Universal 5425 stopping

[Shamwari]

The owner's manual for this motor states that you may cause "serious damage" to the exhaust valve if you stop yor motor with the compression release. Does anyone know exactly what it is supposed to do to the engine?

My motor was stopped this way for 5 times or so, and I want to know what to look for.

Thanks
John Gleadle

 

[Emerald]

In general, the compression releases I've seen have held open the valve(s). If the valve were being held open by the decompression lever, and were then actuated, you can envision things trying to bend etc. as the valve doesn't move when rocker, push rod etc. do move.

 

[Shamwari]

I know that's what might happen if there isn't enough space, but I wouldn't have designed a motor to destroy a valve under emergency shutdown. I'm hoping someone has first hand experience having removed the head. The decompression shaft only opens the valves very slightly and I thought the problem might be letting very hot exhaust escape past the seats burning the seats or valves.
I took the valve cover off and the valve seems to be operating properly.

 

[Emerald]

I think of the decompression levers more for emergency starting, even though I know that they also serve for emergency stopping. Now, having said that, we should probably toss out my prior post regarding clearances.

So, flipping open the handy 3GM30F Yanmar shop manual, the following caution on stopping from section 13-11 2-4.2, "1) Do not stop the engine with the decompression lever. If the engine is stopped with the decompression lever, fuel will remain in the combustion chamber and abnormal combustion will occur when the engine is started again, perhaps damaging the engine."

My 2QM15 manual has the same passage, verbatim (but chapter 12 ).

So, even though this is from the Yanmar manual, not the Universal manual, perhaps it's the answer we're looking for

 

[Shamwari]

Thanks Emerald
Thats just the info I was looking for. I started it after and it wasn't hydro locked so I guess it's all right.

 

[Sean Engle]

From Glyn Judson...

This from Glyn Judson - I'm only saving him the hassle of re-keying all of this...:nerd: :

David,
Re: the thread on using the compression release for starting, on several occasions when I was resolving bad batteries and chargers, I've found myself unable to start the engine in one case, attempting to leave Catalina Island after four days stay.

The trick I used and you can too now that we have the same engine, was to tie three lengths of 1/8" Dacron line (West Marine type that comes in 50 foot skeins), one each to a compression release and then led over the engine, out into the cabin, over the bridge deck and to the area of the wheel. By keeping track of which one was which, I was able to press all three releases open (read aft) and after pressing the starter button with no cylinder load, progressively close the releases by pulling the lines, center first and after hearing the engine cough into a semi-start, the other two one at a time. It's pretty Rube Goldberg but dog gone it works and that's all that counts.

So my suggestion to you is to always have a good length of that line aboard at all times......just in case.

Later,
Glyn

 

[Emerald]

Hi Sean,

Would you believe it if I said Glyn already got me back channel with the setup?

It's still good info to get out on the board for those not familiar with the technique - thanks.

 

[Glyn Judson]

Emergency starting on a string.

Sean, David and all, For those of you curious, I forgot to mention that David and I both have E31's powered with Yanmar 3GM30's. The compression release levers flip aft to open the exhaust valves, thus the neat little trick using the Dacron line to start the engine on an iffy battery. I'm sure the 2GM series of Yanmar would work the same way. Glyn