Convert 1993 4 HP to remote tank

[Aussieken]

I wish to convert my 1993 Evinrude 4hp 2 stroke to run on a remote tank instead of the internal tank it now has.
I found this thread here which is helpful in identifying parts and explaining some things.
https://forums.iboats.com/threads/1999-johnson-4-hp-how-is-this-supposed-to-work.612401/
From the drawings on this thread:
Some of these motors have both internal and external fuel tanks and the petrol enters the carby at different points. The internal tank will supply fuel to the bottom of the carby , whereas the fuel from the remote tank goes through a pump then to another point on the carby that is above the inlet from the internal tank.

My carby does not have the extra nipple for the fuel hose from the pump, it is blocked off with a brass plug.

Is it possible to fit a pump, run fuel from the external tank to the pump and then run the fuel from the pump to the existing nipple currently used by the internal tank?
Also, my motor does not have a fuel pump but it does have a pulse tube running from the crankcase to the carby, next to the fuel inlet. Does this act like a pump ?

If I were to fit a fuel pump I would have to disconnect the existing pulse tube at the crankcase as this is where the pump gets it pulse from. So I am guessing that I would have to block off the point that the pulse tube is currently connected to the carby?

I would appreciate any advise regarding this conversion.

Thanks.

 

[Vic.S]

reply deleted

 

[racerone]

There is a " pumping bladder " in your carburetor now I believe !

 

[Crosbyman]

Hong Kong made 3.3hp with tank or 4hp ??? what is your model # most 4hp seems to have a pump / ext. tank already

whereas the 3.3hp is e/w an integral tank

 

[racerone]

I say this engine is the latest version of the 2 cylinder 3 / 4 HP block.----First marketed in about 1953 or so.

 

[Crosbyman]

agree for the 4hp yet the parts place.... shows most 4hp come with the usual square pumps the little 3.3 H models from Hong Kong have top tanks .
I recently worked on a HK version (broken side panel NLA)

waiting for Aussieken reply on mdl #

 

[racerone]

These come with a little bladder ( fuel pump element ) in the carburetor.-----Assist the gravity fed carburetor to maintain correct fuel level.

 

[Aussieken]

Thanks for the replies. It is a 4 HP ( Belgium manufactured) with only an internal tank, so it does not have a pulse pump fitted ,that is why i want to convert it to use a remote tank.
The internal tank does get assistance from the crankcase, which is a rubber hose from the crankcase to the carby, but there is no separate fuel pump.
I Have decided to buy a small pulse pump, attach the hose from the current connection to the crankcase, run a fuel line from an external tank to the inlet of the pump and a fuel line from the outlet of the pump to the carby.
Now it's just deciding on which pump to get as the original Evinrude /Johnson pumps are no longer available.

 

[racerone]

The little square fuel pump was first used on 1968 model 3 HP.------Used on many motors up to 25 HP.----Used for many years.-----Should be available all day long.---See your local boat shop they will likely have some on hand.----Used ones are everywhere.-----Simple to install a new diaphragm at about $6 US , as that is about the only thing that can fail on them !

 

[Scott Danforth]

same small little pumps also on various outdoor power equipment

 

[Aussieken]

Thanks racerone, unfortunately they don't seem to be available here in Australia. I have looked at a few US parts suppliers and their sites say that the part is unavailable as well.
I have contacted outboard wreckers here and no secondhand ones available.
One wrecker can sell me a new pump ( generic) which he says will do the job, so will try it. Could be a couple of weeks before I can get it though.
So I think this is what has to be done.
When fitted I will no longer require the internal tank so I will disconnect the fuel line at the carby and replace with line from the pump, and as the pulse will be operating the pump I will block off the line to the bladder port.
And of course fit a fuel fitting to front of engine and run fuel line to fuel in port of the pump.

 

[racerone]

The little square pump is available all day long !!----Do not limit your search to a 1993 model.-----Used from 1968 to 2005,------3 HP to 25 HP.------Now it may have something to do with mounting hole screw being oriented a different way.----eg--The 1992 model 9.9 uses it.---And the 1973 model 25 HP uses it.

 

[Scott Danforth]

@Aussieken they are available nearly everywhere. just do a generic search for outboard engine fuel pump. https://www.amazon.com/s?k=outboard+motor+fuel+pump&ref=nb_sb_noss_1

here is an aussie site https://boatbits.com.au/marine-parts/fuel-pumps/omc-fuel-pump-18-7350.html

I converted an old 12hp gale for dad about 30 years ago to a remote tank with one from a 15hp johnson that I picked up at a local dealer. I believe it was a 1950's model so the pump was used prior to 1968

as @racerone said, they are everywhere.

