Yanmar1GM Running backwards!

stephennoble

stephennoble

Active Member
Joined
2 Oct 2014
Messages
45
Location
Bournemouth
Visit site
I went to give my boat a Christmas hug today and take her sails off. Thought I would run the engine for a bit to top up the batteries and move the oil about. I tend to start her decompressed and then drop the leaver. It was quite cold and after I stopped pushing the starter motor button she made a few normal combustions slowly to get going. Anyone with these engines will probably still be with me here. I was watching the motor and she was not quite taking and on the upward combustion stroke didn't quite make it and went into reverse combustion. The compartment started to fill with fumes but quickly she was stopped. Restarted and all is well, she ran happily for half an hour quite normally and sucked the fumes back through the air filter!:cool:

For those who are more mechanically minded than me the question is...What if any damage can be done if this happens?

And happy Christmas to you all.:encouragement:
 
From my perspective there are 3 issues. Cooling water flow, alternator/battery charging, fuel pump timing. As you found the fuel pump timing while obviously out will allow the engine to run but undoubtedly if you tried to apply power etc it wouldn't run correctly. In the short term (a few seconds) the cooling water flow won't matter but after that you risk running the pump dry as you will be sucking air back through the exhaust rather than water. Finally the alternator running backwards should do no harm but somebody with better electrical knowledge than me should be able to confirm this or otherwise. In short a few seconds shouldn't hurt but any longer should be avoided.

Yoda
 
Mine did it occasionally on y last boat, I found starting with almost full throttle stopped it. As to damage, for a few seconds I can't see any damage being done.
 
Lack of oil pressure when running backwards would be the engine killer. A few seconds should not be a problem.
 
On some older motorbikes there was a lever under the seat which retarded the ignition for easier starting (and safer ankles). You could then bump start them backwards. Having done that you could sit on a mate's machine and then watch him try to go when he took over..........

my bantam never started backwards but never having had a two stroke before when it was running badly i thought it might be a sticking valve and was confused over how to access the valves and check.............
 
Been there, done that (but with a warm engine and hand starting). You will probably need a new foam air filter - it doesn't like hot gases. Some bits of it may remain in the casing, the rest may have helped to fuel the engine once it was going the right way.
 
And the Messerschmidt Bubble Car did not have reverse gear - one stoppped the engine, turned a switch over which reversed the polarity, started it up and the engine then ran backwards.
Hence one could us all the gears, but with the engine running backwards one could travel as fast reversing as forwards.
 
djyacht said:
And the Messerschmidt Bubble Car did not have reverse gear - one stoppped the engine, turned a switch over which reversed the polarity, started it up and the engine then ran backwards.
Hence one could us all the gears, but with the engine running backwards one could travel as fast reversing as forwards.
Click to expand...

Same with the Daf cone/belt transmission. Our Daf Marathon coupe could(in theory) exceed 90mph. In reverse.
 
You must log in or register to reply here.

Other threads that may be of interest

UK-WOOZY
Autoterm 4kw heater was blowing smoke out into the cabins
2
Replies
25
Views
945
Babylon
B

Share this page

Top