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Beta Marine Repower Solutions -> Beta Marine Engines -> Replace 3GM20 with Beta 38 in Seidelmann 37
Post Info TOPIC: Replace 3GM20 with Beta 38 in Seidelmann 37
KeyWestPirate


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Replace 3GM20 with Beta 38 in Seidelmann 37
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Would it be possible to replace the existing Yanmar 3GM20 with a Beta 38 in my 1983 Seidelmann 37?

My purpose is thus: 

I'd  like to add the optional pto to drive a watermaker pump,  and a larger alternator driven by a poly V belt.   I would purposely like to cruise a little lower on the power curve, say 2200-2400 RPM.  I understand that the boat might have to be re-propped.

The boat currently has AC and I would like to add 12VDC refirgeration and a decent inverter/charger, say 2500 watts.  The AC currently draws 500 watts plus another 70 for the pump.  I'm not trying to cool the entire boat, just the double berth forward for sleeping comfort and security at anchor.

The engine would operate in two modes under my plan:  Powering the boat through the water, plus making water and any electrical power I need;  and running at anchor driving the watermaker pump and alternator during extended stays at anchor.

With the space and weight I save by not having a Genset I can add some AGM's to abosrb the higher alternator output.  I've been down the other road with a 7.5KW NL genset, a 600GPD watermaker and 30K BTU plus in a 40 foot Beneteau, and it was OK, but the Genset was one more machine to manage and maintain.  And I didn't need anything like that much water or power. 

Is this a viable plan?  Has anyone else attempted it?  What would I give up in fuel economy?  How complex will the changeover be?  Am I missing anything?

What's the vibration like on the Beta 38 at say 1000?  Will I feel it forward?

Thanks!

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Stanley


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This is actually becoming more common but I think that you need to consult someone who specialises in electrical systems. You need to size the inverter correctly or you will not be able to use your AC appliances. All the batteries that you will need to make this work will add to the weight of the boat and will also take away from your storage.

We can supply the Beta 38 with a 100 amp alternator in the standard position and a 2nd alternator which will give you 175 amps. Both of these alternators will be driven by poly vee belts. Naturally this will require a very large battery bank so that you you can get the benefit of the large alternators. You will need to use a bilge blower to get the heat away from the alternators to keep the output up. Expect to run the engine at about 1400 to 1800 when demanding high output from the alternators.

The Beta 38 is much more power that your boat needs but the engine will still have to be propped so that it can reach its max RPM in gear under power. This is actually a very smooth running and quiet engine and you will be pleasantly surprised at how little noise and vibration it makes at any speed.

Regards, Stanley

     



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KeyWestPirate


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Thanks, Stanley for the fast response.

I completely re-wired my Beneteau and converted it to 24 V in the process (probably a mistake because of the extra cost and difficulty in obtaining 24V electrical items).  I had a 4KW Xantrex and 1000AH @24 Volt of Gel Cels in the port ****pit locker.  High and dry, but I always worried the boat wouldn't right itself.  The Genset was on the starboard side.  It was balanced side to side but I had to add 600 lbs of lead to the bow, this after I put in bow thrusters and another couple of Gelcels up front to drive the bow thrusters and windlass.

It all worked great, but it was too much, too much weight, too much power, overdone.  It was a tub.  My wife loved it.

I guess the thrust of my question is, will the 38 fit the space of the 3GM20 on the Seidelmann 37?  I can't find specs for this legacy Yanmar online.  Have you had personal experience with a 3GM20 upgrade to a  Beta38?

I saw one of your engines on a boat in Cuba, it had a larger alternator and a watermaker pump running off the engine.  The owner was very pleased with the solutions he had found for power and water.

Thanks again, John

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Stanley


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Hello John,

The Beta 38 is a larger engine that the 3GM and you must expect to have to make changes to your engine compartment.  Here is a link to the drawing of the Beta 38 and I suggest that you check this against your measurements of your 3GM http://www.betamarinenc.com/BV1505-PRM120-65AMP.pdf 
The Beta 28 is very similar in size to the 3GM and is also a 3 cylinder engine. The 38 is a 4 cylinder and is longer. The 3GM was supplied on 14.5" mount centers (port to stbd) and the Beta 38 is supplied with 16.14" mount centers. We can provide 14.5" mounts if your engine beds wont accept the larger mount width.

Check you transmission as your engine may have the 7 degree down angle transmission. We can also supply this.

Regards, Stanley 

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KeyWestPirate


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Thanks again,  Stanley.

The 28 would be the conservative and easy re-power, and may ultimately make the best sense for my situation.  I'm a "More Power" kind of guy . . sometimes this is not the best solution.

Putting the difference into some solar and wind generation might be wiser.

I believe the 3GM20 was rated at 18HP (this is a 1983 engine, original and still running OK), so the 28 will give me a modest HP increase. 

If I get the optional 100 AMP alternator and use a smaller watermaker pump (2 or 3HP ) running off the PTO, what do you estimate my RPM would need to be to generate that much continuous power?  With inverter loss I'll need 800 watts for the AC (although the AC will cycle so that won't be a continuous need). 
Can I get that from the 100 AMP alternator and a smart regulator?

What DO you allow attached to the pto pulley in terms of load?

Thank you very much for your time and advice.

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Stanley


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Side load from a forward PTO should not exceed 15% of rated output so 2 to 3 HP pump for a watermaker is fine.

I have attached a document that shows the output of the 100 amp alternator on the Beta 28 to 38.

Your boat is actually quite light and has a very easily driven hull so an extra 10HP will be a great boost.

Stanley



-- Edited by Stanley on Wednesday 29th of July 2009 07:50:47 AM

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