Kubota EB300 questions - marinization for boat genset/watermaker

[rymann]

I'm building a genset/watermaker for my boat based on an ebay EB300 and I've got plenty of questions that I'd like to put to the collective wisdom of the group.  I've been working on petrol engines for years but don't have much experience with small diesel engines.  I've taken a look at MV Viking Star's blog site - I think the owner is on this board as well.

The unit will be used in temperate to hot weather in a saltwater environment.  It will be installed in a small space so I will use a heat exchanger and probably an exhaust blower for ambient heat.  The fuel tank will probably be mounted below the engine so I will use an external fuel pump.

I've only seen a few heat exchangers for these engines and have seen various complaints about build quality.  The nextgen unit is available for about $400 and seems to be the best bet - any experience or better yet does anyone have a secondhand one they'd like to unload?

Are most accessories interchangeable between the EA300 and EB300 (I'm thinking mainly of radiator/heat exchanger)?  While I'm at it, I have the manual for the EA300, what are the main differences between the two?

Fuel:

I'd like to simplify the fuel system - there are 5 lines to and from the tank.  Can I removed the jet-start system and reduce to a single feed (inline pump and filter) to the injection pump and single return from the injector?

For the fuel pump - what's the acceptable range of supplied fuel pressure/flow rate since I won't be using gravity feed?

Exhaust:

The exhaust port on the Kubota is about 30mm ID.  Can I use 30mm ID exhaust pipe and tubing throughout (and for the waterlock), or should I upsize after the mixer since my raw water pump will be putting through 4-6 GPM of cooling water?

Vetus has waterlocks, mufflers, goosenecks, and anti-siphon devices which together seem like overkill for a small system (at a high cost).  Can I get away with just a waterlock if 1) the heat exchanger is a foot or so above water level, and 2) I put a high loop in the exhaust hose between the waterlock and the overboard outlet?

Thanks in advance for any insight.

[thomasonw]

Rymann,

Hello - and good luck with your project!   Will answer below some thoughts I have from doing our project on Viking Star.

-al-


;I've only seen a few heat exchangers for these engines and have seen various complaints about build quality.  The nextgen unit is available for ;about $400 and seems to be the best bet - any experience or better yet does anyone have a secondhand one they'd like to unload?

I looked for a LONG time for a 2nd hand heat exchanger, and even looked into trying to build one - or use say an external exchanger, ala one that is designed for transmission coolers.  IN the end I just ended up purchasing one from an integrator as the complexity (extra pumps, hoses, etc) seemed a bit over the top.  I used the one from Next Gen as I found it to be much lower in cost then other integrator, but I have had issues with it leaking coolant - the flanges a too thin and warp when tightening things down. other then that it seems like a good unit.   I have soldered on stiffing brass and think that will help.  (Will post again in mvVikingStar.blogspot.com the results)


;Are most accessories interchangeable between the EA300 and EB300 (I'm thinking mainly of radiator/heat exchanger)?  While I'm at it, I have the ;manual for the EA300, what are the main differences between the two?
I too have wondered the difference


Fuel:

;I'd like to simplify the fuel system - there are 5 lines to and from the tank.  Can I removed the jet-start system and reduce to a single feed (inline ;pump and filter) to the injection pump and single return from the injector?
I removed the jet-start as well as all the filter / valving and ran fuel lines directly to the pump and from the injector.  Lookling back I think I would have kept the filter and the lines to/from the pump/injector for two reasons: 
1) Can never really have too much filtering!
2) The return line off the injector is very very small, and I have not found marine rated hose that matches it.  Close, but not 100%  As a result I have had some issues with leakage.

Doing it again, I would have left the original filter and hosing and then ran my boats fuel feed and return lines to the filter.


;For the fuel pump - what's the acceptable range of supplied fuel pressure/flow rate since I won't be using gravity feed?
I just used a standard (from Napa) fuel pump.  I think  it is in the 3-5lbs range, do not see any issues.



;Exhaust:
; Several questions

For the exhaust I used 3/4" pipe for the hot side and 1.5" after mixing in the cooling water.  This was selected, to be honest, to match up with the existing transom exhaust port from a prior generator.  Have seen no issues or indication of struggles with the motor.  We have only a water lift muffler combined with very generous and high looks.  I do no like adding too much into the exhaust system which will increase back pressure (like check valves, etc), but one does want to make sure there is little change of water being pushed back up from say following seas.

