Battery power is fine and spinning speed is not a problem, I have plenty of 
spin.

As you stated, I have suspected compression, but have not checked it yet.

I can check valves first to see if too tight and allowing leakage, but I would 
think that would be a problem with warm starts also.

And if valve seating is a problem, again that should also be a problem with 
warm starts.

Or could be worn rings that tighten up when warmer and lubrication has sealed 
the rings?

Either case, if low compression, either from valves or rings, this would 
dictate a rebuild or replacement.

 

The odd thing is that when you search online about this issue, there are a lot 
of people that have a similar hard starting issue with this particular engine.

 

Richard Arper

rtar...@wavecable.com

C&C 34+

 

From: Josh Muckley [mailto:muckl...@gmail.com] 
Sent: Friday, June 6, 2025 9:29 PM
To: Stus-List
Cc: Richard Arper
Subject: Re: Stus-List Re: Yanmar 3GM30F starting

 

I have a 3HM35F and it starts quick no matter the temperature outside.  I would 
suggest that it all comes back to compression. 

I think you have a year round problem that is simply manifesting during the 
cold. 
If the rings are a little sticky or the oil is thick then the cold makes it 
worse.  If the battery is undersized or week then the engine will spin slow 
during start and the cold will make it worse.  If the valve are already a 
little leaky and causing marginally sufficient compression then they will 
combine with the above and present as poor starting.  I have a compression 
tester and would strongly recommend starting there.  The only problem is that 
in order to test you need to remove the injectors.  Once you go to the trouble 
you might as well remove and clean the precombustion chambers and when you do 
that you'll need all new gaskets.  Who knows, you might even eliminate the 
cause before you even check compression. 

You really need a hot and cold compression but these engines require so much 
disassembly to get the compression in the first place the only numbers you ever 
get are cold.  I had someone run the starter while I was watching the gage.  As 
the engine spun the needle would "pump up". It took about 3 or 4 pumps before 
the pressure stabilized.  IIRC 425 to 450psi is the spec.  Internet AI is 
telling me 325psi is "good". 


Good luck, 

Josh Muckley 
S/V Sea Hawk 
1989 C&C 37+ 
Yanmar 3HM35F 
Solomons, MD 

Jun 6, 2025 22:40:04 Richard Arper via CnC-List <cnc-list@cnc-list.com>:

I've tried every imaginable throttle position, and nothing seems to make a 
difference. 
The manual says to use full throttle, and I've read that the full throttle 
position actually has an injection pump retard to it. 
Full throttle does seem to work better when cold, but after having started 
once, any throttle position seems to work fine, especially idle. 

Have not checked compression or valves yet, hoping that someone can tell me 
what the magic problem is. 
I don't have an adapter to fit the injectors for compression check. 
I can't imagine that valves are too tight, as they would become tighter with a 
warm engine and then even less compression, but could check. 
Still hoping that someone has cracked this egg before. 

Richard Arper 
rtar...@wavecable.com 

-----Original Message----- 
From: Dave S [mailto:syerd...@gmail.com] 
Sent: Friday, June 6, 2025 6:50 PM 
To: Stus-List 
Cc: Stus-List; Richard Arper 
Subject: Re: Stus-List Yanmar 3GM30F starting 

Do you give it a bit of throttle when you cold start?  (I know it’s not 
actually a throttle) 
Have you adjusted the valves?  Have you checked the compression? 
My 2gm20F was bulletproof but it preferred if I cracked the fuel open a bit 
when cold.  It also was noticeably …. Crisper… when the valves were adjusted 
correctly and after a good long high rpm run.  
Dave 
Sent from my iPhone 

On Jun 6, 2025, at 8:59 PM, Richard Arper via CnC-List <cnc-list@cnc-list.com> 
wrote: 

This issue may have been discussed previously before I joined the group, but I 
wanted to throw it out there. 
I have a 34+ with a Yanmar 3GM30F and its terrible to start when the 
temperature is maybe 50-60  degrees or less. 
That's a problem in Puget Sound where we sail all year. 
Once started, however, it starts perfectly all day after that with just a 
couple turns. 

I've read online about others having the same problem and offering starting 
procedures such as turning over with compression levers open to lubricate, then 
turn over with no fuel to heat up the chambers. 
There's even an air preheater that tractors use. 
But this doesn't solve the problem, and it's to the point where I'm ready to 
rebuild or repower. 

However, what's the root of the problem?  Is it poor compression? (engine only 
has 1600 hrs.) 
Is it bad injectors?  Other issues?  Trait of this particular engine? 

My 34 had a 2QM20 that started flawlessly under any conditions, so I know that 
it's not a lack of glow plugs. 

Richard Arper 
rtar...@wavecable.com 
C&C 34+ 
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