Percussive maintenance (Yanmar diesels)

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My helm position is a loooong way from the engines. One has two Yanmar-supplied extension sections added to the loom, the other one. Oddly enough it's the one with one extension that gives the most trouble

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Thought so. Th'rs yer problem m'dear!

The exact spec of relay is not critical but if you fit one slightly oversize it would not harm. ASAP sell one and have it in stock no 714852. It is 40 amp (plenty enough as it will only take the signal current to the solenoid not the starter motor current) and is a 4 terminal SRB601 type so simple to wire. About £15. You might get one cheaper from an autofactor or Maplins but this will do the jobbie OK.
A relay of this type will actuate with low voltage OK on the signal side as it is only closing light contacts on the supply. Fit as short a cable as you can from the battery to the power side. The starter motor main terminal would do fine. Any other info you need PM me any time.
 
I have had similar problems with Yanmar 3HM35F with and without these extension cables, solved the problem with a 12v/30a car relay(only £3-4) to operate the solenoid and placed close to the starter. No problems since.
 
Hi Snowleopard
GM starters are sensitive to volt drop during cranking. If the voltage drops to far it causes the solenoid to chatter eventually welding its self. How long is the extension loom from the panel to the engine? Yanmar quotes 6m or more requires start relay to be fitted. This would assist toward volt drop issue. Has the battery isolator been inspected and checked for any resistance in the circuit this is the first place i would check, they look good on the outside but corroded on the inside?
Its possible to start a 3GM by hand. Turn engine on handle as hard as possible the drop the nearest decompressor only one, the engine will try and start knock the rest of the decompressors the engine should fire. I would recommend buying a rope start kit from Marine Power tel: 02380 403918 speak to Pete.
 
I have cranked till my eyes almost pop out of their sockets but the instant I drop the valve on one cylinder it bounces back off the first compression.
 
The rope starter seems to work well, heard a lot of good reports. As this is attached to the crankshaft pulley not the cam shaft like the starting handle. All depends on how much space you have?
 
I can't believe you're still having starting problems..

May I ask, as none of the GM series engines I have used in 25 years have had the long term problems you have, are your starter batteries in the engine rooms or are you running long cables from external locations?

just a thought.
 
The engine start batteries are in the engine compartments. The wiring for the main starter cables is a total of one metre. All contacts cleaned and polished. The cabling to the start button and back to the solenoid coil on the other hand is very long, 8 metres on one engine, 15 on the other.

I think the advice above about voltage drop in that circuit is likely to be the answer.
 
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Never come across a rope starter. Any links?

[/ QUOTE ]shiver!

we had a rope start lombardini lump in one boat, single pot, frightening as hell to start. If the rope does not come off the pulley it drags the idiot back into the engine. I once saved my mates arm (possibly) by throwing myself onto him as his instinct was to try to pull against it.

The single pot would often start backwards too.

I have seen listers with recoil starts on them, though they were nice n simple to start in the handle anyways. I used to start a 3gm30 a few times a season by hand just to prove I could, I have not found it so easy on my current boat as the engine rooms are rather limited and it takes two of us to wind and decompress (with a broom over the winders shoulder to hold the lever). I intend to make a pulley system to try to make this a one woman (well, why not) job.

Have you considered using a power drill to start it up, you could get it going on one cylinder.
 
My long lead is approx 16ft, and thus far not given problems. Just to suggest that the low voltage side appears to work ok with extended leads.
 
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I have stripped a solenoid but found that the contacts are in a sealed compartment so unable to do anything about them.

SavageSD - The starters are pre-engaged so no bendix.

The problem appears to be dual - sometimes the solenoid can be heard to click as the button has pressed, indicating that the pinion has engaged but the contacts are not passing a current. On other occasions there is no sound at all so the solenoid isn't moving, as on this latest occasion.

Any ideas on what to use to lubricate the solenoid piston so it slides easier? I don't want to gum it up and make things worse.

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The pinion slides on a helix like a very coarse bendix on many starter motors. I have found 'gt85' quite good as a cleaner/lube, it allegedly leaves a trace of ptfe.
On a boat the pinion etc should not be getting covered in bits of clutch like on a car or bike.

