Johnson QD fuel consumption

[jeff-register]

Don,

What is different on crankcase drains from older to newer models?

Jeff

1 user thanked author for this post.

Fastwin18

[Fastwin18]

Good point Jeff, you’ve got me thinking!
What I failed to mention is that I converted this motor to a single fuel line, see the images below. The air supply to the fuel tank was blocked with JB weld, and it from what I can tell it is not leaking any fuel. Just to make sure I will connect a hose, stick the other end in a bottle and run the engine for a while to make sure it is not leaking at that spot. If it is fuel should be visible in the bottle.

[Fastwin18]

Happy to confirm it’s dry. It’s also air tight, no bubbles are coming from the hose with the other end submerged.

[Fastwin18]

Just tightened all hose clamps to be sure. One seemed a bit loose. It was on  the pressure side of the pump, so that could have been a factor. Any spilled unburnt fuel now can only be coming from the crank case.

[crosbyman]

you can always modify the crankcase purge to dump crankcase juices in a bottle …  instead of down the exhaust housing  the recovered fuel-oil can be  put back in the  fuel tank at the end of the day and it will help the fish. 🙂

 

 

Joining AOMCI has priviledges 🙂

[Fastwin18]

crosbyman wrote:

you can always modify the crankcase purge to dump crankcase juices in a bottle …  instead of down the exhaust housing  the recovered fuel-oil can be  put back in the  fuel tank at the end of the day and it will help the fish. 🙂

 

 

Would that be done by simply unblocking the old air supply line again and connect a hose? If so that would be tempting.

[kerry]

General rule of thumb (not carved into stone) is an outboard will consume the most fuel (1) pushing the boat off plane above trolling speed, (2) pushing the boat to plane, and (3) full throttle. Trolling JUST off idle and planing at around 3/4 throttle are usually the most efficient.

If you have too many, AND not enough, you're a collector.

[crosbyman]

the crankcase  drain channels  diverts crankcase juice to the purge valve and out the back end… not certain  using the air nipple would do it properly since  it sits above the purge valve.   The  resulting loss of  pressure normally built up in a two line tank  would also  reduce crankcase pressure possibly affecting engine performance …which is why we plug it  in the first place .

I tried  finding a utube on it and did a search here to no avail.  May have been an OUTBOARDER article  some time ago ??   can’t recall.  it basically involved blocking the purge drain   and adapting a cover/nipple on the purge  then sending juices back to a bottle.. juices build up at lower speed … at high rpms  the  fuel oil mix  does not accumulate so much being  pushed  into the cylinders.

 

up to you… depending on how bad things are… did you try adjusting  the carb .  both cylinders  working  properly all at speeds ???

Joining AOMCI has priviledges 🙂

[Fastwin18]

kerry wrote:

General rule of thumb (not carved into stone) is an outboard will consume the most fuel (1) pushing the boat off plane above trolling speed, (2) pushing the boat to plane, and (3) full throttle. Trolling JUST off idle and planing at around 3/4 throttle are usually the most efficient.

That’s what I thought, which why I was surprised about the gallon/hour rate when trolling. I was expected roughly half of that, which would mean the other half is wasted by bleeding the crank case? Seems rather excessive to me.

[Fastwin18]

crosbyman wrote:

the crankcase  drain channels  diverts crankcase juice to the purge valve and out the back end… not certain  using the air nipple would do it properly since  it sits above the purge valve.   The  resulting loss of  pressure normally built up in a two line tank  would also  reduce crankcase pressure possibly affecting engine performance …which is why we plug it  in the first place .

I tried  finding a utube on it and did a search here to no avail.  May have been an OUTBOARDER article  some time ago ??   can’t recall.  it basically involved blocking the purge drain   and adapting a cover/nipple on the purge  then sending juices back to a bottle.. juices build up at lower speed … at high rpms  the  fuel oil mix  does not accumulate so much being  pushed  into the cylinders.

 

up to you… depending on how bad things are… did you try adjusting  the carb .  both cylinders  working  properly all at speeds ???

Yes, both cylinders working properly and the engine runs smooth. Both sparks plugs have the same color.
I’ll have another go this weekend and see if adjusting the carburetor helps.

[Author]

Posts