!972 Mercury 650 65 hp 4cyl I am guessing carb trouble? Please help

[kevinelt]

This motor starts fine then comes up to speed normal ... and reaches plane. I can hold it open as long as I want but then after slowing back down to a stop, it wont come back up to speed it acts like some cylinders are not firing. And runs badly sputtering. I notice excessive fuel coming out bottom carb like fuel is being pushed back through the carb. I thought the float might be stuck but I put pressure on the ball and it gets hard with no leaking from carb. Does anyone have an idea of what is wrong? Please help. any suggestions would help.

 

[MacDaddy21]

Re: !972 Mercury 650 65 hp 4cyl I am guessing carb trouble? Please help

Sounds like you need to rebuild your carbs, then do a link and sync. Might want to get a manual if you don't have one.

 

[hotrod53]

Re: !972 Mercury 650 65 hp 4cyl I am guessing carb trouble? Please help

^ Agreed, rebuild parts aren't expensive and it would be good reassurance. Sierra sells carb kits, you need a seperate fuel pump kit, and if you have Tillotson carbs with the blue inlet piece, replace that too. I paid < $7 for each of the 4 kits required and $5 each for the blue inlets.

Be careful with the carb link, it is fairly fragile yet still available for $16.

 

[MercMan82]

Re: !972 Mercury 650 65 hp 4cyl I am guessing carb trouble? Please help

Can I ask where that link can be found?

 

[kevinelt]

Re: !972 Mercury 650 65 hp 4cyl I am guessing carb trouble? Please help

I removed the bottom carb its stamped kc15 t the top is stamped kc15. I removed the top of the float bowl and noticed a small spring on the top of the float it was bent in half like an elbow. Looks like it is supposed to engage the needle valve I can see the wear marks in the needle lever (circular). Could this be the problem with too much fuel? If you have worked on this carb before please tell me? Is the fuel level inside the float bowl Really that sensitive? I was able to straighten that spring. My thoughts are the float was being jambed up into the lever when I pump up pressure by the ball, causing normal shut off. But when running maybe that bent spring was causing an abnormal fuel level or maybe an unbalanced supply. Any thoughts?

 

[ThumbPkr]

Re: !972 Mercury 650 65 hp 4cyl I am guessing carb trouble? Please help

For what it is worth I think the 1972 650 was a three cylinder,first year for them.Ron G

 

[kevinelt]

Re: !972 Mercury 650 65 hp 4cyl I am guessing carb trouble? Please help

For what it is worth I think the 1972 650 was a three cylinder,first year for them.Ron G

maybe its a 71 but its 4cyl

 

[merc850]

Re: !972 Mercury 650 65 hp 4cyl I am guessing carb trouble? Please help

Here's how to set the float height and the only spring in those carbs is inside the float. It's possible someone pulled it out by accident when checking the carb.