1995 175hp Johnson - Ongoing electrical issues

[nphilbro]

I have the boat back home now and finally did some initial observation. Here are the issues I've dealt with much of the Summer/Fall.
1. Constant (solid) alarm condition
2. Intermittent failure to restart
3. No charging and no tach

I think (1) and (2) are related and might have narrowed the restart problem to a partially melted stbd side brown temp wire jacket. It appears the wire had pressed against the head at some point. It was an intermittent problem so hard to verify. The confusing part has been that the alarm would go on within a few minutes (or sooner) of starting the motor and remain on until d/c the alarm. The restart issue would never resolve itself until I removed the cowl - which would incidentally move the plug wires and temp wire. Does this motor have a fail safe to prevent restarting if it receives an overheat signal?

I'm well aware that a bad rectifier will kill the tach signal and charging but haven't done a diode test on it yet. My question is more specific to what impact having the wrong Spark Plugs and Plug Wires installed is to killing a R/R. I discovered that black copper conductor plug wires vs. the gray inductive wires and NGK BPZ8HS10 vs the recommended Champion QL78YC inductive plugs were installed prior to my ownership of the motor and didn't realize this until this week. Would that account for any of the 3 issues I'm dealing with? I'm not at all familiar with the operation of the Optical Sensor system but all the literature is quite explicit but haven't found any decent explanations. Of note: power pack and r/r units both appear to be replacements of original equipment (1997 Power Pack, 2007 rectifier).



The motor has been running great and estimate (by ear) that it's been getting up to at least 4k rpms, idles well...no noticable performance issues from that standpoint. I have two dedicated 700CCA starting batteries on a 1B2O Perko switch that I don't touch boat is back on the trailer. Batteries are well maintained with regular charging and usually start off reading between 12.7v and 12.8v at sunrise. Usually 12.3-12.4v when back home. I have two isolated SLA banks for the electronics and lights to prevent line induced RMI/RFI between the motor and each other.

 

[Bosunsmate]

Your ground in the middle photo looks too bent to be unaffected

 

[Bosunsmate]

Check your stator output, maybe the charging is only 12.4v from it.

 

[Bosunsmate]

Removing the cowl lowers the temp too, check for overheating with temp gun

 

[nphilbro]

I'll check that ground, hard to tell if it's really bent or just the photo. I've considered that it could have been a true overheat issue but I felt the heads the 2nd (and last) time it wouldn't restart and they were warm but certainly not hot.

Would a blown rectifier would cause a constant alarm? I should note, it isn't 100% solid on all the time...it will go on from the time we leave the dock then occassionaly stop for a few minutes before resuming as I increase speed to get up on plane. The VRO seems to be functioning correctly as it drains the tank at an appropriate rate. The alarm chirps when when key turned to the "on" position but DOES NOT come on until the motor is actually started.

Anyone have any input on whether the plugs and wires could be causing alarm or electrical faults with the charging system on this motor?

 

[Bosunsmate]

I dont think a blown rectifier would cause an alarm. unplug the alarm wiring to the vro and see if that silences it

 

[nphilbro]

I'll track the source of the alarm down. I have another buzzer I can dig up to compare the resistances then backtrack from there. Again, my biggest concern is what damage could have been done not using inductive plugs and wires. The R/R is about $250 and the one on here only had about 25 hours put on by the previous owner. He could have blown it himself disconnecting the battery but I'd like to get a better idea before I drop the $$ without fixing the real cause of the problem.

 

[nphilbro]

Update:
I pulled the rectifier off this afternoon after running the bench tests and with inconsistent readings. The two forward bolts were much harder to remove than than the two rear bolts. A lot of corrosion in the threads which indicated, to me, an open ground. I repeated the tests with the rectifier off the motor and when testing to ground noticed the entire body and bolt holes were painted with thick epoxy or something and the engine facing side of the unit is isolated from the block by a gasket. The one ground wire attached to the bolt on top (kill switch) worked but the unit itself wasn't grounded to the block at all. There was a lock washer that should have have made the connection but it didn't penetrate the paint.

I took a stainless steel brush and cleaned up the bolts and scraped enough paint off two opposing bolt holes to complete a good connection with a lock washer. I also ran one additional ground wire to the another part of the block at an adjacent forward bolt. Additionally, I cleaned all the other ground wire connections where they connect to the block.

I fired it up and my tach worked right away. I couldn't tell if it was charging the starter battery because I unplugged the charger only about 15 minutes prior so resting voltage still read 12.9V on my Multimeter. The voltage while running at idle dropped to 12.7 and held steady well past the warm-up RPMs dropped then put it in gear (reluctantly) and gave it about 1800rpm but didn't notice any change in battery voltage. As soon as I shut the motor off the battery voltage bounded right back to 12.9V. Not sure if this is normal or if I still have bugs to work out.

I guess I'll know if they are charging next weekend.

 

[bob johnson]

I have a 115 with optical sensor, and I have had the weirdest alarm since I got the motor....the alarm goes off exactly 2 minutes after I turn the key on and it goes off after 10 seconds... the light for HOT comes on during that time...but the motor isn't hot...( checked with infared, plus its happens even when the motor hasn't been started!! )

I just live with it.. I installed a temp guage in each head to monitor the temps..and I installed a water pressure guage....

the alarm will also go off while running later on, and shuts itself off....and the temperatures are fine.....

 

[nphilbro]

I've got two alarms from other control boxes I'm going to try. I get similar strange alarms at times and that's why I was wondering if they were related to the plugs and wires that are on there.
I moved my key ignition to the helm dashboard so I'm also going to check what the purple wire is connected to and verify everything is connected correctly. I think the helm side purple wire coming off the key switch is only powering the gauges and alarm.

I have two 12GA Red power cables coming direct to the helm off the battery switch to connect accessories I don't want controlled by the ignition.

I think they are all isolated but it's a cramped space and I have to work upside down so it's possible I have one constant power source bridging the 'on' circuit somewhere. I suppose that could wreak all kinds of havoc depending on what's bridged.

I share a common ground bus under the helm and in the battery compartment for switchable batteries. I have another switchable system I know is completely isolated for the downriggers, VHF, GPS, and fishfinder.

 

[nphilbro]

..I installed a temp guage in each head to monitor the temps..and I installed a water pressure guage.....

Bob, what components did you go with for the temp sender gauge? I've considered this for a long time but could never get a clear answer to the question. It seems like "sensor" and "sendor" units were always interchanged or confused. I'd just like to put a gauge on the dash for each head telling me temp at the top of each head. I've I'm running 30-50 miles offshore it would be nice to have the option for indication that something's going awry..and to what extent..before having to go into full safe or shutdown mode.