1988 Johnson 90 V4 VRO Broken Tube on Fixture

Repair or modification of Boston Whaler boats, their engines, trailers, and gear
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1988 Johnson 90 V4 VRO Broken Tube on Fixture

Postby Wyowanderer » Thu Jul 11, 2019 5:15 pm

Fig. 1. Broken tube coming from fixture on engine.
B0C36787-1531-492B-823F-AE16AEE20E15.jpeg (11.93 KiB) Viewed 3188 times
In the process of cleaning the carburetors on my J90TLCCA, I found a broken tube coming out of the fixture seen above in Figure 1. I have researched everywhere and can not find out what type of fixture this is.

Q1: Is [the fixture] just a vent?

Q2: Should the hose attach to something?

Thank you for your assistance.

Crusty the Clam
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Location: Austin, Texas

Re: 1988 Johnson V4 VRO 90hp

Postby Crusty the Clam » Thu Jul 11, 2019 8:48 pm

On the intake manifold parts diagram, could that broken tube be Part 38 - a cut to length "house" (odd name) associated with the "air silencer"? If so, then according to the diagram, part 43, a nipple, looks like it's supposed to be on the end of the "house".

Diagram https://www.crowleymarine.com/johnson-evinrude/parts/46498.cfm?mdl=FMV0LR

Nipple Part https://www.crowleymarine.com/parts/13037.cfm

What the "house" does and whether it is important to have a nipple on the end, I have no idea. Nor how long it should be per the meager instruction to "cut to length" that shows up when you click on 38 in the diagram.

EDIT to add: The marineengine.com website part listing says cut the "house" to 6.5 inches. Not clickable so scroll down to part 38.

ME.com https://www.marineengine.com/parts/johnson-evinrude-parts.php?year=1988&hp=90&model=J90TLCCA&manufacturer=Johnson&section=Intake+Manifold

I'd look at the Service Manual if you have one to see what it says about it.

EDIT #2 to add: only slightly less trustworthy than Wikipedia, I conducted a google search for johnson V4 air silencer. Despite the name, *I think* I gleaned that its function is in control of air flow to the carbs. That sounds important in ensuring you've got the correct air/fuel ratio to the carbs... hopefully persons with true knowledge will share.

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Re: 1988 Johnson 90 V4 VRO Broken Tube on Fixture

Postby jimh » Fri Jul 12, 2019 10:10 am

The air silencer on an OMC two-stroke-power-cycle engine usually has a drain outlet located at the bottom. Any fuel that spills from the carburetors collects there. A hose usually routes this oil into the oil recirculating system, which is a series of hoses that routes oil back into the crankcase on each cylinder. The details can be found in the service manual.

In Figure 1, I don’t see a broken hose. I see a hose fitting that looks like its associated hose has fallen off. There should be nearby a hose that is not connected to anything. That hose probably came off the fitting. I do not see “the hose” in the illustration.

To work on your outboard you will need the service manual to do the work properly, otherwise you will be stumbling around poking at components and guessing.

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Joined: Fri Oct 09, 2015 12:25 pm
Location: Michigan, Lower Peninsula

Re: 1988 Johnson 90 V4 VRO Broken Tube on Fixture

Postby jimh » Mon Jul 15, 2019 9:14 am

The component called an air silencer functions to diffuse and reduce the noise of the air being sucked into the carburetors. If the engine were run without the air silencer, the engine noise would be louder.

Because a carburetor can spill fuel from its throat when tipped 90-degrees, the air silencer acts as a catch basin to hold the fuel, and there often is a drain tube that tries to recirculate the fuel. The spills may occur then an outboard engine is tilted to a fully-up position, as occurs when the operator wants to get the gear case clear of the water.