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DonziNUTS
12-18-2014, 10:44 AM
Guru's,
I am starting my 1968 18' project and have a few questions about water cooling. First question is:
For Hp reason...should I look for a circulating pump for my 350 small block or a raw water pump? Should this be belt driven or crankshaft driven? I do have a crossover tube setup that I purchased cheap.
Second do I even need one due to having the pump in the Alpha drive lower unit pickup? Or do I need both?

Any guidance or convincing will be greatly appreciated!

Mike

Pat McPherson
12-18-2014, 12:30 PM
I would suggest running with a thermostat and circ pump with an Alpha drive just the way Merc sets them up. I would not rely on the raw water pump in the drive and a crossover to cool the engine properly.

You could add a crank or belt drive pump if you really want to run with the crossover but those will likely cost more than a circ pump. Either way, I would still suggest running with a thermostat.

gcarter
12-18-2014, 12:36 PM
An Alpha drive raw water pump doesn't really provide enough water to use a crossover, so a circulating pump is always recommended w/that drive.
I suppose the alpha impeller could be removed and a crank driven raw water pump could be added.
IMHO, the best way to make your engine happy is to add a transom pickup, and a crank driven raw water pump.
The Alpha impeller would be removed along w/the raw water connecting hose through the transom (the hole in the transom would be blocked off.

joseph m. hahnl
12-19-2014, 07:52 PM
I think Merc still uses that stock Alpha set up to this day. it was used in the pre Alphas also. so for at least 35 years and they haven't changed it. I think it would be a safe bet that you can say the system works. I'd wager there are more Alpha drives on earth using that setup then all other out drives combined. My answer is new Impellor and a stock belt driven circulator pump on the front of the engine. I have a Jabsco bronze raw water pump on my cruiser does the same exact thing as the raw water pump in my Alpha drive on the Minx. The difference is it cost about $700 for the Jabsco. That's a lot of beer and gas :biggrin.:

Pat McPherson
12-22-2014, 09:13 AM
I belive that the raw water pump and water flowing thru are required to keep an Alpha cool.
I have heard of people using the Alpha raw water pump to just cool the drive and use a pickup and other raw water pump to cool the engine. Sounds like extra stuff that would only be needed for a supercharged engine.
I know many guys that have run the standard Merc setup with 400HP+ stroker motors. Stock Alpha raw water pump and circ pump on the engine is the way I'd go.

DonziNUTS
12-22-2014, 09:25 AM
Thanks guys for the replies!! Still in the beginning stages so have some things to think about.

Thanks again!
Mike

woobs
12-22-2014, 09:33 AM
I used a marine alloy circulating pump on my Alpha/4.3 to keep the weight down. I couldn't justify any other performance benefits from moving away from a circulating pump with the Alpha.

My question now I'm building a SBF for the Ski Sporter would be... what about an electric circulating pump?

81202

ivypandas
12-22-2014, 01:15 PM
I'm not sure this will fit your application, but Amazon has a lightning deal sale (good for the next 2 hours) for a Jabsco pump. Supposedly it is a $460 list price but on sale for a short time for under $100, with free shipping:
http://www.amazon.com/dp/B000O8D1RC/ref=gb1h_tit_c-2_6282_130eb760?smid=ATVPDKIKX0DER&pf_rd_m=ATVPDKIKX0DER&pf_rd_t=701&pf_rd_s=center-new-2&pf_rd_r=0DTGBXTV1C1VCQTA2EX3&pf_rd_i=20&pf_rd_p=1980506282

BTW, I have no financial interest in this. I'm just highlighting a potential good deal for someone.

Davis

Conquistador_del_mar
12-22-2014, 01:46 PM
I'm not sure this will fit your application, but Amazon has a lightning deal sale (good for the next 2 hours) for a Jabsco pump. Supposedly it is a $460 list price but one sale for a short time for under $100, with free shipping:
http://www.amazon.com/dp/B000O8D1RC/ref=gb1h_tit_c-2_6282_130eb760?smid=ATVPDKIKX0DER&pf_rd_m=ATVPDKIKX0DER&pf_rd_t=701&pf_rd_s=center-new-2&pf_rd_r=0DTGBXTV1C1VCQTA2EX3&pf_rd_i=20&pf_rd_p=1980506282

BTW, I have no financial interest in this. I'm just highlighting a potential good deal for someone.

Davis

Thanks for the link! I just got one for a friend of mine whose pump was leaking (sounds like a personal problem - lol). Amazon charged sales tax, but still only $108.

DonziNUTS
12-22-2014, 03:59 PM
Thanks for the link but I missed the Lightning deal! Crap I would have gone that way.

ivypandas
12-22-2014, 05:00 PM
Thanks for the link but I missed the Lightning deal! Crap I would have gone that way.

Here is a different, better Jabsco pump (62 GPM versus the previous 14 GPM) that went on sale today at 8pm EST for $219.99:

http://www.amazon.com/gp/product/B000O8B56G/ref=gb1h_img_c-2_6282_0e3c804a?pf_rd_m=ATVPDKIKX0DER&pf_rd_t=701&pf_rd_s=center-new-2&pf_rd_r=14R67JNZKS2Y7ARQ8VN1&pf_rd_i=20&pf_rd_p=1980506282

Before the sale, it was priced at just over $337. The sale ends in about 3 1/2 hours so I hope you see it in time.

gcarter
12-22-2014, 09:55 PM
Here's a link to my personal favorite crank driven Johnson pump.
They're used on both SBC and BBC engines, and the good news......they're under $200. All the time.
I've used several from this supplier and no problems.

http://www.marineexhaustmanifolds.com/raw-water-pumps.htm