Got Questions? Ask Them Here.

Sep 25, 2008
957
Macgregor & Island Packet VENTURE 25 & IP-38 NORTH EAST, MD
Maine, I just installed a PSS shaft seal and after reading your "how to", I installed a Taco Hy-vent at the end of my vent line. Its a nice, clean way to finish the vent line off. One silly question though, the threaded cap on the top of the vent, what do you do with that? tighten it up or leave it loose? If its loose, what keeps it from vibrating off? or isn't the cap really needed? Thanks for your help and informative "how to's".
???
 
Feb 14, 2014
7,399
Hunter 430 Waveland, MS
Ask away!
I have been doing a galvanic corrosion survey on my boat about every 3 months with my Ag/AgCl reference probe. Great peace of mind.
But...
My most recent survey showed my shaft zincs at -640mV about 3 months after my new zinc were installed.:yikes:
(at new install time -840mV verified:thumbup:)
Trying not to panic, I quickly hooked up my drop zinc and it went to -680mV o_O.
It took me about an hour to figure the recent huge rain fall had dropped the salinity of our inland marina.
I was shocked to see that huge difference. I went out to open salty Gulf waters and got -820mV with shaft zinc :).
After diligent web search, I found no adjustment to the standard Ag/AgCl table based on salinity or temperature.

Do you have or know of such a compensation formula or table?

I would seem obvious/simple ( 820 - 640 = 180 mV difference in the electrical conductivity of water based on salinity).
But no joy in Mudville.... Hopefully you are better than Casey at the bat!
Jim...
 
Feb 14, 2014
7,399
Hunter 430 Waveland, MS
Here is the back side wiring diagram for my batter switches. I just noted the Com line for Starter Battery Isolator.

My guess is it acts to isolate the genset alternator from engine alternator.
What is it? What would it look like, 1997 vintage? Where might it be located?
Jim...
ElectBackDiag.jpg
 
Mar 28, 2014
49
Catalina 30 Hyde Park NY
.I have a Catalina 30TR, set up with a staring (deep cycle) battery and house connected in parallel two (deep cycle) batteries. I also have been given a same size (Gp27) battery, it shows on test to not have the same capacity as the two others.
If I add this battery to the house bank and connect the charging cables across the whole bank (outside + and -) will I,
1, Decrease or increase the overall capacity?
2, Have the charger "overcharge the bank" by it recognizing "low" one by trying to bring it up.

Appreciate the help, not only for these questions but all the help you have given us all in the past.
 

Gene S

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Nov 29, 2015
181
Delphia 37 Tacoma
I have a question about an inverter recommendation. My boat has 3 gp24 batteries in paralell, no start battery. I am planning to go to 3 gp31 as I have the room. I dont use much electricity but I would like to power the 115 system and heat the quick boiler that has a 1200 watt heating element instead of using the engine. What inverter would you recommend? Also solar is in the near future. Thanks in advance for all the help you give all of us.
 
Sep 28, 2008
922
Canadian Sailcraft CS27 Victoria B.C.
A 1200 watt AC element requires about 120 amps from your batteries. Your battery bank will be effectively dead (50% SOC) in an hour or less.

Inverters can make sense for using some items - microwave for a few minutes for example. But water heaters or air heaters should not be run with an inverter in most cases.
 

Gene S

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Nov 29, 2015
181
Delphia 37 Tacoma
A 1200 watt AC element requires about 120 amps from your batteries. Your battery bank will be effectively dead (50% SOC) in an hour or less.

Inverters can make sense for using some items - microwave for a few minutes for example. But water heaters or air heaters should not be run with an inverter in most cases.
Good to know. But why do they sell high wattage inverters? What kind of battery bank do you need to run say a 2k watt inverter?
 
May 17, 2004
5,028
Beneteau Oceanis 37 Havre de Grace
A microwave might draw 1500 watts, so that's an example of a reason to have a high wattage inverter. But in 5 minutes of use at 1500W you'll only draw about 11Ah, which is much more manageable than the 100Ah you'd draw in the hour you'd run the water heater.
 
