to get 35 amps!!!!
Your batteries would have been the choke point, highly unlikely they would have accepted more amps even if you had a 100 amp alternator.

Simply put, the maximum charge accepted by a battery is totally dependant on the battery chemistry at the time of charging. The only time the alternator limits the current is when the rated alternator current is less than the battery acceptance charge. Your old batteries couldn't accept more because their chemistry wouldn't allow it. Said another way, they are knackered!

If you had turned on say a 120W load (i.e. a 10 amp, 12 volt spotlight etc), your alternator would have most likely delivered 45 amps i.e. 35 amps to the battery and 10 amps to the light. Try it and see!
Na Wottie it doesn't!
When fridge comes on whilst alternator putting out 28amps @ 1600 engine rpm, our usual at anchor charge rpm ( fridge draws 8 amps roughly but dependent on battery voltage ) alternator output does not change.
Although my knowledge of electrickery is minimal it occured to me to check that or perhaps
Thanks for the lesson about state of battery affecting alternator output. Can I work that backwards? i.e. seeing how the batteries do accept 35 amps does that suggest they are not totally knackered? Or am I making a link that isn't there?The hydrometer says they are ok when charged & they seem to be good enough for our 50-60 amp over 24 hr needs & start the engine no problem. Or does it suggest an alternator fault? bearing in mind I can't remember trying fridge on at max revs just at anchor charging revs. Tho I probably did try that, I just can't remember
I did realise the battery state does have some effect as after about 90 mins charging at anchor from a 12.1 or 12.2v start the amps from the alternator are down to 20 even tho the volts are only 14.5 & VR is a 14.8 one.
Feel free to school me up some more if you aren't on the 2qm20 mission
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Old 08-05-2020, 18:11   #14
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Re: Alternator

Besides alternator temperature another limitation is the vee belt running over the necessarily small alternator pulley needed to keep the alternator speed up at an engine fast idle to a place where the alternator can generate both the amps and enough airflow with its fan(s) to keep itself cool. If you can long term get more than 50 or 75 amps with a 1/2" belt without belt dusting or without coolant pump bearing failure from over tightening the belt, more power to you.

Google away on vee belt size vs horsepower remembering that the horsepower load from the alternator is volts times amps to give you electrical watts. Electrical watts divided by efficiency (80% ?) is mechanical watts. Mechanical watts divided by 746 is mechanical horsepower. There is a reason that serpentine belts are used on modern cars and are often spoken well of here.

Bill
who just replaced his coolant pump when its bearings failed.
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Old 08-05-2020, 23:10   #15
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Re: Alternator

Another factor is the wiring between the alternator and the battery on charge and whether or not your regulator has a voltage sensing terminal connected to the battery terminal.
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