Yamaha Carburetor Swap

[ChuckB1954]

The bottom #4 carb on my '99 F50 is gummed up and need cleaning. Engine only running on upper three cylinders. Evidence of wrenching on all of them. I have another set of carbs from a F40 in new condition. The jet sizes are the same in both carbs according to my manual. What can I expect if I do the swap? Should I forget about it and just disassemble and soak the original carbs?

EDIT--------------------------------------------------------

Looking at the Boats.net parts diagram, I found they are identical! Same part number.

[boscoe99]

------------------

[boscoe99]

You might want to take a look at the Yamaha USA parts catalogs for an F50TLRX and an F40TLRX.

[ChuckB1954]

I called boats.net and they assured me that it has the same part number and therefore they are interchangeable. I will do some more research though.

[boscoe99]

You could have already done your research by simply looking at the Yamaha USA parts catalog at their website.
f50.jpg

[99yam40]

The bottom #4 carb on my '99 F50 is gummed up and need cleaning. Engine only running on upper three cylinders. Evidence of wrenching on all of them. I have another set of carbs from a F40 in new condition. The jet sizes are the same in both carbs according to my manual. What can I expect if I do the swap? Should I forget about it and just disassemble and soak the original carbs?

what makes you think they are in better shape than the ones on your motor now?

where did they come from?

I would be cleaning the ones you already have at least you know they have run well in the past when clean, the others, you have no idea what could be wrong with them

You do know that you will need a vacuum mate tool to set them after cleaning

[ChuckB1954]

You could have already done your research by simply looking at the Yamaha USA parts catalog at their website.

Thank You !

[ChuckB1954]

what makes you think they are in better shape than the ones on your motor now?

where did they come from?

I would be cleaning the ones you already have at least you know they have run well in the past when clean, the others, you have no idea what could be wrong with them

You do know that you will need a vacuum mate tool to set them after cleaning

It's very obvious they are in much better shape than my old carbs! Clean inside and out. The bowls look new inside. My old carbs have corrosion inside the bowls.

I bought them on ebay just to get the prime starter, solenoid and other obsolete parts that were missing from my engine when I got it. Here's what they look like after I assembled them with new o-rings, ready to bolt on. I was going to install them tomorrow, but looks like I will be taking them apart again. Don't want to damage my engine by installing them and seeing "what happens". All the pieces other than the carb bodies are identical , so I will use everything, including the bowls to make a compatible set.







This is what led me to believe that they were interchangeable. Maybe I misinterpreted it, but it seems kind of misleading.

[ChuckB1954]

It's very obvious they are in much better shape than my old carbs! Clean inside and out. The bowls look new inside. My old carbs have corrosion inside the bowls.

I bought them on ebay just to get the prime starter, solenoid and other obsolete parts that were missing from my engine when I got it. Here's what they look like after I assembled them with new o-rings, ready to bolt on. So from boscoe99's post, the only carb that is different is # 4?? I did notice the linkage is different. It only allowed the carbs to open 3/4, unless you bent the tab.

image_4937.jpg

[ChuckB1954]

The only differences that I can tell between the 50HP and the 40HP #4 carb is the throttle linkage. The disassembled carb on the left is the 50HP.

CaptureLinkage.JPG

Until I bent the tab on the 40HP carb, this is as far as it opened:

Capture34.JPG

The tab I bent can be seen in the center. As with the 50HP carb, the inlet flange casting is used as a stop.
Capturetab.JPG

[zenoahphobic]

This is probably an example where the engine is capable of 50 horses and they also made a 40 by restricting the full opening of the throttle butterfly (ie limited to approximately 80%)

[99yam40]

very interesting,
well let us know how it works out

get your hands on a carb tune vacuum tool

I just went back a reread your other posts on this motor and you never did update them on how the motor ran and props worked out.

and I never did see where you used the proper tool to set carbs either

[ChuckB1954]

This is probably an example where the engine is capable of 50 horses and they also made a 40 by restricting the full opening of the throttle butterfly (ie limited to approximately 80%)

It appears that way. The major engine components are the same on both engines. (Block, pistons, heads, crankshaft, etc). But why would they do this?

[boscoe99]

It appears that way. The major engine components are the same on both engines. (Block, pistons, heads, crankshaft, etc). But why would they do this?

If a boat is rated for 40 HP and the owner wants max power he gets the F40. If a boat is rated for 50 HP and the owner wants max power he gets the F50. It makes it easier for Yamaha to give the customer what the customer wants at the cheapest cost to Yamaha.

The Offshore F225/F250/F300 are identical except for the engine control unit. Same thought process.

[ChuckB1954]

If a boat is rated for 40 HP and the owner wants max power he gets the F40. If a boat is rated for 50 HP and the owner wants max power he gets the F50. It makes it easier for Yamaha to give the customer what the customer wants at the cheapest cost to Yamaha.

The Offshore F225/F250/F300 are identical except for the engine control unit. Same thought process.

Someone probably paid 100's more for the F50 not knowing this. If it ever quits raining I am going to bolt these on and try it.