I used to have a moto guzzi le mans, these have car type pre-engage starter motors, with solenoid in the 'catch rain position'. A 50p piece across the solenoid contacts was a common way to start the bike when the solenoid played up! The starter motor will actually work as a bendix type in this particular case. I think the pinion is on a helix to throw it out of gear when the motor starts and keep it in gear when the volts drop as the starter does its thing. With a guzzi, you can press the starter with the other hand so the solenoid does what it can.
Spending 50p bits with burns on two faces can be hard though!

Obviously take care not to short to earth. If there is a plastic barrier between the solenoid contacts, a cheapo spanner could bridge them.
 
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There is one heavy cable to the solenoid, the current goes through the contacts and into the motor and returns via the earth connection to the block. i.e. there is no external connection from solenoid to starter therefore nothing to short across. Also, if you bypass the solenoid the pinion won't engage so the starter would spin uselessly.

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Here is a piccy to help you understand
3gmstarter.jpg


Now I don't recommend shorting the studs as a normal way of starting the engine but if the thing won't start then it's a simple single person method that works. As lw395 has so eloquently explained, the gear does engage thanks to the helix.

Your apology is accepted /forums/images/graemlins/tongue.gif
 
Reading some of the other posts I recall that the solenoid itself draws a lot of current and can be very good at dstroying relays. If you short the solenoid terminal to the battery terminal (upper of two nuts in picture), bypassing the relay, the solenoid has the best chance of working. This will tell you if you need a new relay/better wiring.
I think a standard car relay may not be up to the job, because the solenoid is very inductive, tending to arc the contacts(?)
 
I think you are confusing yourself with terminology. The "Solenoid" is in fact a relay which is an electromechanical device which uses an inductive coil to close two contacts on a high amperage circuit. If you externally short the contacts the solenoid will be bypassed. This is a very bad and potentially dangerous thing to do and could cause, sparks, severe burns, and in the worst case probably weld whatever you have shorted it out with across the contacts causing a major melt down of your battery and/or wiring. It's certainly a fire risk and not a good idea at all. The problem here is that to close a couple of thumping great contacts efficiently you need to do it fast and with sufficient welly to prevent arcing. This requires power. Not a great deal, but more that can be delivered if the wiring in the primary circuit is down on voltage. What is proposed is a low power relay of a type that will actuate with low current draw introduced into the actuating circuit of the solenoid. Thus we have a "relay" operating a "relay." Answering another post, I think, because this is an important safety related issue I would not buy a cheap horn relay or such. No doubt it would do the job OK but I would worry about it's duty rating in this environment long term. The SRB601 relay I suggested is more than capable and at around £15 a time it's not expensive and will out last cheapies meant for intermittent use. One other issue is that it may well be that low power actuation of the solenoid over time will have damaged the contacts due to arcing and this fix alone may not be sufficient. It may be necessary to replace or at least clean up the solenoid contacts too and if this isn't possible then a new solenoid might be required also.
 
The 3GM starter is nominally 1kW so current is a nominal ~80amps - interesting sparks and, yes, possible welding if you're really clumsy. But the OP was in the position of having to clout the motor while his SWMBO operated the starter button, presumably 'cos "NOW" was when he wanted his engine to go. The short across the terminals requires no SWMBO, no ignition key, no starter button, just a suitable lump of metal.

If you add a relay it is probably a good idea to add a diode to reduce arcing due to back EMF.
 
No I'm not confused at all, perhaps didn't make myself very clear.
Some automotive relays are not very reliable when used to operate starter solenoids. This is an observation from experience, my own and others.
I believe this is because the solenoid draws quite a high current and is inductive.
Switch contacts often have much lower ratings for inductive loads compared with resistive.
A reverse diode, transorb or something similar could well help.
Hope that's clearer?
Cheers
 
Not really. With respect you are complicating the issue unnecessarily. An SRB601 with 40A capability does not need the protection of a diode. It does not matter if the load is inductive or resistive. It's the current that matters and that will be way lower than 40A to fully energise the coil of the solenoid. On either boats or cars its the KISS principle that is important. Buy good quality components, never have marginally specified kit and fit big fat wiring where you can and it will not only work but keep working. Simples!
 
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