Engine Pully's

trlrtrsh · #1 10-04-2011

I need to upgrade the pully's on my Diesel engine to one"s that accept a 1/"2 belt. Identification on the engine is kinda sketchy, but I do have the shop manual. That say's it's a BMC 2.52 litre 154 cu in. inline 4 cylinder. The manual also refers to it as a Yachtsman Diesel engine. It's a 50hp model.
The reason for changing from 3/8" pully's to 1/2" pully's is to accomodate a 120 amp generator.
If any of this makes sense to anyone, I'd appreciate any input.

celenoglu · #2 10-05-2011

A second "pully" same size of your engine's is more reasonable, you will use two belts which will transfer more power than a single thicker belt.

BELLATRIX1965 · #3 10-05-2011

Quote:

Originally Posted by celenoglu

A second "pully" same size of your engine's is more reasonable, you will use two belts which will transfer more power than a single thicker belt.

I agree with celenoglu - multiple smaller vee belts (read two) would be better than one large vee belt. Any chance there is an on-line forum for your boat manufacturer that could help you I.D. your engine?

Liquorice · #4 10-07-2011

You might already be aware of this, but as an ex-Brit, when I see BMC, my first thought is "British Motor Corporation".
I'd start searching in that area or on UK yachting forums.
sam :-)

trlrtrsh · #5 10-07-2011

Thanks for the input so far. Liquorice, yeah the Name BMC also made me think of British Motor Company, also the apearance reminds me of the British Lehman engines of old.
celenoglu and Bellatrix1965 changing to a dual pully system is a good suggestion, but it doubles my pully problems for right now. I would have to change the crank/waterpump/and the Alternator pully.
The engine is in a Yorktown39CC, and was built by the Yorktown factory in Long Beach California. They also sold owner completed boats, but this one was a sailaway boat. It sold in 1980.
I Appologize for not listing the boat in my original message. The other thing I would prefer a single pully over a dual is the clearance of the forward bulkhead, it's very tight right now. The engine room is quite large, but the access to the front of the engine is real tight, and you have to be a contortionist to service the front of the engine.
I know someone is going to suggest repower but this engine runs smooth, fairly quiet, doesn't smoke after a warm up, and has very low hours for such a old engine. (All that and I'm a tightwad).
According to the owners manual, the engine was sold by a company in Long Beach Calif. and I tried to call them, but all I get is a busy signal. I think I will try to do an online search for the company.
Again, thanks for your thoughts, If anyone has any ideas, I would appreciate it.

mikefossl · #6 10-07-2011

It might be worth a shot to see if there is a serpentine kit that would fit. Contact electromaax. I have a Westerbeke 44a and just upgraded to multi-v pulleys and belt to go with a 160 amp alternator.

BELLATRIX1965 · #7 10-08-2011

Quote:

Originally Posted by mikefossl

It might be worth a shot to see if there is a serpentine kit that would fit. Contact electromaax. I have a Westerbeke 44a and just upgraded to multi-v pulleys and belt to go with a 160 amp alternator.

mikefossl said what I was about to suggest - a serpentine belt kit would solve your problem in about the same space. Chances are you are going to wind up renewing all the pulleys regardless. Trans Atlantic Diesel sells a serpentine belt kit for Perkins/Westerbeke engines - they could probably hook you up with one for your engine, given enough information.

www.tad123.com

fcsob · #8 10-09-2011

How proud is the 1/2 inch belt on your pulleys?

hellosailor · #9 10-09-2011

Trash, I'd vote against twin belts. With twin belts there's a continuous problem because one belt always carries more load than the other, they get unbalanced and you wind up going through lots of belts. This is one reason the auto industry went to serpentine belts to replace the dual-belt applications for police and taxi use.

Odds are that you will need to go to a machine shop and have two pulleys fabricated. Depending on your local market, what metal they have on hand or you want to use, that pulley could cost you a couple of hundred bucks but it is a simple lathe turning job that any machine shop can do.

There ARE many different v-belt profiles, "a half inch" is meaningless. If you are buying an alternator with a specific pulley already on it, find out what the belt profile is and make sure the new flywheel is made with the same profile.

While you're at it, check the pulley diameters to make sure you'll be turning the new alternator at the optimum speed for your use, and within the speed range it is rated for. Won't cost ay more, will ensure better charging system.

Stu Jackson · #10 10-09-2011

I'm running a 3/8" belt with a 100A alternator. Works just fine although sometimes I used the Small Engine Mode when the house bank is down towards 50%. See: Alternator Output Management with External Regulators [Small Engine Mode]

A lot depends on how big your house bank is and how high a real load you'll see on your alternator based on battery acceptance. Our house bank is 390 ah.

Works for us.