Fuel Leak around Carburetor Bank on 1986 Johnson 150 HP Outboard with VRO

[Terrapin]

I have a fuel leak that seems to be at it's worse after I turn off the engine. I am having a difficult time identifying the source of the leak. It seems to be coming from the carburetor bank and related fuel and recirc hoses. I rebuilt the carbs approximately 4 years ago and the engine runs great.

1. Are there any typical leak sources prevalent in these triple carb outboards?
2. Does anyone have any suggestions/tricks to help finding the leak? For example, should I spray the carb and hose area down with simple green to remove existing fuel/oil and then run engine to look for the leak? I also thought I read something about dusting the area with baby powder to help identify the source.

I'm looking for some help prior to jumping into this search. Thanks in advance for your help.

 

[Joe Reeves]

Am I correct in assuming that although you worked on the carburetors 4 years ago, this fuel leakage problem is just now an existing problem... OR... has it been a problem all along?

Have you have fuel tank work of some kind performed at some point... and this problem popped up shortly thereafter?

With the carburetor face plate removed so that you can observe the carburetor setup completely, and with the engine in a running position (not tilted & not running), and pumping up the fuel primer bulb to its hardest condition... does any amount of fuel leak from anywhere?

 

[Terrapin]

Joe, Thanks for replying and sorry for the delay in getting back to you. I appreciate your patience with the following long post.

The fuel oil leak started about a year ago. To clarify, approximately four or five years ago I rebuilt the three carburetors with OEM components/rebuild kits. At that time, I replaced all of the fuel hoses from engine inlet to the carburetors. In addition, I replaced all of the recirc hoses. I also replaced the inline plastic fuel filter, the vertically oriented plastic carburetor feed pipe, and purchased the custom formed fuel lines where available. The VRO was replaced about 10 years ago. The goal was to update the fuel lines to ensure they were ethanol resistant.

I utilized the clamping arrangement suggested by the OEM parts list and manual. Mainly the plastic ratchet lock clamps and the cable style clamps (OEM style). The recirc hoses do not have any clamps on them as I read somewhere that they are not needed. I do question the OEM clamping solution and I am considering pulling the carbs and replacing the existing clamps with properly sized Oetiker clamps.

Yesterday, I removed the air silencer cover. It is important to note that fuel oil did drain out of this area upon cover removal, and this was done prior to waking the engine from last fall’s winterization and fogging. I ran stranded wire thru the silencer base drain hole to ensure it was open. I cleaned the silencer base and pumped up the fuel primer bulb hard. I could feel and hear the carb float bowls filling and then stop filling when doing this. I pressurized the system multiple times and did not see any leaks at the carb air inlet area or could not detect a severe leak elsewhere in the fuel lines. I re-torqued the silencer base to OEM specs and also ensured the carb nuts were tight. I backed the boat down the boat ramp and started the engine (silencer cover and engine cover off) to burn off the fogging oil. The engine ran well, but I did witness oil leaking in the usual location which is down the back side of the swivel bracket and down the lower unit. I can’t see any major leak under the engine cover or elsewhere that supports this amount of fuel/oil leakage.

A few years ago I pulled the fuel tank inspection cover (approx. 6 inch diameter) made a new gasket, reinstalled the cover and installed new fuel lines to the Racor filter and engine. I can’t relate the leaks to this service work to the best of my knowledge. Boat is a 1986 Boston Whaler Outrage 18.

Any investigative ideas are welcome.

 

[Joe Reeves]

1986 150 Johnson

Yeah, you may be running a little late... but you are thorough! I read your reply over a couple times or so as I do have a careless habit of skipping over things that turn out to be important. However... you have covered all bases in your quest to find that leak and I find no problems in your listing.
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The only area I might disagree with pertains to the clamps of which I must admit... I wouldn't recognize one from the other just by their names... you would really need to spell it out for me as distinct descriptions. The difference between what I'd call OMC Tie Straps and regular hardware store tie straps is that the OMC straps have a curved inside locking end that matches the curve of the hose... regular tie straps do not. However, either do the job quite well, and if any leakage occurs with either, the hose is to blame..
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However, pertaining to the work you've done, I am absolutely satisfied that nothing leaks in that area and will not for quite some time.
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There are two areas you've not thought of as follows;

The driveshaft tube.... If the top portion of the water pump is not sealed... AND... the exhaust tuning tube, where it seals to the lower unit happened to be hit & cut or flipped when the lower unit was reinstalled... that would allow black sooty exhaust shoot up the driveshaft tube, into the top motor mount area which could then run down the area you mention. However I don't think this is your problem as it is very unlikely.

Your problem, I feel, is that originally the powerhead base gasket, the gasket between the powerhead and the adapter plate upon which the powerhead sits, is a flimsy thin thing, about the thickness of toilet paper, but has been the norm since the V6 came into existence... and has worked fine UNTIL the 1986 150hp model came upon the scene.

