adapt carb from outboard? Puzzle.

[sjc204]

Hi,

Anyone following my recent posts will know I was planning to use a carb from a Honda outboard B100 (the 9.9HP version).

However now I have looked at it I have found an important difference. The outboard carb has a fitting (hose barb?) to take a rubber fuel pipe. This is fitted at 90deg on a tube that is tapered to make an interference fit (pressed in) in the hole in the carb body.

The MB2A carb has an extended shoulder on the hole, and the hole is threaded to take a bolt so that the banjo coupling can be screwed down (because the inboard uses a metal fuel pipe).

Has anyone successfully adapted an outboard carb to fit the metal pipe? I would like to know how.

I thought of tapping a thread into the hole. It is a blind hole so that could be tricky, but even if I can get the taps to do that, there would not be much thread and I would have to cut down the bolt, not leaving much to grip, and it has to take enough force to seal two copper washers. I doubt if a few threads in the alloy would be strong enough. I also thought about adapting the brass tube fitting to mate with the banjo fitting but I can't see a way to do that.

Any ideas anyone?

[Sarabande]

(20-04-2010 09:15 PM)sjc204 Wrote:  Hi,

Anyone following my recent posts will know I was planning to use a carb from a Honda outboard B100 (the 9.9HP version).

However now I have looked at it I have found an important difference. The outboard carb has a fitting (hose barb?) to take a rubber fuel pipe. This is fitted at 90deg on a tube that is tapered to make an interference fit (pressed in) in the hole in the carb body.

The MB2A carb has an extended shoulder on the hole, and the hole is threaded to take a bolt so that the banjo coupling can be screwed down (because the inboard uses a metal fuel pipe).

Has anyone successfully adapted an outboard carb to fit the metal pipe? I would like to know how.


Photo possible?
How about tapping then threading a thin walled tube as a connector?

Keep us posted as a doable replacement would help a lot. of people who suffer from carb problems on this forum.
I thought of tapping a thread into the hole. It is a blind hole so that could be tricky, but even if I can get the taps to do that, there would not be much thread and I would have to cut down the bolt, not leaving much to grip, and it has to take enough force to seal two copper washers. I doubt if a few threads in the alloy would be strong enough. I also thought about adapting the brass tube fitting to mate with the banjo fitting but I can't see a way to do that.

Any ideas anyone?

[John Smith]

(21-04-2010 06:24 AM)Sarabande Wrote:  

(20-04-2010 09:15 PM)sjc204 Wrote:  Hi,

Anyone following my recent posts will know I was planning to use a carb from a Honda outboard B100 (the 9.9HP version).

However now I have looked at it I have found an important difference. The outboard carb has a fitting (hose barb?) to take a rubber fuel pipe. This is fitted at 90deg on a tube that is tapered to make an interference fit (pressed in) in the hole in the carb body.

The MB2A carb has an extended shoulder on the hole, and the hole is threaded to take a bolt so that the banjo coupling can be screwed down (because the inboard uses a metal fuel pipe).

Has anyone successfully adapted an outboard carb to fit the metal pipe? I would like to know how.


Photo possible?


Keep us posted as a doable replacement would help a lot. of people who suffer from carb problems on this forum.
I thought of tapping a thread into the hole. It is a blind hole so that could be tricky, but even if I can get the taps to do that, there would not be much thread and I would have to cut down the bolt, not leaving much to grip, and it has to take enough force to seal two copper washers. I doubt if a few threads in the alloy would be strong enough. I also thought about adapting the brass tube fitting to mate with the banjo fitting but I can't see a way to do that.

Any ideas anyone?

---

Hi all.
I had a similar problem when I changed my original VP carb' for a new carb'. The new carb' is intended for a Honda outboard. The new carb' had a barbed spiggot to accept the fuel inlet pipe, whereas the old VP carb' had a tapped hole for accepting a banjo, this banjo joint coupled the VP carb' to the fuel pump via a steel pipe. Obviously, I couldn't couple the steel pipe to the new carb's spiggot.
I also needed a new fuel pump, which I bought, and found that it too was intended for a Honda outboard. Instead of a banjo joint it too had a spiggot, consequently, I was able to couple the new carb' to the new pump with a length of rubber(?) fuel tubing and discard the steel pipe.
On reflection, IF I didn't have to renew the fuel pump, THEN I would probably have cut the steel fuel pipe from the pump short at the carb' end, and extended it to the new carb's spiggot with a length of rubber fuel tubing. Had I done so, I would have had to bell-out the cut end of the steel pipe so that the fuel tubing could not easily slip off.

[sjc204]

(21-04-2010 10:21 PM)John Smith Wrote:  

(21-04-2010 06:24 AM)Sarabande Wrote:  

(20-04-2010 09:15 PM)sjc204 Wrote:  Hi,

Anyone following my recent posts will know I was planning to use a carb from a Honda outboard B100 (the 9.9HP version).