 

[racerone]

These pumps operate with a PRESSURE pulse.-----Likely can be fitted on a 1920 model Evinrude.----I just installed a needle bearing crankshaft in a 1959 .Evinrude 5.5 HP fitting one of those square pumps is next !----Have a bunch of them and all they can need is a new diaphragm.

 

[Aussieken]

Thanks again racerone and Scott. I looked at the links and whilst the new pumps look the same they do say that they are for "pre" 1993 motors and they show the part numbers that they cover, however not the part number for mine which is 0434521. Also the inlet and outlet spigots are a different size whereas I am sure that mine should be the same size. There is a second hand one on ebay that the seller is part number 0434521 and both spigots are the same size.
The dealer I spoke to here says that his new pumps are a direct copy of the originals. I will see if is are ok in a couple of weeks.

 

[racerone]

This should be simple to resolve.

 

[Aussieken]

OK. it has been a while. Got the pump and installed it. Fired up and ran for a while then died. Every time I wanted to start it I would have to prime the bulb. It seemed like it was only running on the fuel that was primed into the carby. Needed to check if it was pumping fuel. Thought about it over a week and then decided that the way to check would be to use clear plastic line for the fuel lines. Ran plastic lines from the fuel tank connection to pump and from pump to carby.
Primed and I could now see fuel going to the pump and then through the pump to the carby. Great. Started the motor and could see that air bubbles where coming into the fuel line at the pump outlet. Didn't seem to be a lot of fuel going into the tube. I suppose that it would not be pumping a lot anyway as it's only a small motor. After a while it cuts out again.
I thought about it for a few more weeks and decided that there must be a leak in the pump and it must be sucking in air. So decided that I may have to pull the pump apart and see that all was in order. Looked on the net and found some tutorials which gave me confidence to do it.
One thing that they said was that the 2 "drain" holes MUST be pointing down. I had not noticed any drain holes but on closer inspection seen them.
The way this pump was configured with the inlet/outlet , one of the holes was pointing up. This could be because on my motor the two bolt holes that attach the pump to the motor are vertical ( one above the other) whereas on the older models they were horizontal.
Also, the tutorials advised that to check the pump, you should be able to blow through the inlet and have air come out of the outlet, but you should be unable to blow any air through the outlet. I could blow air through both. Not Good.
I stripped the pump down and configured it so that the drain holes were both pointing down, all gaskets, springs etc. all in correct place. However I could still blow air through both inlet and outlet. Why???
There was nothing more I could do with it so put it on the motor and tried it out. I primed it up, no leaks from the pump, started the motor and pretty much straight away I could see some bubbles forming in the tube at the outlet. Not as much as before and as the bubbles formed a bit more space I could see a trickle of fuel. Revving it produced more bubbles and probably a bit more fuel. In the end it died even though there was still some fuel in the line at the carby.
Does anyone have any thoughts. Why can I blow through both inlet and outlet???
Any advise would be appreciated.
Cheers.

 

[Crosbyman]

chinese pumps??? .....I had issues with some rebuiling is tricky to say the least


how did you mount the pump ??? the square pumps are pulsed from the rear with a gasket

pictures ???

if you have a pulse line you can try a sqware mikuni pump also

 

[Aussieken]

Thanks Crosbyman. Yes it is a Chinese pump. It is mounted directly on to the motor so the pulse is direct to the pump with the mounting screws above and below the pulse hole with quite a thick gasket that was supplied.

I have attached photo ( I Think)
The original set up had a nipple screwed into the pulse hole with a tube to the carby that operated some sort of bladder? That line is to the left of the fuel inlet at the carby and is now blocked off. See photo.
I have been thinking of trying a Mikuni, they seem a lot more simple design and would have to be a better quality. It seems that the smallest model they do pumps at 14 liter / hour. I am concerned that that would be too much but maybe that is the maximum that it can do and that the 4 HP Evinrude would only pump what it requires.
Have you had any experience with them? To use it I would reinstate the pulse nipple and run a hose to the pulse port on the Mikuni.
Any suggestions would be welcome.

 

[racerone]

They made / installed those pumps from 1968 ( 3 / 6 / 9.5 / 18 HP ) to 2005 on many models.-----I can't believe that some folks consider them to be no good.-----The only thing that can go wrong with the pump is the diaphragm !----Easy to find and replace at $5.06 each.------I can't believe that they sell thousands of these pumps on E-bay / Amazon .-----These pumps only pump what the float valve lets in !!