May 17, 2004
5,028
Beneteau Oceanis 37 Havre de Grace
By the way, here's the math we're using to figure out the draw -

Amps required is watts divided by 12 volts

Amp hours is the number of amps being drawn times the number of hours drawn for.

A typical group 31 battery probably has about 100-110 amp hours of capacity, but you don't want to use more than 50% of that or you'll significantly shorten your battery life. That capacity is also very approximate as it varies based on things like the rate of draw and battery health.
 
Sep 28, 2008
922
Canadian Sailcraft CS27 Victoria B.C.
Good to know. But why do they sell high wattage inverters? What kind of battery bank do you need to run say a 2k watt inverter?
Many cruisers have a battery bank composed of four 6 volt golf cart batteries for a total of 440 - 480 AH @ 12 volts. This allows running a 2000 watt inverter for items such as a microwave. But as posted it only runs for a few minutes.

A fairly large bank is required to run a 2000 watt inverter at or near its maximum output as well because a smaller bank will have too much voltage drop when the load is large - this causes the inverter to shut down from too low a voltage.

I know of only one person who uses his inverter to make hot water. But he has 800 AH of LiFePo4 batteries and 1500 watts of solar panels - definitely a unique situation.
 

Gene S

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Nov 29, 2015
181
Delphia 37 Tacoma
Ok, tnx for the info. Right now I get the hw from the engine coolant. It stays warm overnight and I run the engine for about 15 min to reheat it and put some charge into the batteries. I need to see how long the heater runs from dead cold and from overnight reheat. As is I'm alone and I take navy showers anyway. I'll see if I can borrow a clamp on ammeter from my neighbor and see the actual current draw.
 
Feb 6, 1998
11,665
Canadian Sailcraft 36T Casco Bay, ME
I have a question about an inverter recommendation. My boat has 3 gp24 batteries in paralell, no start battery. I am planning to go to 3 gp31 as I have the room. I dont use much electricity but I would like to power the 115 system and heat the quick boiler that has a 1200 watt heating element instead of using the engine. What inverter would you recommend? Also solar is in the near future. Thanks in advance for all the help you give all of us.
Running a water heater off 3 G-31's is bad idea.

Three G-31 batteries will only give you about 300Ah's with only 150Ah's usable to 50% SOC from 100% SOC. When out cruising you will only really have about 90Ah's of actual usable capacity or from about 50% SOC to about 80% SOC. Now stack voltage sag, Peukert and inverter inefficiency of about 15% on top of all this and your usable capacity is very, very small.

Large inverters are sold for massive banks or for very short duration use such as 30 seconds of microwave.

1200W / 11.5V = 104.35 X 1.15 = 120A (Note: voltage will not remain steady and as it drops the amperage draw from the inverter increases)

Assuming a Peukert of a typical G-31 flooded battery of about 1.27 this means that at 120A the bank is really only 171Ah's, not 300Ah's, and the Peukert corrected amp load of 120A becomes 210A with the Peukert correction....

If you want to heat water with your batteries it is going to get expensive, very, very expensive in regards to alternator, regulator, pulleys, battery bank cabling etc. etc. etc.......
 

Gene S

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Nov 29, 2015
181
Delphia 37 Tacoma
Ok, the consensus is in. Bad idea. Good to know before I waste money. Just got off a week cruise where I worked on timing when I do things like showering after motoring and dropping anchor and after putting some charge in the batteries in the morning. Thx Main and the others for the education.
 
May 7, 2011
281
C - 30 # 3573 Lake NormanNC formerly Bflo NY
Hx Anode and Bonding

Rod, question on Hx corrosion. You note on your site how many dissimilar metals a Hx can contain.

In fresh water should the Hx anode be Aluminum, like the others?
What about bonding -- I thought it would need to be bonded for the anode to do any good, but have read that it still protects the Hx (i.e., the local "cell" created by its dissimilar metals.)

