CNG & Sherwood Pump Dissection

[crieders]

I still have one of the old tanks which I have not refilled in a while. It has some rust spots on it and I wonder where to get a new tank and whether there are now more filling stations around

[Stu Jackson]

http://www.cngnow.com/stations/Pages/information.aspx

[KWKloeber]

Cliff,

The last time I investigated CNG availability, it wasn't looking good.  But call your local nat gas supplier and usually they can give you an idea of filling stations.

You can try calling Haun Welding Supply in Syracuse [315] 463-5241 -- Ask for Josh Haun.  They do propane tank inspections / certifications and might be able to help you with CNG or order a new tank.  They have a drop in Horseheads and Scranton or might do an empty tank via UPS.

Is your Hx in and operating??!?

Ken K

[Gary Brockman]

In Southern California, most of the fuel docks have CNG tanks where you trade your empty tank for a full one.

[crieders]

The heat exchanger works great, thanks to the excellent post on burping the baby
I am not crazy about 170° however even with a headwind when the water is below 50. I may just replace the Oberdorfer withthe Sherwood

[Stu Jackson]

The heat exchanger works great, thanks to the excellent post on burping the baby
I am not crazy about 170° however even with a headwind when the water is below 50. I may just replace the Oberdorfer withthe Sherwood

Cliff,

Glad it worked for you.

Don't do that!  The 170 is just a fine temperature.  It means you have a 160F thermostat and it's working just fine.  The only other thermostat is a 180F, which we have and the engine works just fine at 190-195F, has for many years.

The Sherwood is a rotten pump: too many parts.  Keep the Oberdorfer, it's a much better pump.

[KWKloeber]

The heat exchanger works great, thanks to the excellent post on burping the baby
I am not crazy about 170° however even with a headwind when the water is below 50. I may just replace the Oberdorfer withthe Sherwood

Cliff,

If you switch to the Sw G908 pump, it would be a giant step backward for you.  Especially since you are in salt water.

I've supplied seawater pumps for Universal and Westerbeke engines for 20 years, and if you are truly running warm, it IS NOT your brand (Ob) of pump, I guarantee that -- there's another issue besides the brand of pump.  I run 160 all year round with a 3/8" Ob pump, even on a warm lake when pushing the M25 to the max.

Compare the parts on a Sw pump versus the the Ob.   

Sherwood


Oberdorfer 202M-07 Pump (female shaft)


Oberdorfer 202M-15 Pump (male shaft)




Which makes more sense in a marine environment?  (and you should eliminate Ob p/n 4.)
http://www.c34.org/wiki/index.php?title=Why_do_some_of_our_engines_have_different_Oberdorfer_sea_water_pumps_than_others,_and_what_about_that_cir-clip_%22holding_the_impeller_on%22%3F

There's a dozen reasons for inaccurate temp readings at the gauge.

• Are you using the 160 F thermostat? Have you checked it to see at what temp it opens?
• Do your water heater hoses run to the coolant pump/thermostat housing, or are they in series with the your Hx?
• Still have the harness gummy bear plugs?
• Bad engine ground or bad ground (notorious) at the thermostat cap or sender threads.
• Do you have the OEM pump - i.e., 202M, or the newer N202M pump?   When did you have it serviced last?  The cover could be worn and the impeller not making good contact.
• A faulty temp sender. Check the resistance -- it should be 800-ohms at 72 F, and 55-ohms at 212 F.
• A faulty gauge.
• The temp could actually be running at 155 F.  The gauge and sender are accurate to +/- 15 degrees.  Check  the thermostat cap temp with a $20 laser thermometer.
• Is your charge voltage steady?  Above or below 14 v affects the accuracy of the temp reading.
• The sender is subject to self-heating (internal resistance raises the apparent temp of the coolant.)
• If you have the cast brass elbows, replace them with straight thru barbs for better flow  - yellow brass isn't approved for saltwater use anyway.
• Reduced cooling water path -- we had a C30 owner with a nearly blocked injection elbow - severely reducing the cooling flow.

• And on and so on.....

Also, unless you are persnickety about maintaining the engine and sea water pump, the Sw is the worst option of the two.  It's prone to the shaft seizing (the pump is IRON not bronze like the Ob,) and if it seizes, it can break the fork off the camshaft.  It's documented and it happens - to a couple owners that I know of.  If you live for regularly servicing a Sw pump rather than sailing -- and keep it operating like new --  then it's not a problem.  But, if it's sight-unseen, and a Ronco (set-it-and-forget-it,) then the Sw is not the best option.  Westerbeke blames the seizing problem on misuse -- and the factory Service Bulletin states that you MUST inspect "their" pump EVERY TIME you operate the engine (Bulletin 235-Update).  Yes, it's THEIR (Wb's) pump, the rights are owned by Westerbeke -- only Westerbeke can sell the G908 pump, and WB made sure it's the only one that fits the B-series engines, not because it's the best -- but because WB owns that pump and doesn't want a Ob pump installed.  It's the only pump that a Westerbeke/Universal dealer can legally sell for those engines, and can lose their dealership if they sell an Ob pump.  That's telling in itself that Wb has to force their dealers to sell that pump, 'eh?

Just last season a C-30er had to install an electric sea water pump (or pull the engine and pay for an engine job) after his Sw seized and sheared off his camshaft.

Here's what it can do (pic is a B series engine camshaft):



To prevent that, Wb had to provide reinforcing rings for the end of the camshaft (Bulletin 235,) and instruct owners to inspect the pump EVERY DAY.
EVERY DAY?  Really, Westerbeke?


Cliff, the above is a factual comparison not merely opinions of the two brands -- but it's YBYC as to which pump you feel is best suited for you.

Ken[/list]

P.S.  The only reason for running at a lower temp (160 - 170 F) is to avoid salt from precipitating out if in salt water, otherwise a diesel runs better at a higher temp like 190 F, and the higher temp thermostat should be used in fresh water. The Westerbeke high temp alarm switch, in fact, closes at about 205 F.

[Ron Hill]

Cliff : You didn't mention whether this 170 degrees engine temp is all of a sudden or id it's always been at 170 degrees??

[crieders]

This is very helpful
I don't know how to find out the answers to some of the questions but I will try to figure out
Prior to the new heat exchanger, I was running at over 190 in the heat of the summer....so we will see
I ran it for about 45 minutes on Sunday against a strong headwind in the cool waters of LI sound

[Stu Jackson]

Cliff, your engine knows absolutely nothing about "strong headwinds" regardless of where you are sailing.  All the engine and its cooling systems are "aware of" is the engine rpm and the ability of the HX/cooling system to remove the heat generated by the engine.

There have been numerous and repeated stories, for example, about how the old OEM 2 inch HX on M25 engines were insufficient for extended WOT operation.  When clean they'd work just fine.  Many of us replaced those 2" units with 3" models, making the engines just like the newer M25XP engines.

I can run all day at WOT without increasing my engine temperature.

Your Oberdorfer rw pump is just fine.  Listen to Ron's advice.  Keep track of your system temperature, establish a "baseline" and then go from there.

Good luck.

PS - Ken, I added your analysis to the wiki, under engines.