Our motor is mounted well above the water line, so no need to worry about the inlet side, but being 1' above it might be a good idea to add a vacuum brake after your raw water pump and before anything else.


-al-

[rymann]

Hi Al, just saw your response, thanks.  I got some good info a while back from our blog - I am almost exactly in the stage of your #1 of 20 pictures.  Bending my brain on the best platform/mounting  for the space I have right now.

I am installing this in a medium sized lazarette (I may box it in with some insulation and a blower depending how loud it is) - I did get the nextgen exchanger.  Do you find it does the job?  There are also two nuts on the side in the freshwater part which I guess could be used for external circulation.  Your set up and some of the commercial versions out there seem to run the raw water pumps at 1:1 or so with the crankshaft... at 2800 rpm (although I think you run at 1800) that could be 30+ lpm which seems like a lot for a 6hp engine and I would guess not great for the impeller.  I think I have the same waterlift you have, a 1.5" Vernalift - no problem with that amount of water for yours?

I also ordered a return fitting from Nextgen thinking it would have a larger nipple (it may) - but it has two fittings, one of which the rep said goes to the air bypass line on the injector pump.  Not sure this is necessary except maybe to bleed the system?  Stock set up has only the one return.

I'm using a Facet fuel pump and got a second one to use as a transfer pump from my main diesel tank.  We'll see if it's strong enough to push 15 feet or so after a filter.

Ryan

[thomasonw]

Hello.

I found the Nextgen exchanger works well, but hard a hard time keeping the mounting flange from warping and leaking.  I have just finished soldered on some brass stiffeners to it and bolting things back up.  Will see if this helps.   You might consider adding stiffeners as well.  (Will post an update to blog in a day or so showing photos).  On the side nuts, yes I think they could be used for circulating and/or temp gauge.   I found out (by actually removing it) that the drain valve in the bottom of the Kubota is actually standard USA NPT thread!  (1/2" IIRC), so hooking up a heat take-out would not be that tuff.

On raw-water pump, I am pumping a LOT more water then needed to just cool the motor as I also use that same pump as the pre-filter boost pump for the RO water maker.  Per the Jabsco spec, I should be pumping around 6-7GPM.  If you are going to use a separate pump for the pre-filter boost pump, likely you can use a smaller raw-water pump to cool only the motor.  I have also seen where someone cut the housing around the hand-crank shaft to expose it, and then mounted the raw-water pump to it using a hard coupler.  This hand-crank shaft runs at 1/2  the motor RPMs.

I have had no issues with the current amount of cooling water and the lift muffler.  Overall it lifts about 3.5' before dropping back down and exiting the transom.

Do not know anything about the Nextgen return fitting, perhaps you can post a photo when you get it?  By Air by-pass, are you talking about the fuel line that goes to a small wheel valve in the air intake?  According to the service manual, this is called the Jet-Start and is used to assist with really cold (-20c) starts - I just blocked it off and use only the glow-plug.  When bleeding I only cracked the fuel feed line at the injector pump, the Kubota seemed do the rest by its self.

-al-

[rymann]

I'll let you know how it goes.  As for the hand crank, I didn't know it was half speed, that would help a lot.  I would rather have all belts on the other side of the engine but it may not be possible - I am thinking about putting a pulley on that shaft, removable with one bolt to use for hand cranking if the starter fails in an emergency (could rig up an electric pump for raw water circulation temporarily).  I would have a pulley welded to a tube about the same ID as the OD of the shaft, with slots for the hand crank pins, then drill and tap a hole in the end of the shaft for a retaining bolt.  Still not sure that's a great idea.  Cutting the housing is an option, too.  The pump

About the air return, I obviously don't know anything about it either... I've taken off off the jetstart so it may not be necessary.

[rymann]

I took a closer look at the layshaft yesterday - it's actually even more than 2:1, maybe 2.5:1.  I will mark it and measure better, I didn't see a reference in the manual.

I started to say in my last post that the pump is rated for about 10-20 lpm at 1150rpm which seems reasonable for this engine.

