Mercury 90 fuel leak

[nokiddin]

I have a 1984 (according to serial) Merc 90 hp inline 6 2 stroke. Yesterday on the water, it wouldn't idle without the fast idle on or without a bit of throttle in gear, usually when i popped it in gear it would stall out. Once it was goin, it seemed to do not too bad. I also noticed I could smell gas around the engine. I should mention that i had a brain fart and started the motor before it was in the water, probably ran for 5-10 seconds.

Today, I looked at it and found that the line that goes from the choke solenoid to the top carb bowl was split where it fits onto the carb fitting. Was definitely leaking. Could this have been sucking air in? So I trimmed the line and put it on again. No more leaking.

I started it in a tank and idled it for about 10 min. The water jacket was cool to touch all this time, and it idled fine now.

However, I can tell there is still fuel dripping from the bottom of the float bowl at the bottom carb. I can see fuel coating the whole throttle linkage all the way up to where it comes from the top carb. Any idea what could be making fuel leak from there?

Also, any way to test my choke solenoid? It clicks when the key is pushed in and I can push the on the bottom of it and there is movement, but this doesn't move when the key is pushed in. ( not sure if this is supposed to move)

The way it was acting sort of reminded me of my snowmobile when one choke was stuck open.

Thanks for any help!

 

[canoemang]

Re: Mercury 90 fuel leak

The choke solenoid is an enricher valve. The click you hear is the valve being opened and gas being fed from the top carb to the cylinders. It would leak bad if it the upper hose between the upper carb and it were cracked.

To test is remove the bottom fuel line and push key in, it should click and dump fuel.

As for the leak, sounds like it is time to change your needle and seats if it is leaking from the throat (front) of the carb.

 

[nokiddin]

Re: Mercury 90 fuel leak

Will have to check the choke out. Could it get stuck open? dumping fuel all the time?

The leak from the carb doesn't seem to come out the front of the carb, but it seems to come from somewhere near where the throttle linkage (that connects all the carb's throttle controls) attachs to the carb. There is a spring in this area on the linkage that has fuel on it, and from there it runs all the way down the linkage to the bottom of the bottom carb.

 

[nokiddin]

Re: Mercury 90 fuel leak

Just wondering if the split line on the float bowl of the top carb could have caused the engine to not be able to idle? Could it have been sucking air or something? Just want to know if that seems to be a sufficient cause of not being able to idle

 

[nokiddin]

Re: Mercury 90 fuel leak

No thoughts guys?

Tonight I ran my motor in the tank after drying all the leaked fuel off the carbs, couldn't seem to make that leak happen again that went all the way down the throttle shafts from the top carb to the bottom. However I did locate a leak from the bottom of the bottom carb. The carbs are side bowl. This leak seems to be coming from either the main fuel jet channel plug screw, or from the main nozzle plug screw. the fuel definitely drips from the plug screw on the bottom, but it gets a little wet above this too. I tried tightening both of these (very difficult to get to the bottom of the bottom carb) but didn't stop the leak.

Should I change the gasket on the main fuel jet channel plug screw? I don't think there is a gasket on the screw on the bottom.

Any other ideas where it could come from? I pulled out the plug screw on the side and gas leaked out, i replaced it, it leaked for a bit then stopped. I pumped the primer bulb a bit and the leak started again.

If I pull the carb off to work on it, do I have to change all the gaskets where the carb is mounted?

 

[canoemang]

Re: Mercury 90 fuel leak

There is no gasket under the bottom screw, you have to remove it and loctite it or pipe dope it.

It is good practice to replace the gasket after removal and since your doing it why not do it rite. Check floats and float height and jets, all of the above may help with idle. Do a linc n sync after reassembly.

did you test the enricher system?

 

[nokiddin]

Re: Mercury 90 fuel leak

I didn't test the enricher system, but last time I started it, I pushed the key in a few times, cranked it, it almost went, pushed the key twice more and she fired up and idled. Didn't use any fast idle. I haven't had this boat long but every other time I tried to start since I've had it, I couldn't get it started without using the fast idle. It seems the enricher must be working now since I fixed the split fuel line if it started like that.

Is there any other place fuel could be leaking near the bottom of the carb? When I dry it off it gets damp by those plugs i mentioned above, So i assume one of them is the culprit, but just wanted to make sure there's nothin else to check while the carb is off.

 

[Wingedwheel]

Re: Mercury 90 fuel leak

You say you haven't had the boat that long so do you know the last time you or the PO may have done any maintenance,(carb kits) or work on the fuel system. the Ethanol in the gas dissolves the inside of the fuel lines and it can cause problems as well. it may be a good idea just to pull your carbs and clean them, and check the gaskets and seals. The leak may be something as simple as a sticking float.

 

[redjmp]

Re: Mercury 90 fuel leak

Just wondering if the split line on the float bowl of the top carb could have caused the engine to not be able to idle? Could it have been sucking air or something? Just want to know if that seems to be a sufficient cause of not being able to idle

The enricher valve dumps fuel from the top bowl staight into the crankcase. A split in that line means that the engine can suck in extra air and cause a lean condition and hard idling.

 

[nokiddin]

Re: Mercury 90 fuel leak

I talked to the previous owner and he said he never did the carbs and never did have any carb trouble. He had the boat for only a couple years I think. I do know he always used premium and so do I. I think I might try the boat out again now that I fixed the split line because it idles nicely now at home. Don't really wanna do a carb job in the middle of the season if she runs good now, however I would like to find that leak.

If a float is stuck, where would the fuel usually leak from?

 

[nokiddin]

Re: Mercury 90 fuel leak

Update on the leak.

I haven't seen the fuel coming down the whole throttle shaft since when I first posted about this issue.

However, for the fuel dripping off the bottom of the bottom carb, the fix was to pull the carb off and I put some loctite on the jet plug that goes in from the bottom of the carb. Seems to have taken care of the leak.

 

[jarwhaler]

Re: Mercury 90 fuel leak

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