Johnson 40 VRO Model Year; Stall at Idle

Repair or modification of Boston Whaler boats, their engines, trailers, and gear
PriorEngagement
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Johnson 40 VRO Model Year; Stall at Idle

Postby PriorEngagement » Mon Jun 22, 2020 6:50 pm

I just purchased a 13-footer with a Johnson 40-HP VRO engine. I am having trouble determining the engine model year. Help me determine the engine model year from the Engine ID Plate:
MOD No. J40ECUD
SER No. G 7417642

The engine starts and runs. When I push the idle [speed] control lever all the way down the engine stalls.

What is a starting point to diagnose the cause of the stalling?

To remedy the stalling I plan to replace the spark plugs, and put fresh gasoline fuel in the fuel tank, pre-mixed with oil.

Thanks,
Josh

biggiefl
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Re: Help with Johnson 40 VRO

Postby biggiefl » Tue Jun 23, 2020 12:18 pm

The model year of the engine is 1987.

To change spark plugs and fresh gasoline is always a good idea.

An engine that won't idle is usually due to a clogging in the idle circuit in the carburetors. There is a small jet that supplies fuel for idling.

Is the engine running on both cylinders?

Have you measured the cylinder pressure?
On my 24th Whaler. Currently in the stable: 86 18' Outrage, 81 13' Sport(original owner), 87 11' Sport, 69 Squall(for sale cheap).

acg123
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Re: Help with Johnson 40 VRO

Postby acg123 » Wed Jun 24, 2020 11:24 pm

I had the same engine, and it stalled at idle. [The cause of the stall at idle] usually came from the carburetors not being sealed well and getting air leaking in when pulling fuel.

The remedy is to take apart the carburetor, and make sure they are sealed well when put back together. I would sand them very lightly on a flat surface. Also, use fuel treatment and don’t use carburetor cleaner. Good luck.

biggiefl
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Re: Help with Johnson 40 VRO

Postby biggiefl » Thu Jun 25, 2020 10:01 am

If you are cleaning a carburetor you use carburetor cleaner. If you are adding stuff to your fuel, use a fuel treatment.

I have never had to sand a carb, majority of times I reuse the gaskets if they did not tear.

Do not run it unless you want to risk doing damage. A lean carb means KABOOM.
On my 24th Whaler. Currently in the stable: 86 18' Outrage, 81 13' Sport(original owner), 87 11' Sport, 69 Squall(for sale cheap).

Don SSDD
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Location: Nova Scotia

Re: Help with Johnson 40 VRO

Postby Don SSDD » Fri Jun 26, 2020 6:13 am

How old are the fuel lines?

If the fuel hoses are old they may be leaking air. Replace the fuel hose from tank to outboard.

Does the engine have good power when running the boat, but only stalls at idle problem?

If so, I’d change the spark plugs, and add SeaFoam or similar to your fuel and take it for a trip for 30-minutes at at half-throttle to two-thirds-throttle to get the fuel with additive through the fuel system.
After doing that, see if the idle changes.

If not, very thoroughly clean the carburetors.

If it has poor power above idle, clean the carburetors and do a compression check.
1986 Outrage 18 with 2001 Honda 130 HP
Former Owner 1991 Guardian 19 with 1994 Evinrude V4 140HP
Former owner 1987 Montauk with 1998 Mercury 90HP
Nova Scotia

jimh
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Re: Johnson 40 VRO Model Year; Stall at Idle

Postby jimh » Fri Jun 26, 2020 8:00 am

PriorEngagement wrote:Help me determine the engine model year from the Engine ID Plate: MOD No. J40ECUD

Evinrude and Johnson engine features and model year can be deduced from their model descriptor. See

http://continuouswave.com/whaler/refere ... Codes.html

J40ECUD decodes as

J = Johnson
40 = horsepower
E = electric start with remote
CU = 87 or 1987
D = model run suffix

jimh
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Re: Johnson 40 VRO Model Year; Stall at Idle

Postby jimh » Sat Jun 27, 2020 10:31 am

PriorEngagement wrote:What is a starting point to diagnose the cause of the stalling?

A brief general procedure for assessing an outboard engine for proper running is given at

Assessing Used Outboard Motors
http://continuouswave.com/whaler/refere ... Check.html

PriorEngagement
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Joined: Mon Jun 22, 2020 6:48 pm

Re: Johnson 40 VRO Model Year; Stall at Idle

Postby PriorEngagement » Mon Jul 06, 2020 10:32 am

FOLLOW-UP

I rebuilt both carburetors, changed the fuel tank, fuel lines, fuel filter, and spark plugs.

Because the boat was running great I thought that did the trick.

After about five gallons of fuel was consumed the [1987 JOHNSON 40-HP engine] resumed its rough running.

The boat ran great in a ten minute ride. After the engine sat for an hour, we were headed back it, and the Johnson 40-HP engine was running rough only on one cylinder. At first I could feel the other cylinder kicking in for a second or two; now [the engine or the second cylinder] is totally dead.

Tell me what to check.

[Could the remedy] possibly [be found in ] a new ignition?

Thanks,
Josh

biggiefl
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Re: Johnson 40 VRO Model Year; Stall at Idle

Postby biggiefl » Mon Jul 06, 2020 11:07 am

Check coils. swap them and see if dead cylinder changes. Very common. If that is not the problem chances are the CDI is toast but usually that gives weak or low spark to both cyls. My bet is one of the coils.
On my 24th Whaler. Currently in the stable: 86 18' Outrage, 81 13' Sport(original owner), 87 11' Sport, 69 Squall(for sale cheap).

jimh
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Re: Johnson 40 VRO Model Year; Stall at Idle

Postby jimh » Mon Jul 20, 2020 8:26 am

An engine running problem that occurs after a hot engine has been siting or heat-soaking can be related to electronic ignition components. Often electronic devices fail after their operating temperature rises. In OMC jargon the ignition spark controller is called a Power Pack.

To check for spark use an in-line spark gap test tool.