Optimax 150 starting problem

I have twin 2006 Optimax 150s with about 420 hours on each. This past week my port #2 air injector failed and was replaced - the first replacement of a failed part outside of the onboard oil tank a couple of years ago. I ran the boat about 4 hours the day after replacement - no issues. The next day, we ran about 25 miles downlake (South Fork Holston - VA/TN) to Cliff Island to jump. After being off for maybe 30 minutes, my port motor just clicks - the starter gear would engage the flywheel but not turn.


Serial numbers are 1B275781 and 1B275020 - I'm not positive which is which.


My electrical setup has port, starboard, and house batteries - let's call them A-B-C. So, as originally, was
port-A, starboard-B, house-C. I have a BEP cluster with VSRs so either motor can charge the house after the start battery is charged and I can parallel the two starting batteries. I have 00 gauge wires running to the motor after going through a big fuse (I forget if 200A or 300A) in the console where the batteries are.


My first thought was a weak battery.


1. All batteries showed 12.6+V (can't recall hundredths value) with no load per multimeter.
- all are AGM and 6 months to 2 years old and ample rated capacity
2. With starboard shutoff, when I paralleled A&B, the port motor cranked.
3. I also found one blown fuse on the port motor - the 5A fuse on the motor. I replaced that fuse.


Thinking that maybe that fuse controlled the charging circuit (incorrectly I believe now) and that Battery B was discharged despite showing 12.6+V , I switched Battery C to port motor and Battery B to house. Port motor started again on C (2-3 minutes after having started with A&B paralleled) and we ran back to our dock. All 3 batteries showed 13+volts, so all 3 were charging. Problem solved? Not yet.


After sitting another 30 minutes, when I tried to start port again, same behavior as earlier. Wanting to get in some watersports on our last day at the lake after missing time due to the air injector, I simply paralleled B&C with starboard motor off, started port, cut the parallelling, started starboard and ran for 2 hours wakeboarding, kneeboarding, and tubing. After we finished, I let it sit 5-10 minutes and port started fine on C only. I then put it on the trailer.


I noticed one other odd thing on the port motor. In our last couple of hours on the lake, I had my SC1000 tachs set to show voltage on each motor.


Idle - over 15 seconds, port motor fluctated wildly on voltage
- 14.8, 15.3, 13.7, 13.5, 14.7 for example based on video I shot - so, from 13.5 low to 15.3 high
In contrast, starboard motor at idle was steady and ranged from 14.0-14.2 over same 15 second time period


At speed, port motor had much less fluctuation over 15 seconds
- 14.2-14.4V range at 3400 rpm




I'm looking for suggestions on what to check. Currently on my list are:


1. Confirm if 5A fuse blew again and see what it does
2. Check all connections from battery to starter motor
- I've run probably 50 hours since I last had anything disconnected


To me, it seems like after the motor sits for a while, the starter requires excessive amps to turn, and that is why paralleled batteries gets it started. But, at the same time, the substantial voltage fluctuation at idle makes it seem like something else is going on also.


The motor is very clean - although it is about 50% saltwater usage, the mechanic (at Laurel Marina, a Mercury Premier certified mechanic on the lake) thought it was a freshwater only motor as it is so clean with no corrosion anywhere.


I appreciate any suggestions on where to go with troubleshooting. I'm going to get back on it next Saturday morning but hope to have a game plan on what to look for.


Thanks for any input.

Update - I ordered a DC cable clamp for my multimeter and am going to measure amp flow in the starting circuits this weekend to compare the port and starboard motors.

I am having a hard time seeing something on the battery end as the cause with the behavior shown. I suspect something is wrong on the motor end. In addition to a loose wire, other ideas I had about items that could cause this behavior include
- starter solenoid (I actually have a spare one of those)
- starter motor (seems unlikely based on reading about these motors)
- something causing intermittent increased load on the drive belt
------ compressor?
------ other items served by the drive belt

After this weekend I expect to have some amp flow comparisons between the two motors that hopefully will nail down why extra supply battery is needed at times.

OK- let's start at the basics, that's one mixed up mess of devices and connections!

Rules of the Road:

-Each engine has ONE DEDICATED STARTING BATTERY.

-No inter-tying devices... they cause just the type of problems you are experiencing.

-There MUST be a common ground cable connection between ALL batteries. Same type/gauge as your battery cables.

-NEVER disconnect or change battery switches, cables, connections, etc. while an engine is RUNNING.

When you've got it all back like this, let's see where you are at, and start from SCRATCH. :wink:

Don, I appreciate your motor expertise and your freely addressing so many technical questions on this board, but it sounds like you may be unfamiliar with this wiring arrangement.

I've had this setup for about 5 years and 300 hrs of operation and I designed and installed it myself following manufacturer specs for each item - it is a standard setup for boats with twin engines that go out in the ocean and is OEM on many new boats. There might be a wiring problem somewhere, but I can assure you that it is not in the electrical system design. If it would be useful I can draw the circuit and parts - I included an image from BEP for this model cluster.

To your specific comments above.

1. each engine has a dedicated starting battery and the positive batteries are never connected together when both engines are operational
---- this is the BEP cluster - http://www.bepmarine.com/en/717-140a-dvsr
---- the yellow parallel switch can be engaged to start one engine, but that is only done if the other engine is off
----------thus, you never have two engines charging circuits connected
----------the switches for the engines are simple on-off switches - nothing complicated
----------the emergency parallel switch is only used if both engines are off, and is disconnected as soon as 1 engine is started
---- all non-motor loads pull from the house battery
--------the house battery cannot draw from either starting battery
--------once a starting battery is fully charged, excess charging capacity is fed to the house battery via the voltage sensitive relay

2. There is a common ground between the two motors and three batteries with large diameter cable identical to the positive battery cable.
---- I have two Blue Sea 600A common busbars that are connected to each other where all grounds connect

3. The BEP emergency parallel switch is specifically designed to be changed while one engine is running. All that the emergency parallel switch does is connect two batteries - switching it while one engine is on only disconnects the extra battery from the running engine and gets that engine back to its dedicated battery. Is there something particular about the Optimax that would make removing a paralleled 2nd battery while running problematic?

My problems manifested prior to any paralleling or any recent changes to the electrical system at all. I should have some solid numerical data after the weekend where I can actually measure max/min values for amperage and voltage at various locations when starting. Fortunately with two engines (one of which is working smoothly) I have ready comparison data, and I'll at least report back what I find based on where it makes sense for me to check.

If you have any input on particular items that I should check on the motor that would be great.

My apologies- I can't makeout the small image you put up for this "BEP" system.

Deal with multi-engine setups quite regularly... many of which are substantially more intricate (electrically speaking)

You initially said that the emergency tie was to be used only when both engines were off... but later indicated it was designed to be used with engines running. ????

See my original post- in order to accurately and cleanly determine that the problems are specific to one branch of the system, you will need to isolate branches (recommend starting with each engine on it's own battery).

While there are several systems vaguely similar to this one on the market- problems DO arise in them.