Johnson QD fuel consumption

[fleetwin]

OK, lost the first post that took me ten minutes to type out….No comment….

Anyway, I don’t think there is a way of “recapturing” the excess fuel/oil that would otherwise drain down and out of this engine, unlike the larger engines with the external drain port cover.  I suppose it is possible that the little drain/reed is partially stuck open on the back side (closest to pistons), of the reed plate.  Not tough to check on this engine, the gaskets should have been installed dry.  I suppose it would be possible to temporarily plug off the little drain passage that leads down and out of the crankcase, but the word temporary is key here.  Don’t stick anything in there that can’t be easily removed for this “experiment”.  Unfortunately, with the passage plugged off, my guess is that the engine will load up at idle and have to be “blown out” frequently to expel the stuff that puddles up in the crankcase at low speeds.  Needless to say, all this is counter productive if you use the engine to fish/troll.

1 user thanked author for this post.

Fastwin18

[Fastwin18]

Thank you for your elaborate answer. I’ll leave it as is for now. I’m curious to see what it will do the next trip, and what the consumption will be under load. I will keep you posted!

[mike n]

i have a qd19 also. it runs great.  i have never checked fuel consumption, but i do have EXCESSIVE raw fuel behind boat when running slow. i put a new set of rings and had no change. i changed the fuel dump valve from a parts engine and even tried another carburetor . it never changed? its been a mystery. my qd17 and qd 20 have very little trace of raw fuel dumping???

mn

[Phil Budne]

Here’s an article on catching the crankcase bleeder output on a 1954 5.5hp: https://www.duckworksmagazine.com/06/columns/rob/maib1.htm

 

http://www.omc-boats.org
http://www.aerocraft-boats.org

[jeff-register]

Phil,

I like the “redirect” of waste oil. Simple solution to save the polution. Two strokes make much more power & are so much lighter. Cleaning them up never hurt!

I’m always learning more here. Mercury 6 cylinder motors already have crankcase drains with external drain hoses. How simple just to add a “catch” container to clean them up!

[Phil Budne]

I also have some memory of reading how someone modified a later (1970’s 22ci 18 or 25?) where the crankcase drain was routed into the exhaust manifold/bypass rather than dump it completely unburned.

And I also remember seeing a chapter local newsletter about doing capture on a 1950’s 25, where drain(s?) are under a plate at the front of the engine…

http://www.omc-boats.org
http://www.aerocraft-boats.org

[rudderless]

A lot of the issue is throttle cam shape.  A lot of older motors have a lot of  throttle with respect to timing advance.  Not recommending this but I have slowed the throttle ramp up by reshaping the throttle cam.   The motor at same output will have less throttle opening with more timing.   Keep in mind that might lower the effective lubrication at lower speeds as less fuel will be consumed.

[Finn Freeman]

Phil Budne wrote:

I also have some memory of reading how someone modified a later (1970’s 22ci 18 or 25?) where the crankcase drain was routed into the exhaust manifold/bypass rather than dump it completely unburned.

And I also remember seeing a chapter local newsletter about doing capture on a 1950’s 25, where drain(s?) are under a plate at the front of the engine…

Here is that chapter article I think you were talking about. Starts on page 4

http://www.ultimate.com/phil/boat/propnutz-2012-09.pdf

[crosbyman]

nice explicit article    1/20 or 5%  fuel oil recovered and recycled….fish like it 🙂

Joining AOMCI has priviledges 🙂

[fleetwin]

Again, the larger engine pictured in that article has the external cover with the drain valves inside.  The QD models don’t have this style cover set up.  The drain valve is on the reed plate and directs the excess puddled fuel/oil to an internal passage inside the front crankcase cover that directs the puddled fuel down into the exhaust housing.  There is no easy way to redirect the puddled fuel/oil on the QD series powerheads like there is on the larger engine pictured in the article.  I suppose you could remove the powerhead, then drill a hole perpendicular to the tiny drain passage, then adding the nipple to recapture the excess puddled fuel, while blocking off the actual vertical drain hole in the front crankcase cover.  But, this would be quite the delicate procedure to get everything right for this experiment.

These QD series engined don’t have any of the “recirc features/lines” like those used in the 22CI engines in the early 70s either.

[Author]

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