So, what's the recommendation? Bob or not to bond, and is there any pro/con one way or the other choice?
Seakamp doesn't seem to have a real recommendation on this -- leaves it to the owner (blindly) to decide -- i.e., without disclosing the pros or cons and letting us decide with real information.

"we have been asked this many times . is always best to be in contacted with engine when possible On generators we have a ground stud on our heat exchangers and does seem to extend life I have came to a point to let the customer do what they see best. Seems no one has ever pinned down the electrolysis issues . there are all kinds of publications on it and they all have their own opinion. give me a call if you want to discuss further"

'electrolysis' -- Arrrrrrrrgh!!
Just shows you, just cuz you do it for a living doesn't mean you know which end is up.

Thanks,
Ken K
 
Jun 25, 2004
1,108
Corsair F24 Mk1 003 San Francisco Bay, CA
Ask away!
I'm buying a 1993 Corsair with a through hull 1" above the static waterline that lacks a valve. When heeled, the through hull is below the waterline.

I'm thinking of using Marelon fittings. Forespar has documentation which states the following:
"THE FORESPAR MARELON BALL VALVES AND THRU-HULL FITTINGS MEET AND EXCEED THE ABYC H-27 AND ISO 9093-2 STANDARDS AS PRESENTLY WRITTEN IN ALL RESPECTS."
(see http://www.forespar.com/pdf/techTips/M10-Marelon-Marine-Grade-Plumbing-Systems-with-certificates.pdf)

Marelon Series 93 ball valve (forespar part number 905101) has no flange. See pic below. Would it be okay to use it backing plate and with reinforced hose? Would that meet ABYC H27 standards for the 500 pound load?


Would it be better to use Forespar part 931153 (below) with a backing plate? It's much more compact than the 905101, and has a small flange. I'd rather not drill extra holes in the hull for through bolts.

Or must I use something like this:


Thank you very much in advance.
 
Feb 6, 1998
11,665
Canadian Sailcraft 36T Casco Bay, ME
I'm buying a 1993 Corsair with a through hull 1" above the static waterline that lacks a valve. When heeled, the through hull is below the waterline.

I'm thinking of using Marelon fittings. Forespar has documentation which states the following:
"THE FORESPAR MARELON BALL VALVES AND THRU-HULL FITTINGS MEET AND EXCEED THE ABYC H-27 AND ISO 9093-2 STANDARDS AS PRESENTLY WRITTEN IN ALL RESPECTS."
(see http://www.forespar.com/pdf/techTips/M10-Marelon-Marine-Grade-Plumbing-Systems-with-certificates.pdf)

Marelon Series 93 ball valve (forespar part number 905101) has no flange. See pic below. Would it be okay to use it backing plate and with reinforced hose? Would that meet ABYC H27 standards for the 500 pound load?


Would it be better to use Forespar part 931153 (below) with a backing plate? It's much more compact than the 905101, and has a small flange. I'd rather not drill extra holes in the hull for through bolts.

Or must I use something like this:


Thank you very much in advance.
The only product in those images that meets the ABYC strength requirements, for your size, is the middle one (93/OEM Series). The top and bottom models fail well below the ABYC requirement..
 
Feb 2, 2006
464
Hunter Legend 35 Kingston
Question: What is forming this layer on my Gori prop?

20161211_114423.jpg 20161211_114406.jpg
I can scrape it off with a piece of hard plastic. It is immune to vinegar, CLR, acetone, paint stripper, and denatured alcohol. As you can see, once scraped off, the finish is bright and shinny. I'm in fresh water, and have magnesium anodes on my stainless shaft. The spotty appearance in the "unscraped" area is due to some light marine growth that I washed off after haulout (can't remember if the growth was on the bare metal spots, or where the "layer of stuff" is. Once scraped, the surface is smooth (no pitting or difference in surface height).

Any idea on what this is? And what might make it easier to remove?
Chris