'83 115 water in gas and distribution block issues

[Danny C]

Was out on Sunday at full power and out of nowhere she (?83 Merc 1150 tower of Power) lost 75% of power and I could feel her surging like cylinders were firing at random. Able to limp back home but getting worse the whole time and barely running by the time I got to the ramp. Suspect water in the fuel because when I beach the boat I always get water over the transom and it gets up the fuel vent port. I usually cover it with tape but haven?t for the last few weeks, hence the suspicion of water in gas. Checked the gas last night and sure enough, separated and milky. Drained 5 gallons until all looked good. Pulled/cleaned all plugs and cranked engine with plugs out to try to purge any H2O. Have not pulled and flushed carbs because was hoping I could run fresh gas through and not have to get into a whole carb issue.

I will be dropping the boat in the water after work today to see if it fixed the issue.

Ran into something else during troubleshooting. Bought an inline spark tester and was getting spark on all but one cylinder. Later during checking two cylinders were not sparking. Multimeter says I was getting 0.1 ? 0.9 Volt signal to all coils that were sparking. Only getting 0.01-0.02 Volt signal to the ones not sparking. Tells me not the coil because coil isn?t getting enough signal to spark. 2 bad signals coming from same distribution block. Getting 0.1-0.9 V signal to the block at the corresponding low volt signal but only 0.01-0.02 signal out. Points me to a bad distribution block? Normally, at this point I would replace block but at $250-$300 I want to be absolutely sure first. I believe I had the same issue earlier this year (only on other block I think) and it ?magically went away? I was waiting for it to return. I believe before I noticed that if I reved the engine at neutral sometimes I could get the issue to correct itself. Sorry for the longwinded explanation but more info usually helps. Any thoughts?

Thanks,
Dan

 

[Chris1956]

Dan, When you say distribution block, you mean "switchbox"? The CDIElectronics has a troubleshooting procedure for the ign system of your motor. Your stator could be bad, your switchboxes could be bad or the wiring could be bad. Check the wiring for corrosion and loose insulation.

Try to isolate the issue to save some $$.....

 

[Danny C]

Thanks Chris, yes I mean switchbox, I keep calling it distribution box. I checked out the CDIElectronics site which is great for troubleshooting. Thanks. I will continue the troubleshooting.

Update, I took it on the water after work and idled fine then shot up on plane at WOT. Tried idle to WOT at least 10 times successfully. All smiles...then while some light cruising all of a sudden hesitation came back, started sputtering then fell to 25% power again. From there could not get it back to normal. All cylinders seem to be running low signal voltage at the coils but not going into the switchbox. I will continue to troubleshoot.

Question: anyone know how to take off the flywheel? I took the big nut off the top an thought that may be it but wouldn't budge. I am guessing it just needs more elbow grease to take it off as it probably hasn't moved in 15 years but maybe another bolt or two are holding it on.

 

[Chris1956]

The flywheel has a "W" shaped groove which matches the crankshaft and acts as a woodruff key. The stick a bit. Try some penetrating oil and a puller that bolts into the flywheel.

 

[Danny C]

After studying the CDI troubleshooting guide, I have a gameplan on testing the electrical system. One thing that I noticed is it calls for 150 Volts or more going from the switchbox to the coils. I am only getting readings in the 0.1-1Volt range on cylinders that I know are firing. This has me a bit confused. My first thought is I was reading the multimeter wrong and had it set 2 decimal places off but I do not think that is the case as the other readings are making sense. Has anyone taken voltage readings on the green wires at the from the switchbox to the coils? If so, were they in the 150V range?

 

[Chris1956]

OK, The Merc Service manual states that you need to use a Direct Voltage Adapter (DVA) to test voltage at the coil primary At 400 RPM, the primary side of the ignition coil will have 90-145 VDC. At 1000 RPM the voltage is 125-175VDC.

Since the coils are pulsed with voltage, it is likely your multimeter is too slow to read properly, hence the need for a DVA.

 

[Danny C]

Well that makes a lot more sense. I was going crazy with the voltages I was getting. Anyone know of a local place to pick up a direct voltage adapter?

By the way, checked Voltages during lunch (although with multimeter so I guess that doesn't mean much). All cylinders were firing like a champ. Would a low battery have any effect while engine is running? The issue seems to go away after the boats sits for awhile (in this case on a charger) but after some run time, its back...

 

[Danny C]

Just t off the phone with Merc Dealer and they told me they do not sell the DVA to the general public. I know I can get one online but to save time I was hoping to buy local. I think I am going to try to swap the switchboxes if for no other reason but to make sure wires are tight ect. Last time I had similar issues after swapping a few solenoids back and forth the issue magically went away for a few weeks. Hopefully this will happen again to get me through the holiday weekend.