2006 johnson 90 carb bowls?

[gahunter706]

I have a 2006 Johnson 90hp that I keep having an issue with the carb bowls warping and leaking. All 4 bowls were slightly warped and leaking when I purchased the motor, so I rebuilt the carbs and put new bowls on them. That lasted for a couple months, then they slowly started warping again and leaking. I ended up taking it to a dealership to fix it because I just didn't have the time to mess with it, as well as the motor having an ignition problem I couldn't figure out. They rebuilt all 4 carbs, put new bowls on them, and replaced the power pack and the key switch. Motor ran great for little over 3 months, then the carbs yet again started warping and leaking. Is there a way to keep these carb bowls from warping, or maybe a metal replacement for them? I had read that over tightening the screws on the bowl could cause it to warp, but I made sure to torque them down to spec, which I believe was in the 20 in-lb range, when I rebuilt the carbs the first time. Any help would be greatly appreciated.

 

[Chris1956]

Gee, I am in the process of replacing the carb bowls on m'98 Johnny 150. They lasted since the motor was new, so I am hoping the new ones last as long.

​Is it possible your motor is running hot, causing the bowls to warp?

 

[gahunter706]

Gee, I am in the process of replacing the carb bowls on m'98 Johnny 150. They lasted since the motor was new, so I am hoping the new ones last as long.

​Is it possible your motor is running hot, causing the bowls to warp?

I don't think it is running hot, it pees a good stream of water and I haven't got any alarms from it.

 

[oldboat1]

Pure guess, but maybe the carb tops are warped. You could remove the carbs and split tops and bottoms, possibly checking each on a perfectly flat surface (piece of glass or mirror). I'm pretty sure the bowl has a ridged mating surface -- not sure about the carb top. If the top is smooth, you could probably resurface it like you would a head cover (fine grit sandpaper on a sheet of glass).

 

[Chris1956]

Oldboat, That is a good suggestion. The carb bowls do have a raised ridge to seal against the gasket. On my warped bowls, the bowls were only warped on the sides, but were warped enough to allow fuel to leak, despite a pretty thick (1/8"?) gasket. The front and rear sides of the bowls did not seem to be warped or at least not as much.

​Could you describe why a warped carb would warp the bowls to cause them to leak?

 

[gahunter706]

I will definitely check to top mating surface on the carbs to see if they are straight when I take them apart. Mine, like yours Chris, are only warped on the sides. Mine aren't too bad right now, warped just enough to let some gas seep out, and the motor still runs decent. But as I figured out last time, they will continue to warp and leak more and more, leading to a motor that hardly runs.

 

[racerone]

Dealer mentioned that he has instructed his guys that tork on the screws is 10 inch lbs.

 

[gahunter706]

Dealer mentioned that he has instructed his guys that tork on the screws is 10 inch lbs.

Thanks, I will make sure to torque the new bowls to 10 inch lbs. I can't remember what I torqued them to the first time, but I know it wasn't over 20 in-lbs. No telling what the dealership torqued them to when they put the second set of bowls on it, but they have always done good work for me so I don't think they would have over tightened them too bad.

 

[oldboat1]

Oldboat, That is a good suggestion. The carb bowls do have a raised ridge to seal against the gasket. On my warped bowls, the bowls were only warped on the sides, but were warped enough to allow fuel to leak, despite a pretty thick (1/8"?) gasket. The front and rear sides of the bowls did not seem to be warped or at least not as much.

​Could you describe why a warped carb would warp the bowls to cause them to leak?

I can't -- other than dissimilar materials. Maybe cold fuel entering the bowl makes the situation worse due to contraction/expansion issues. Sounds suspiciously like a design or manufacturing flaw, though, particularly if sides are invariably where the leaks appear.

A criss-cross pattern is probably important, then final torque in a circular pattern. Probably a good candidate for gasket sealer as well.

 

[racerone]

Bowls " bend " over time because screws are tightened too much.---The rubber gaskets squeeze out easily.

 

[jakedaawg]

Just my .02 cents. I have had much good fortune with a plate of glass, Emory cloth, finishing compound, gasket, and gel seal on both sides of gasket with bowl screws slightly more than finger tight. I use a little stubby ratchet and barely tighten them.

 

[Chris1956]

Just to be clear, my motor runs perfectly. However, when the motor is trimmed for cruising speed, all the carb bowls leak fuel.

I think the carb bodies are the same hard plastic as the bowls

 

[oldboat1]

Dunno, Chris -- plastic on plastic carb likely mounted on an aluminum throttle body? Still seems like there might somehow be warping due to heat. Sounds like light, even retorque with a good gasket and sealer might be a necessary ongoing fix -- maybe along with periodic cleaning and resurfacing.

 

[gahunter706]

Well it looks like the carbs might not need new bowls after all, at least for now. Last time I had ran the boat was in mid November, and the bowls were warped just enough that a little gas would seep out when I pumped the bulb, and the motor would stumble a little at full throttle. I figured they had got worse since then, which is why I started this thread, but to my surprise when I looked at the motor last Friday the carbs didn't leak any when I pumped the bulb. Took the boat out Saturday and Sunday nights and it ran flawlessly.