Yanmar YSM8 Won't Start

[SereiaBlue]

Hello all,

I have a Yanmar YSM8 that won't start. It hasn't ran since just before I took ownership earlier this year in May. The reason it sat was the failed exhaust coupler. I've since replaced the whole assembly (elbow, coupler, mixer and hose). With a 1000 amp battery jumper connected, it clicks once, nothing more. A couple of times I held the start button down and it sounded like it was turning, but very slowly.

What else do I need to consider so that I can get her cranked?

Side note: the alarm signal sounds when electrical power is turned on even without the key in the switch.

[a64pilot]

It has a decompression lever I believe?
If so decompress it and turn it over by hand to ensure the motor if free. Once you know its not locked up the next step is electrical connections, take them all loose one at a time and clean them with a wire brush and put a light coat of grease on them and reconnect them.
Once that is done if that doesn't fix it, jumper the solenoid directly, you know the screwdriver trick, if that doesn't work, I'd then pull the starter.
Often times the problem is with the ground wire and people forget to check the ground.

[SereiaBlue]

Great leads...following up now.

[SereiaBlue]

Tracking down a hand crank now. I did go the screw driver method at that moment...starter sounded like it spun a bit, but the engine did nothing at all. That was without the jumper connected so maybe amperage was an issue there.

[boatbod]

Measure the voltage from the starter positive lug to engine block both when the engine is just sitting and again when you try to crank it. If you have less than 10.5V when cranking you should look for a bad connection in the 12v supply cables. If the voltage is unchanged, you might need a new starter.

Sent from my SM-P900 using Cruisers Sailing Forum mobile app

[SereiaBlue]

Originally Posted by boatbod

Measure the voltage from the starter positive lug to engine block both when the engine is just sitting and again when you try to crank it. If you have less than 10.5V when cranking you should look for a bad connection in the 12v supply cables. If the voltage is unchanged, you might need a new starter.

Sent from my SM-P900 using Cruisers Sailing Forum mobile app

Thanks boatbod, that'll be at the top of the list next time out.
P.S. i sent the thanks not realizing it would not post here...still learning the forum.

[Badsanta]

Lots of info here for starting a yanmar. Please read cautions.

Sent from my SM-G920P using Cruisers Sailing Forum mobile app

[SereiaBlue]

Many thanks to all of those who offered ideas on solving this problem. It has been narrowed down to power supply. One of the batteries was actually bad. It was assumed it was good since it was recently on a charger with a 'good' indicator. That battery was replaced with a new Optima. With that, the engine spun briefly but mostly symptoms remained the same.
Further investigation led to the control panel. I'm positive this is the source of the issue. Will follow up again when results are in.

[SereiaBlue]

Originally Posted by SereiaBlue

Thanks boatbod, that'll be at the top of the list next time out.
P.S. i sent the thanks not realizing it would not post here...still learning the forum.

Starter was tested and it's in top shape. See update in recent post.
Thx!