However now I have looked at it I have found an important difference. The outboard carb has a fitting (hose barb?) to take a rubber fuel pipe. This is fitted at 90deg on a tube that is tapered to make an interference fit (pressed in) in the hole in the carb body.

The MB2A carb has an extended shoulder on the hole, and the hole is threaded to take a bolt so that the banjo coupling can be screwed down (because the inboard uses a metal fuel pipe).

Has anyone successfully adapted an outboard carb to fit the metal pipe? I would like to know how.


Photo possible?


Keep us posted as a doable replacement would help a lot. of people who suffer from carb problems on this forum.
I thought of tapping a thread into the hole. It is a blind hole so that could be tricky, but even if I can get the taps to do that, there would not be much thread and I would have to cut down the bolt, not leaving much to grip, and it has to take enough force to seal two copper washers. I doubt if a few threads in the alloy would be strong enough. I also thought about adapting the brass tube fitting to mate with the banjo fitting but I can't see a way to do that.

Any ideas anyone?

---

Hi all.
I had a similar problem when I changed my original VP carb' for a new carb'. The new carb' is intended for a Honda outboard. The new carb' had a barbed spiggot to accept the fuel inlet pipe, whereas the old VP carb' had a tapped hole for accepting a banjo, this banjo joint coupled the VP carb' to the fuel pump via a steel pipe. Obviously, I couldn't couple the steel pipe to the new carb's spiggot.
I also needed a new fuel pump, which I bought, and found that it too was intended for a Honda outboard. Instead of a banjo joint it too had a spiggot, consequently, I was able to couple the new carb' to the new pump with a length of rubber(?) fuel tubing and discard the steel pipe.
On reflection, IF I didn't have to renew the fuel pump, THEN I would probably have cut the steel fuel pipe from the pump short at the carb' end, and extended it to the new carb's spiggot with a length of rubber fuel tubing. Had I done so, I would have had to bell-out the cut end of the steel pipe so that the fuel tubing could not easily slip off.

Hi, This makes sense and I could do exactly what you suggest. However, I can't help feeling the Volvo people used steel pipe for a reason. As the engine is inboard, it could be fairly serious if you have a leak of petrol (on the pressurised side of the pump) whereas with an outboard it is perhaps slightly less of an issue if it leaks/sprays petrol or even bursts into flames.

Would an inboard engine pass a survey if it had rubber fuel pipes?

[John Smith]

(22-04-2010 09:14 AM)sjc204 Wrote:  

(21-04-2010 10:21 PM)John Smith Wrote:  

(21-04-2010 06:24 AM)Sarabande Wrote:  

(20-04-2010 09:15 PM)sjc204 Wrote:  Hi,

Anyone following my recent posts will know I was planning to use a carb from a Honda outboard B100 (the 9.9HP version).

However now I have looked at it I have found an important difference. The outboard carb has a fitting (hose barb?) to take a rubber fuel pipe. This is fitted at 90deg on a tube that is tapered to make an interference fit (pressed in) in the hole in the carb body.

The MB2A carb has an extended shoulder on the hole, and the hole is threaded to take a bolt so that the banjo coupling can be screwed down (because the inboard uses a metal fuel pipe).

Has anyone successfully adapted an outboard carb to fit the metal pipe? I would like to know how.


Photo possible?


Keep us posted as a doable replacement would help a lot. of people who suffer from carb problems on this forum.
I thought of tapping a thread into the hole. It is a blind hole so that could be tricky, but even if I can get the taps to do that, there would not be much thread and I would have to cut down the bolt, not leaving much to grip, and it has to take enough force to seal two copper washers. I doubt if a few threads in the alloy would be strong enough. I also thought about adapting the brass tube fitting to mate with the banjo fitting but I can't see a way to do that.

Any ideas anyone?

---

Hi all.
I had a similar problem when I changed my original VP carb' for a new carb'. The new carb' is intended for a Honda outboard. The new carb' had a barbed spiggot to accept the fuel inlet pipe, whereas the old VP carb' had a tapped hole for accepting a banjo, this banjo joint coupled the VP carb' to the fuel pump via a steel pipe. Obviously, I couldn't couple the steel pipe to the new carb's spiggot.
I also needed a new fuel pump, which I bought, and found that it too was intended for a Honda outboard. Instead of a banjo joint it too had a spiggot, consequently, I was able to couple the new carb' to the new pump with a length of rubber(?) fuel tubing and discard the steel pipe.
On reflection, IF I didn't have to renew the fuel pump, THEN I would probably have cut the steel fuel pipe from the pump short at the carb' end, and extended it to the new carb's spiggot with a length of rubber fuel tubing. Had I done so, I would have had to bell-out the cut end of the steel pipe so that the fuel tubing could not easily slip off.

