Outboard Compression

[Dave R]

Originally Posted by Denny Crane

I think I'm at my limit mechanically so if anything else comes up it might be the end!

Not even close. The next thing that comes up just means you get to learn something else and maybe get to (justifiably) buy more tools. It gets easier and easier the more you do it.

One of my favorite recent troubleshooting events happened like this:

My wife and I were visiting our slip neighbors on their boat after dinner one evening this past Summer. The boat captain is very handy and the conversation eventually turned to boat troubles. He confessed that he was confounded by a problem with his generator. 3 minutes later, we're in the engine room troubleshooting, of course. Mind you, it was probably 9 PM by then, but we are both kind of OCD about this kind of stuff...

Anyway, the genset would not crank and the battery and starter worked fine. He had found and replaced a faulty "ground" cable (problem 1) on the engine earlier that day with no improvement. I took a quick look and noticed that there was an arc suppression diode on the starter solenoid. I got my DMM and tested it, and found it was shorted (problem 2). Removing the diode did not help (it can work without the diode, it's just there for solenoid longevity) so I suggested the main controller board had been damaged by the shorted diode and a few minutes later, proved it (problem 3). The main board had acted like a fuse and one of the copper conductors (lands) on the board had been vaporized. I went back to my boat and got my butane soldering iron, a spool of solder, and a piece of bare copper. A few minutes later, the board was fixed and the engine was finally cranking over like it should. Unfortunately, it would not start. On to problem 4...

We determined that the engine was not getting fuel, so the first check was the fuel filter which was clogged (problem 4), we cleaned it out only to discover the engine was still not getting fuel. Next step was to look at the fuel pump. We opened it up and found that water in the gas had caused it to rust a bit and lock up (problem 5). We freed it up and got it working again pretty easily, put it back in place and still got no fuel flow. We traced the fuel line back to the tank and found a check valve at the top of the tank. We took it off and found it had rusted closed (problem 6). Like the fuel pump, it took little effort to get it working again and we got it re-installed. Now the engien was getting fuel, but it still would not start...

The next obvious check was the carburetor. We took it off, took it apart and found lots of crud. There was one particular chunk of crud blocking the pilot jet completely (problem 7) and when we removed it, put the carb back on the engine, and cranked it, it fired right up and the genset has worked great ever since.

We put a new diode on the solenoid the next day and added a fuse so that it cannot cause the same problem again. We also got rid of the water in the fuel tank.

That's my idea of an interesting evening. FWIW, I had only recently learned about arc suppression diodes this year, on the internet, and if not for that, I think we would have never got past problem 2, that night. I also just happened to have a bag of 100 spare diodes on hand (that I got on ebay for a couple of bucks) because my 27 year old boat has them installed on every one of the dozens of switches and relays.

[8gv]

Originally Posted by Dave R

Not even close. The next thing that comes up just means you get to learn something else and maybe get to (justifiably) buy more tools. It gets easier and easier the more you do it.

One of my favorite recent troubleshooting events happened like this:

My wife and I were visiting our slip neighbors on their boat after dinner one evening this past Summer. The boat captain is very handy and the conversation eventually turned to boat troubles. He confessed that he was confounded by a problem with his generator. 3 minutes later, we're in the engine room troubleshooting, of course. Mind you, it was probably 9 PM by then, but we are both kind of OCD about this kind of stuff...

Anyway, the genset would not crank and the battery and starter worked fine. He had found and replaced a faulty "ground" cable (problem 1) on the engine earlier that day with no improvement. I took a quick look and noticed that there was an arc suppression diode on the starter solenoid. I got my DMM and tested it, and found it was shorted (problem 2). Removing the diode did not help (it can work without the diode, it's just there for solenoid longevity) so I suggested the main controller board had been damaged by the shorted diode and a few minutes later, proved it (problem 3). The main board had acted like a fuse and one of the copper conductors (lands) on the board had been vaporized. I went back to my boat and got my butane soldering iron, a spool of solder, and a piece of bare copper. A few minutes later, the board was fixed and the engine was finally cranking over like it should. Unfortunately, it would not start. On to problem 4...

We determined that the engine was not getting fuel, so the first check was the fuel filter which was clogged (problem 4), we cleaned it out only to discover the engine was still not getting fuel. Next step was to look at the fuel pump. We opened it up and found that water in the gas had caused it to rust a bit and lock up (problem 5). We freed it up and got it working again pretty easily, put it back in place and still got no fuel flow. We traced the fuel line back to the tank and found a check valve at the top of the tank. We took it off and found it had rusted closed (problem 6). Like the fuel pump, it took little effort to get it working again and we got it re-installed. Now the engien was getting fuel, but it still would not start...

