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+ >> Your contributions help pay the fees associated with this list and help to >> keep it active. Please help by making a small contribution using PayPal at: >> https://www.paypal.com/paypalme/stumurray All contributions are greatly >> appreciated. > Your contributions help pay the fees associated with this list and help to > keep it active. Please help by making a small contribution using PayPal at: > https://www.paypal.com/paypalme/stumurray All contributions are greatly > appreciated.
Your contributions help pay the fees associated with this list and help to keep it active. Please help by making a small contribution using PayPal at: https://www.paypal.com/paypalme/stumurray All contributions are greatly appreciated.