[thomasonw]

2.5:1!   Oh, that would be great to know the exact RPM as it is the most convenient shaft available to me for touching my tach to!  Will be interested in what you find out.

IMHO, I would think 10-20 lpm would be just about right for cooling purposes.  Will watch to see if you get a more accurate ratio number for the lay shaft.

-al-

[thomasonw]

BTW:  I just went out and marked my Kubota.  The main spun 5 times for two complete turns of the lay-shaft.  So, I get 2.5:1 exactly!

-al-

[rymann]

Thanks for checking - 2.5:1 will make a good 1120 rpm for my impeller pump.

I was going to modify the flywheel takeoff I have by adding a splined shaft and have k6 and 1/2" pulleys made up but the first machinist's quote was outrageous (I am in Hong Kong so I'm limited by language where I can go) - $550 for the shaft/pulley assembly and $55 for a simple mild steel bracket, so I think I will try to find the Kubota takeoff that you used and find standard pulleys.  Did you order direct from Kubota in Japan?

There's a pic below of the new fuel return fitting - the nipple is bigger than standard so hopefully that will make hose sizing easier.  Not sure what I will do with the other nipple since I am using an external tank/filter  but maybe it can be a bleed valve.

I think this guy (pic attached) has the right idea for the alternator bracket.  I will make a template unless someone knows if it is commercially available.

Ryan

[rymann]

The alternator bracket:

[thomasonw]

Oh, that fuel return is so nice!  I assume the part number is 15841-94040   Do wonder if there is a single port version.  (Could one of the ports be brazed closed??)

For the Spindles, here are the Kubota part numbers I know of:
19501-8451-2   1-1/2" x 3.5" PTO shaft
19501-8451-0   1-7/16" x 3.5" PTO shaft
14972-8451-2   1-3/16" x 2.17" PTO shaft
14943-8441-3   46mm x 90mm PTO shaft

There are other options, but by using one of these spindles one can select the pulley the want.

I purchased these from EC Power in Portland Oregon  (www.ecpower.com), but I suspect any Kubota small engine dealer can get them.  On that, it does seem there is a difference between Kubota small engine dealers and say Kubota tractor dealers.  I get the impression they might be different divisions...  I would think the Kubota website would be able to point to a dealer in the HK area.

And that Alternator bracket looks real clean.  Does it allow for the belt tension to be adjusted?  Or perhaps a separate belt tensioner is used on a flat belt?


-al-

[thomasonw]

OK, so it looks like Kubota 15841-94040 is just the sealing washer.  What is the part number for the injector return assembly with the larger ports?

[rymann]

Thanks, I'll try E C Power.  Since I'm buying some parts in the US (like a lot of brass fittings I got while home at Christmas) and some here, I will have mismatched metric/english sizes - will surely confuse anyone who tries to work on it in the future.  I'm trying to keep the alternator for the genset and for my main engine similar so that they can be exchanged as spares - both alternators (a Balmar 110A and an Electromaax 160A) have K6 serpentine belts so I will have to try to find a big (7") serpentine belt pulley that will fit on the Kubota shaft.

I hadn't seen the surpluscenter.com catalog before, impressive.

Yes, the label on the small plastic bag is just for the washer... I don't have the part number for the return assembly, but I ordered it from NextGen.  They use it on their gensets so I'm sure they could tell you.  (I just pulled out my NextGen receipt - the other Kubota parts have Kubota parts numbers but the return fitting part number is SCSRETURN-FIT so it may be their own part.)

As for the alternator bracket, I would have the top bolt hold a flat adjusting bracket and have the alternator pivot on the lower mount.  The photos I included are from a classified ad I came across.

Ryan

[rymann]

Al, one more question - does the Kubota shaft have a key?

[thomasonw]

The parts manual I have shows a keyway for the 1-1/2" and 1-3/16" shafts.  I ended up using the 1-7/16" shaft (EVERY digit is important in these part numbers it seems  ) and it too has a keyway.   

I would ASSUME the metric shaft does as well, but the parts book I have on hand does not show that part.  (I had copied the part number down while visiting EC power one day..)

Thanks for the heads up on on the injector return via NextGen power.  Perhaps that is one thing these ran across as a problem as well!

-al-

Al, one more question - does the Kubota shaft have a key?