Hi, This makes sense and I could do exactly what you suggest. However, I can't help feeling the Volvo people used steel pipe for a reason. As the engine is inboard, it could be fairly serious if you have a leak of petrol (on the pressurised side of the pump) whereas with an outboard it is perhaps slightly less of an issue if it leaks/sprays petrol or even bursts into flames.

Would an inboard engine pass a survey if it had rubber fuel pipes?

Hi.
Well, I'm not a surveyor. Of course, petrol always poses a risk. The flexible tubing is clearly marked as for fuel, so we must assume that it is fire resistant up to a point. The tubing is available from most car spares shops and is intended for motor vehicles, which are also prone to catch fire.
There may be a marine grade of fuel tubing, possibly armoured, that I am not aware of.
I am told that a gas detector will also respond to petrol fumes, and I am sure that we all know that it only takes one drop of petrol to cause a stink.
Anyway, as my petrol tank is somewhat higher than the fuel pump, the fuel is more gravity fed than pumped.

[sjc204]

Hi.
Well, I'm not a surveyor. Of course, petrol always poses a risk. The flexible tubing is clearly marked as for fuel, so we must assume that it is fire resistant up to a point. The tubing is available from most car spares shops and is intended for motor vehicles, which are also prone to catch fire.
There may be a marine grade of fuel tubing, possibly armoured, that I am not aware of.
I am told that a gas detector will also respond to petrol fumes, and I am sure that we all know that it only takes one drop of petrol to cause a stink.
Anyway, as my petrol tank is somewhat higher than the fuel pump, the fuel is more gravity fed than pumped.
[/quote]

Hi,

One of you asked for a photo. Hopefully you will be able to see my photo of the outboard version carb. I can't get a pic of my boat carb just now, but for the MB2A version you can look at your own or the drawing on p8 of the manual. You can just see that the hole extends outwards. What I want to do is to find a way to connect the existing banjo connector to the carb if possible. (Ignore the picture on p9 which is on an outboard)

I don't really want to get into a discussion about fire safety but I'm pretty sure fuel grade tube is just made of a sort of material that doesn't dissolve with petrol. I don't think it is in any way fireproof (but I might try burning some later). Whether the fuel supply is pumped, or pumped with gravity assist, it will surely have enough pressure to get out of a crack / cut. (The gravity assist only means it will still come out when the engine stops.) So my first preference is to stick with the steel if poss.

Thanks for the thoughts so far, any more ideas about connecting the pipe would be welcome. And if I find a good method I'll post it for everyone.

[Amazon]

Hi

The original pipe was metal as previously stated to reduce the risk of fire with an inboard engine installation. One way to go with this if the carb and or pump has been changed for the outboard type is to have a braided stainless fuel pipe made up with the exact end fittings desired by a specialist company who operate in the motorsport industry. Current regulations do not allow simple fuel hose, I feel sure these fuel lines are more than adequate and are not expensive.

regards Ron

[Ciao Bye]

Don't forget a fuel valve, that's what the surveyor told me to install on my fuel line as to cut the suplly of fuel to the engine in case of....


John
Quebec
Canada

[billyjmcd]

We have a surveyor on our marina and i asked him yesterday about the fuel line and he said it was o.k. to use PROPER fuel line [it is marked on the line] but it must not lie against anything hot.
I already have done this, i cut the pipe from the pump after the bend and 40mm from the carb. so that the hose is in a straight line then jubilee clipped it.

[sjc204]

Hi,

I have now done the job by cutting the steel pipe and connecting a length of rubber fuel hose. Just like Sarabande suggested (or was it John Smith? sorry). I've used jubilee clips to make sure the rubber cannot slip off the end of the metal pipe, and I crushed the end slightly to make it wider to present a barrier to the rubber sliding off.

Anybody needing to do this might like to know that the spigot is so close to the body of the carb that only a thin pipe can be used. There is some heavy duty fuel hose on sale which I really liked, but it would not fit on.

Another apology, now I have fully compared the VP carb from the MB2A and the Honda carb off a BF100 outboard. Sorry, the casting is the same, the body does not extend further on the threaded one. So, if you can cut a thread in an outboard carb you will be able to connect the banjo connector with a fuel line (hollow) bolt. The thread appears to be M10x1 (the fine thread version of M10). I decided not to do this in case I ended up with machining waste inside the fine drillings of the carb, and I already have enough trouble, I wanted to make sure I knew the carb was in working order. But this does seem to be a practical solution, if you have access to the equipment.

One other note on this, I do have the fuel tank higher then the engine. I have never liked that aspect, and I do have a stop valve accessible fromthe cockpit that can stop the flow of fuel.

The engine has run since, but I still have other problems!