The next obvious check was the carburetor. We took it off, took it apart and found lots of crud. There was one particular chunk of crud blocking the pilot jet completely (problem 7) and when we removed it, put the carb back on the engine, and cranked it, it fired right up and the genset has worked great ever since.

We put a new diode on the solenoid the next day and added a fuse so that it cannot cause the same problem again. We also got rid of the water in the fuel tank.

That's my idea of an interesting evening. FWIW, I had only recently learned about arc suppression diodes this year, on the internet, and if not for that, I think we would have never got past problem 2, that night. I also just happened to have a bag of 100 spare diodes on hand (that I got on ebay for a couple of bucks) because my 27 year old boat has them installed on every one of the dozens of switches and relays.

What a great adventure!

[Denny Crane]

You are a true Doctor of your craft! You had me lost at "the genset would not crank!" Thanks again.

[Formula260SS]

Since this thread speaks to older outboards here's one - My 1987 60HP Johnson which runs great melted it's Rectifier and somehow the engine still ran and has been this way for who knows how long. (only use the boat on occasion)

I do have a service manual and the stator and new rectifier check out OK using a Fluke. However the output from the rectifier is up around 16 Volts which is really too high. Question is - do all the old outboards with Rectifiers run high on voltage? I did order a Regulator / Rectifier which I believe will cure the high voltage but thought it a good question to throw out there. I don't have any electronics on the boat besides Nav Lights but worry about the Power Pack and other engine components burning out. It has eaten a few choke solenoids which I'm now thinking could be a victim of the high voltage.

Thoughts ? - Thanks

[Dave R]

Originally Posted by Formula260SS

Since this thread speaks to older outboards here's one - My 1987 60HP Johnson which runs great melted it's Rectifier and somehow the engine still ran and has been this way for who knows how long. (only use the boat on occasion)

I do have a service manual and the stator and new rectifier check out OK using a Fluke. However the output from the rectifier is up around 16 Volts which is really too high. Question is - do all the old outboards with Rectifiers run high on voltage? I did order a Regulator / Rectifier which I believe will cure the high voltage but thought it a good question to throw out there. I don't have any electronics on the boat besides Nav Lights but worry about the Power Pack and other engine components burning out. It has eaten a few choke solenoids which I'm now thinking could be a victim of the high voltage.

Thoughts ? - Thanks

As far as I know, the charging system on that engine is unregulated, so 16 volts is probably normal if the battery is charged up fully. It will be a lot lower if the battery is discharged. If you are concerned about too much voltage, CDI makes a regulated rectifier that should bring it down to 14 volts or so. It's part number #193-3408 and they cost about 70 bucks.

[Formula260SS]

Originally Posted by Dave R

As far as I know, the charging system on that engine is unregulated, so 16 volts is probably normal if the battery is charged up fully. It will be a lot lower if the battery is discharged. If you are concerned about too much voltage, CDI makes a regulated rectifier that should bring it down to 14 volts or so. It's part number #193-3408 and they cost about 70 bucks.

Thanks Dave that's what i thought and ordered.

[Denny Crane]

It would have been too easy if my outboard story ended there. The engine was running beautifully in my driveway and I was planning to winterize it when it stopped out of the blue and I couldn't turn it over again. When I went to prime it again I noticed the prime bulb was compressed and I couldn't return it back to normal. Any ideas?

[Denny Crane]

I know where the vent is but I don't know how to check that.

[Dave R]

It's either a clogged vent on the fuel tank or a clog blocking fuel from flowing from the pickup in the tank to the bulb. The clog cannot up downstream of the bulb.

Assuming it's not a clogged vent, one common cause of this is a blockage in the fuel line caused by de-lamination of the inner layer of fuel line itself. If the fuel line is more than 10 years old, consider replacing it.

It may also be caused by crud clogging the fuel pickup in the tank. Pull it out and have a look.

There may be a check (anti-siphon) valve where the fuel line comes out of the tank. Check that, might be stuck shut.

[Denny Crane]

Great ideas once again. I changed all the fuel lines from the gas tank out a year or two ago. Come to think about it when I went to siphon the old gas out with a small 12v pump I had trouble pulling gas at first. I may try an external gas tank first and go from there. Thanks!

[Dave R]

Originally Posted by Denny Crane

Great ideas once again. I changed all the fuel lines from the gas tank out a year or two ago. Come to think about it when I went to siphon the old gas out with a small 12v pump I had trouble pulling gas at first. I may try an external gas tank first and go from there. Thanks!

If there was any sign of water in the old gas, I bet the check valve ball is rusted and sticking in place.