I have a 1977 O'day 27 that has a YSB 12 Yanmar diesel engine. The engine is becoming more and more unreliable. I won't start when it is hot. It has never quit on me while running it. It always starts when cold. I have had several mechanics look at it. Fuel lines, fuel pump, filters and injectors have inspected, batteries replaced, exhaust elbow replaced....It took me a while to figure out that it was a hot engine that would not start. I found that if the decompression lever was pushed, I could jump start the engine. I rigged a string to the lever so that I could release the lever from the cockpit while I turned the key. Last time out, the engine smelled hot. I tried to start the engine after 10 minutes the engine would not start. I would consider re powering but I am not sure it is worth it. Does the boat have any value as it is. After all it is a "sail" boat.
Ysb trouble shooting
- Thread starter dougphurd
- Start date
99% of the time when an engine won't start because it's hot, the answer is the WIRING.
Check all the wires & connections, especially the ground at the back of the engine.
You are only the 1,000,001th to ask this question.
Good luck.
Check all the wires & connections, especially the ground at the back of the engine.
You are only the 1,000,001th to ask this question.
Good luck.
We need more information to help. When trouble shooting anything, always ask the basic 4-W questions. “What works? What doesn’t work? When did it stop working? Was there any other work done around the time it stopped working”.
Looks like you worked on a lot of stuff (by the way you only have one injector) and still have a problem.
- Did the starting problem get worse over time or suddenly?
- Does the starter motor to turn over the engine as fast as it did in the past?
- Will the Yanmar start reliably if you use the decompression lever to remove the compression load and let the starter get the motor up to speed for a couple of seconds and then release the lever or if you heat the incoming air for a couple of minutes?
- What is the measured starter terminal voltage (referenced to the starter case) before engaging the starter and while it is running? The voltage should be about 13volts before and greater than 9volts when the starter is running.
My 1979 CAL has a Yanmar YSM12 (basically the same motor) and last year she became sluggish to start. Slow turning over, not enough power to turn over if stopped on the compression cycle, blowing the 200amp battery fuse (normal starter load should be about 75amps), etc. But she would always start if I used the decompression lever to remove the load for a couple of seconds until the starter got the Yanmar up to speed or if I heated the intake air for a couple of minutes with a hair dryer if at a dock or a butane torch if at sea. Investigation found that there was nothing wrong with the electrical or the fuel systems but the starter was not able to deliver enough power get the Yanmar up to speed to generate enough compression heat to ignite the fuel (read your Yanmar manual). I order and installed an “el cheapo” new starter from an ebay store made for all small Yanmar single and twin cylinder diesels. It had lots of power to overcome the compression stroke but the speed was about 120RPM. Probably OK for a two cylinder motor but a single cylinder needs double that starter speed. I then took my original starter to a local automotive and marine electrical shop and had them totally rebuild it installing new bearings, brushes, high current contacts, etc. She now starts like new, always on the second compression cycle. The YSM-12 is good a new, just like the battery rabbit she keeps on going and going and going…….. I should have done that to begin with.
What I’m trying to say is sometimes problems aren’t what they appear to be.
Please check the above questions and let us know what you find.
Looks like you worked on a lot of stuff (by the way you only have one injector) and still have a problem.
- Did the starting problem get worse over time or suddenly?
- Does the starter motor to turn over the engine as fast as it did in the past?
- Will the Yanmar start reliably if you use the decompression lever to remove the compression load and let the starter get the motor up to speed for a couple of seconds and then release the lever or if you heat the incoming air for a couple of minutes?
- What is the measured starter terminal voltage (referenced to the starter case) before engaging the starter and while it is running? The voltage should be about 13volts before and greater than 9volts when the starter is running.
My 1979 CAL has a Yanmar YSM12 (basically the same motor) and last year she became sluggish to start. Slow turning over, not enough power to turn over if stopped on the compression cycle, blowing the 200amp battery fuse (normal starter load should be about 75amps), etc. But she would always start if I used the decompression lever to remove the load for a couple of seconds until the starter got the Yanmar up to speed or if I heated the intake air for a couple of minutes with a hair dryer if at a dock or a butane torch if at sea. Investigation found that there was nothing wrong with the electrical or the fuel systems but the starter was not able to deliver enough power get the Yanmar up to speed to generate enough compression heat to ignite the fuel (read your Yanmar manual). I order and installed an “el cheapo” new starter from an ebay store made for all small Yanmar single and twin cylinder diesels. It had lots of power to overcome the compression stroke but the speed was about 120RPM. Probably OK for a two cylinder motor but a single cylinder needs double that starter speed. I then took my original starter to a local automotive and marine electrical shop and had them totally rebuild it installing new bearings, brushes, high current contacts, etc. She now starts like new, always on the second compression cycle. The YSM-12 is good a new, just like the battery rabbit she keeps on going and going and going…….. I should have done that to begin with.
What I’m trying to say is sometimes problems aren’t what they appear to be.
Please check the above questions and let us know what you find.
If turning over at normal speed on starter. The first thing I would check is valve to rocker setting. Next would be compression,worn rings is often the problem with Diesel engines not starting when hot.
Sb12 is a great engine to me well worth the time and trouble to repair.
Sb12 is a great engine to me well worth the time and trouble to repair.
I worked on a Yanmar last year with starting issues....and replaced the battery/crank cables. Problem solved..
a lot of sailboat with diesels under the sole and wiring up to a start switch in the cockpit suffer from a deterioration of the wires and connections in that long wiring run . the voltage drop from deteriorated connections makes it very difficult to start the engine . replacing this wiring is the 1st thing to try. putting a momentary start switch between battery and starter and bypass the key switch in the cockpit is another option and allows you to start the engine from the cabin not the cockpit.