Yanmar 3GM30 27HP starting issues

[MickiUsh]

Hi all,

I'm having problems to start the engine in some situations.

Sometimes I start the engine without problem and after leaving the port and stopping the engine and after a couple of hours want to start it again, it does not even move, just as if it has no battery. No noise at all. To start the engine I have to decompress and then it starts. The thing is that it does this not allways but sometimes and now more frequently.

Any idea where to check or what?

Regards,
Micki

[MickiUsh]

Four different mechanics checked the engine, starter, etc. Nobody found the problem.

[Wotname]

Welcome aboard CF, MickiUsh.

It sounds to me like you have an intermittent electrical problem with the starter motor circuit.

Most likely some corrosion at a terminal post or a loose connection. Try removing all the leads and cleaning the connections - especially the negative lead from the engine back to the battery.

If you are electrically competent, measure the volts at the starter motor and the battery terminals when the fault is present - this should point you towards the problem

[Wotname]

There is also a fairly common problem with the 3GM30 (& 2GM20) start circuit in so far the wire from the start switch to the starter motor solenoid is somewhat undersized and once you get some corrosion in the interconnect plugs, the solenoid fails to fully engage.

There are many threads about it and the usual fix is to add start relay near the starter motor to power the starter motor solenoid.

[sck5]

I solved exactly this problem on my old boat by getting a new wire to replace the undersized one along with cleaning up all the connections. It worked, at least for the three years I still owned the boat.

[model 10]

[QUOTE=Wotname;
If you are electrically competent, measure the volts at the starter motor and the battery terminals when the fault is present - this should point you towards the problem[/QUOTE]

You should explain to the fans why a series starter motor terminal will only show 9v during a start.

[Wotname]

Originally Posted by Ecos

You should explain to the fans why a series starter motor terminal will only show 9v during a start.

I not sure how this is helpful to the OP's problem nor do I know why you make this claim however I can only assume you have mistakenly attributed such a claim to me.

For the OP, volts at the starter motor terminals should be relatively close to the volts at the battery terminals while cranking. Alarm bells should sound if the difference gets higher than say 2V. However the current available from the start battery is just as important and I would expect you to have at least 10V at the starter motor terminals while cranking - a 3GM30 doesn't have a really high start current requirement.

[NYSail]

Yanmar wire harness is under sized. You have to either replace the wire that goes from the panel to the starter or add a basic solenoid close by. On my last boat the 3hm35f had same issue that I fixed with the additional solenoid. Mean time you don’t need to decompress just jump the starter with a screw driver.
Btw as was mentioned do also clean all your terminals.....
Good luck!

Greg

Greg

[Compass790]

Well I shoudn't comment on this as I'm an electrical newbie but I would say that I can't fault Wotname with any electrical advice from him i have received.
In my uneducated opinion he knows his stuff about electricity. He is some kinda avionics helicopter tech bloke ( guy in USA english) Guess what happens in a helicopter if the electrics fail?
My guess, about chopper maintenance people ( not entirely uneducated ) is the scrutiny on chopper technicians is probably close to surgeons without the remuneration.
But again you make your own judgement.

[model 10]

[QUOTE=Wotname;2962943]I not sure how this is helpful to the OP's problem nor do I know why you make this claim however I can only assume you have mistakenly attributed such a claim to me.


I'm sorry. I thought you could explain/show, why there is such a big voltage drop during cranking. Just saying there is a 2-3 volt does not mean anything to some of us. I've checked good working starter systems and the v at the starter is below 10 during cranking.
With a giant house bank it will be different.

[donradcliffe]

I suspect the OP's problem is that the starter solenoid is not being pulled in, and measurement of voltage from the big starter terminal will show near battery voltage. No noise, no voltage drop. The voltage to check is from the small wire to ground at the starter.

The OP didn't say what kind of boat he has, but some Catalinas were miswired so that the starter circuit was fed by the preheat button. This meant that you had to hold the glowplug button down AND hit the starter. The problem with this arrangement was that with weaker batteries/wiring there just wasn't enough voltage on the starter wire to engage the starter solenoid.

[zengirl]

I posted this before and don't know if it will apply to you. I had the same problem and couldn't figure it out. Turns out that when I pressed the starter button in the middle it doesn't work. Fiddled around and now it starts every time. I have to put the pressure on the left side of the button rather than the middle. Seems stupid, but it works for me.
My engine is a 3ym30 so may not apply, but worth a try.

[bjp447]

Originally Posted by MickiUsh

Hi all,

I'm having problems to start the engine in some situations.

Sometimes I start the engine without problem and after leaving the port and stopping the engine and after a couple of hours want to start it again, it does not even move, just as if it has no battery. No noise at all. To start the engine I have to decompress and then it starts. The thing is that it does this not allways but sometimes and now more frequently.

Any idea where to check or what?

Regards,
Micki

Had the same type issue on my 3m in my Ranger Tug. Troubleshot for 2 years. Heavier wires, new starter, new ignitions switch, cleaned terminals until they shined. Finally turned off horn, relays working , changed them anyway. Starter relay fixed problem. it
appears that the starter relay was not getting enough amps to the solenoid even thought the solenoid showed volts when the switch was turned on

[MickiUsh]

Thank you all, will try all what you propose to do. And will come back with the news. Thanks again.

[svJasmine]

I have had this problem with this same engine. The harness is a bit undersized and is prone to corrosion. There is an inline fuse in the harness that can be problematic, but the best thing is to just rewire the starting circuit with heavier marine wire.

Or, jumper the start switch on the starter soleniod with a good wire to verify it isn't the actual starter that is the problem.

There are only a few circuits in the harness.

Hot and ground to the panel
sender for oil pressure
sender for temp sensor
tach sensor wires
neutral safety wires (I think, but I don't use them)
lights for the panel
and the alarm circuit
there is also some wiring to check the lights on the panel and stuff and turn the tach light on.

the service manual has a schematic and I have seen it online to download.

Rich