First start in awhile…

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Inter20sailor

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Sep 18, 2009
58
Beneteau Oceanis 38 Long Beach
Greetings,

When I had a Yanmar 3GM30, I was able to pull the decompression lever to build oil pressure before the start. This was done when significant time passed since the last start. Now that I have a newer boat, with the 3YM30, there is no decompression lever. Is there a procedure that would allow engine turning to build pressure and delay the start?
 
Davidasailor26

Davidasailor26

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May 17, 2004
5,098
Beneteau Oceanis 37 Havre de Grace
You might be able to press the engine stop button, which is a fuel cutoff. I’ve never tried this with my 3YM30 and would be more worried about flooding the cylinders with water than trying to build oil pressure.
 
dmax

dmax

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Jul 29, 2018
991
O'Day 35 Buzzards Bay
Hayden Watson said:
If your boat has a manual kill cable you can leave it pulled out and it will crank forever and not start. Don't ask me how I know this. :facepalm:
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When I got my first diesel, I thought the cut-off switch was a choke - I developed a procedure to start it up: crank for about 3 seconds with the "choke" all the way out and then push the choke in, always started right up when I did this :) And, I pulled the choke all the way out to shut the engine down :) About half-way through the season I stumbled upon the real purpose of the choke.
 
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J

jeepbluetj

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Jan 18, 2016
782
Catalina 387 Dana Point
Calif. Ted said:
Worse perhaps if you do it at the fuel dock with witnesses, not that I would know anything about such an event. :doh:
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Particularly bad when the Admiral says rather loudly "Maybe it's not starting because you left the choke on" and starts to giggle.

Only ever made that mistake once. Backing out with shore power connected? I can do that once every two months or so.
 
B

Benny17441

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May 24, 2004
7,131
CC 30 South Florida
Engine oil thickens when cold. Cold engine oil can place a drag on the starter motor causing it to turn the engine at a slower pace. Cold engine oil because of it's thickness will result in higher oil pressure until the engine reaches operating temperature. I don't think oil pressure build up is a concern, it will build up on its own as the engine turns and starts. Just getting the starter to turn the engine a little faster by opening the throttle to around 2/3 will do the trick, but be ready to throttle down when the engine fires. The purpose of the decompression lever was to allow to turn the engine by hand but with larger engines it became impractical and have been eliminated.
 
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jviss

jviss

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Feb 5, 2004
6,748
Tartan 3800 20 Westport, MA
Benny17441 said:
Just getting the starter to turn the engine a little faster by opening the throttle to around 2/3 will do the trick, but be ready to throttle down when the engine fires.
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@Benny17441 what do you mean by this? Although the speed control on boat diesels is usually called the throttle (much to my chagrin), there is literally no throttle on a diesel. The control is a speed control, which is adjusting a governor, and the high pressure pump increases or decreases fuel supplied to keep the engine at the speed selected.

I don't understand how moving this control has any influence on how fast the engine spins under starter power before it starts.
 
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Hayden Watson

Hayden Watson

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Apr 5, 2009
2,825
Catalina '88 C30 tr/bs Oak Harbor, WA
jviss said:
@Benny17441 what do you mean by this? Although the speed control on boat diesels is usually called the throttle (much to my chagrin), there is literally no throttle on a diesel. The control is a speed control, which is adjusting a governor, and the high pressure pump increases or decreases fuel supplied to keep the engine at the speed selected.

I don't understand how moving this control has any influence on how fast the engine spins under starter power before it starts.
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Very true. When the engine is off, the governor is not turning so it sets to injector pump to max fuel output. As the RPM's increase to the set-point, the governor reduces the fuel flow to limit the RPM's to the set point. The only thing that advancing the speed lever will do it make the engine run faster after it starts. Before it fires, it will have no effect.

I really get a kick out of watching people "pump the throttle" a few times before they hit the starter. There is no accelerator pump in a diesel like is in a gas carburetor so that has zero effect.
 
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jviss

jviss

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Feb 5, 2004
6,748
Tartan 3800 20 Westport, MA
Hayden Watson said:
I really get a kick out of watching people "pump the throttle" a few times before they hit the starter.
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If you saw me it might appear I'm pumping the "throttle," but I'm actually moving the speed control through to range to find my preferred starting speed point, which I can usually hit dead on, at 1,000 RPM.
 
Hayden Watson

Hayden Watson

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Apr 5, 2009
2,825
Catalina '88 C30 tr/bs Oak Harbor, WA
jviss said:
If you saw me it might appear I'm pumping the "throttle," but I'm actually moving the speed control through to range to find my preferred starting speed point, which I can usually hit dead on, at 1,000 RPM.
Click to expand
I was not talking about advancing the speed control to a higher set point. I was refering to those I have seen pump the "throttle" 4 or more times. Those folk also end up leaving the speed in the highest settling so that when it starts it revs to the limit of the WOT governor which is the worst thing that can be done to a diesel on startup. The only time that I have advanced mine was when after replacing the motor mounts my idle RPM's were lower than before and it would be very rough at idle. After I adjusted it I was able to go back to starting at idle and letting the oil pressure come up before advancing it to about 1000 rpms until I got the lines untied. No matter how cold it is, I only warm up for as long as it takes me to untie. I then need to motor at idle speeds for another 3-4 minutes to clear the break water. By then, the coolant temp is ussually up to about 100º. Once it is at 100º I go to 1400rpm until I reach 160º when I go to my cruise setting.
Idling and no-load running is hard on them and I keep it to a minimum.
In the same regard, I shut down the engine as soon as the boat is secure. It has ran at idle long enough to cool down from the break water to the slip.
 
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