I'm looking for some other sailors who have High-Output Alternators on small Diesels (Yanmar SB8, for example). What I am searching for is the real world experience of whether you use a high-output alternator on a small HP (8 HP) diesel, and if that experience is a happy one? I've heard stories about water pumps shafts being sheared and warnings about excessive loading causing crankshaft problems, and reduced prop shaft power due to excessive loading caused by a high-output alternator (125 AH vs "stock" 35 AH). There are other stories abot people using a by=pass switch to reduce the field to the alternator, so the loading can be minimized when shaft output power is more important or delayed while starting. Please bear in mind when I say "stories", I mean sailors describing their experiences. I have looked at the Yanmar GM series as well as the SB series, and I fail to see what adverse connection there is between the alternator and the water pump, except for a parallel flange on the pulley on the crank shaft pulley? I need to redo my entire DC charging capability, and although have several excellent resources, I still sense some disparity between using a High output alternator with its corresponding load. According the Balmar web site, it takes approximately 1 HP to produce 25 AH of alternator current. At the theoretical "fill load" of a 125 AH alternator, that's about 5 hp out a practical 7 hp Yanmar SB8 diesel. Thoughts, opinions, facts, experience?
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Marc Honey
HP Loss
Main thing I remember is that a high output alternator on a small diesel (8-16hp) will suck about 3-5hp from it... can you afford that?
Main thing I remember is that a high output alternator on a small diesel (8-16hp) will suck about 3-5hp from it... can you afford that?
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Jack
Watts and HP
There are 746 watts in a hp and 14 X 125 or 1750 watts needed with 100% efficiency. This would be about 2.3 hp in an ideal world. This world isn't soooo, 3 to 4 hp would be a good guess.
There are 746 watts in a hp and 14 X 125 or 1750 watts needed with 100% efficiency. This would be about 2.3 hp in an ideal world. This world isn't soooo, 3 to 4 hp would be a good guess.
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andy
8-5=3 I think you need more hp
I have a 3gm30F with 125 amp alternator. There is a noticable loss of hp when on full charge. I have a kill switch in the field lead wire just in case I need the extra power. Starting the motor under full alternator load caused hard starting until I installed a Balmar regulator with a delay start feature. The Balmar also has an option to reduce the load with an external switch. Your engine is rated at 8 peak horse power at 3400 (?) rpm. At anything less you will just be making enough power for the alternator and getting up to that rpm under prop load will be very difficult.
I have a 3gm30F with 125 amp alternator. There is a noticable loss of hp when on full charge. I have a kill switch in the field lead wire just in case I need the extra power. Starting the motor under full alternator load caused hard starting until I installed a Balmar regulator with a delay start feature. The Balmar also has an option to reduce the load with an external switch. Your engine is rated at 8 peak horse power at 3400 (?) rpm. At anything less you will just be making enough power for the alternator and getting up to that rpm under prop load will be very difficult.
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Peter Brennan
Juice takes power
I used to have a Yanmar YSE8 in a Dawson 26. It put out just enough power at full throttle to drive the boat at 5 knots. Seems to me you can either charge batteries or run the boat, not both, if you install a high-ouput alternator. Even then, the loading on the pulleys and belts will not be negligible and could well damage the engine because you will be putting excessive side thrust on shafts and bearings, for which it is not designed. Our present boat has a Universal 32 HP with high-put alternator and separate elctronic regulator that does not kick in until the engine is up to speed. When it does kick in to charge depleted batteries at 125 amps or thereabouts, the engine starts lugging very noticeably. The alternator at full output really puts a load on the engine.
I used to have a Yanmar YSE8 in a Dawson 26. It put out just enough power at full throttle to drive the boat at 5 knots. Seems to me you can either charge batteries or run the boat, not both, if you install a high-ouput alternator. Even then, the loading on the pulleys and belts will not be negligible and could well damage the engine because you will be putting excessive side thrust on shafts and bearings, for which it is not designed. Our present boat has a Universal 32 HP with high-put alternator and separate elctronic regulator that does not kick in until the engine is up to speed. When it does kick in to charge depleted batteries at 125 amps or thereabouts, the engine starts lugging very noticeably. The alternator at full output really puts a load on the engine.
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Pete Albright
ZRD.Com Balmar Information
Check out the link for http://www.zrd.com/esd-index.html. This is a site recommended by Balmar. They have some good information on loading and belt and pully selection.
Check out the link for http://www.zrd.com/esd-index.html. This is a site recommended by Balmar. They have some good information on loading and belt and pully selection.
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Don Alexander
Cruel Man
Loyal little diesel slogging its heart out to push the boat along - be kind to it. How about a new regulator on the existing alternator? There are retrofit ones which will keep the alternator on full charge until the batteries are okay without sapping the engine output. One make is Adverc but there are plenty of others. Regards,
Loyal little diesel slogging its heart out to push the boat along - be kind to it. How about a new regulator on the existing alternator? There are retrofit ones which will keep the alternator on full charge until the batteries are okay without sapping the engine output. One make is Adverc but there are plenty of others. Regards,
Not a total solution but have you considered....
Bob: This is not a total solution, but have you considered just upgrading to a Hitachi 55amp alternator. This would give you a nice boost without totally sapping your engine. They also make a 70amp unit too.
Bob: This is not a total solution, but have you considered just upgrading to a Hitachi 55amp alternator. This would give you a nice boost without totally sapping your engine. They also make a 70amp unit too.
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Ray Bowles
Main bearing wear is a major factor when using
high output alternators on small motors. For a motor of your size an alternator with an output above approx. 55 amps will put a strong side loading on your front main bearing regardless of where the water pump and alternator are placed unless driven directly off the front of the crank. Somewhere within the 360 degrees on the front of your motor the load will focus itself and eventually this will transfer to the rest of the bearings. This is only on old mechanics opinion, but he is a damn good mechanic! Ray
high output alternators on small motors. For a motor of your size an alternator with an output above approx. 55 amps will put a strong side loading on your front main bearing regardless of where the water pump and alternator are placed unless driven directly off the front of the crank. Somewhere within the 360 degrees on the front of your motor the load will focus itself and eventually this will transfer to the rest of the bearings. This is only on old mechanics opinion, but he is a damn good mechanic! Ray
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