It was with your model engine that it became known that the thin strand of gasket that borders the hot exhaust blast chamber from the top motor mount area would fail which allowed that hot, oily, fuel soaked mixture to blow into the top motor mount area with the result being.... yep, you guessed it... one hellava mess running down the outside portion of the engine.

But OMC upgraded that gasket to a super thick one that'll last forever (almost).

Your gasket = 323212..... New improved gasket = 333658
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If that doesn't cure the leak, I'll wait for another member to come up with the answer.

 

[Terrapin]

Joe, you may be on to something with the powerhead gasket. I will add that the leakage I see going down the lower unit seems to be a fairly clean fuel oil mixture. It appears to be a greeninsh color. I am running the XD100 OMC oil in an attempt to reduce exhaust smoke, but the XD100 is light brown in color I believe. The point I am trying to make is it isn't black or a burned exhaust color. Would the light greenish color fuel oil mixture seem correct for your powerhead gasket failure?

My 1986 Johnson 150 HP model number is J150TXCDC. Can you double check the OEM part number and replacement part number? I am not seeing the gasket p/n 323212 or 333658 in the OEM parts list.

Lastly, how hard of a job would this be?

Thanks,
Vince

 

[Joe Reeves]

Joe, you may be on to something with the powerhead gasket. I will add that the leakage I see going down the lower unit seems to be a fairly clean fuel oil mixture. It appears to be a greenish color. I am running the XD100 OMC oil in an attempt to reduce exhaust smoke, but the XD100 is light brown in color I believe. The point I am trying to make is it isn't black or a burned exhaust color. Would the light greenish color fuel oil mixture seem correct for your powerhead gasket failure?

My 1986 Johnson 150 HP model number is J150TXCDC. Can you double check the OEM part number and replacement part number? I am not seeing the gasket p/n 323212 or 333658 in the OEM parts list.

Lastly, how hard of a job would this be? Thanks, Vince

Vince... I can't comment on the coloration as what usually gets blown past that gasket hits soot covered walls and God knows what all. What is taking place with your engine may have nothing to do with that powerhead gasket... BUT... it is the most likely culprit since you have been unable to find leakage elsewhere.

I, just this minute, double checked the model number above, having it imprinted on the OMC parts manual in front of me, and what I've always referred to as the Powerhead Base Gasket is listed as 323212. The improved part number of 333658 wouldn't be mentioned of course as of that date (it's just something we know about) and didn't show up in the part manuals until 1988.

I assume that you couldn't find part #323212 or 333658 as 323212 was superseded back in 1986 and eventually dropped and I just noticed that 333658 was recently superseded up to gasket part number 0335503 for some reason. I still have two of the 333658 gaskets in my remaining stock. I'll have to buy a 0335503 gasket to see what the difference is... probably nothing more than needing to stick that "0" in front of it for computer compatibility.

Bottom line... If you decide to.replace that gasket, it's now part #0335503.

How hard a job is it? Normally it's about a 3 to 4 hour job which includes run out, adjustments ,etc... however, have one bolt break, or encounter a jammed corroded bolt... a hour or two could easily be added.

 

[w2much]

One note to add. Unless you are Joe that Normal 3 to 4 hour may be a day or so. And that bolt hour or two ? In my dreams.

 

[Terrapin]

Joe, sorry for the delay again. I just returned from a week on the Chesapeake Bay and used my boat daily.

Although the "greenish color" fuel oil mixture seems to start that way after lower unit clean up, after a week of running it seems to become blackish possibly from the exhaust leak contributing to the leakage.

You are certainly a wealth of information regarding the OMC part numbers and I will make note of the need to use OMC p/n 0335503. Are there any other components I should replace when replacing this powerhead gasket?

I don't plan on jumping into this at this time as I prefer to just enjoy the boat during the summer months. However, I am tempted to give it a try. Albeit, with a lot of fear of stuck bolts. And yes, 3 to 4 hours for you, but much more for me with my limited experience. A year or two ago I had great success removing my heads and replacing the seriously distorted water deflectors. The job went well and I most likely have to thank the previous mechanic that used the correct OMC sealant on the bolts (if in fact anyone else was in there). The bolts came out nicely to my surprise.

Thanks again,
Vince

 

[oldboat1]

Isn't that motor equipped with the plastic carb bowls that tend to warp? You might do a search here on iBoats to explore that. If the leaking seems to come from one of the carbs, you might switch bowls with another of the carbs and see if the leaking problem follows. It's possible, I think, that the leaking might mysteriously stop.

 

[Joe Reeves]

Isn't that motor equipped with the plastic carb bowls that tend to warp?

No... That model, 1986 150hp, incorporates all aluminum carburetors.

 

[oldboat1]

Thanks, Joe. :thumb: (Terrapin -- sorry. Bad lead.)

 

[flyingscott]

Is.the airbox gasket in good condition? Is the reclaim hose from the airbox attached?

 

[Terrapin]

Yes, the airbox gasket was replaced and the reclaim hose is attached. However, I did not use any hose clamps on the reclaim hose ends.

Joe is correct, I checked the carbs and the bowls are not plastic.

Thanks for the comments