Pontoon Boat & Deck Boat Forum

I have had a starting problem with my 90HP Mercury 4-stroke too... here are the facts:
1. About 120 hrs on the motor (2005) - 40 of them since Sept 1
2. Stopped the motor to watch the sunset and take photos, engine would not startup afterwards. No sound, no nothing
3. Nav lights worked fine - but I think were quite dim
4. Connected a batter charger while everything was connected. After appearing to charge for a brief time, used the remote trim up (on the Quicksilver console) and it operated briefly then quit.
5. Removed battery and put a charger on it overnight - didn't seem to be taking a charge (although now when I think about it it may've been charged - never tested it w/ a voltmeter
5. Replace the battery and no go. This time, not even the nav lights (and things that are normally on in the OFF position weren't there)
6. Inspected under the console - found a black wire with some melted insulation and bare spots... it's one of the wires coming from the ignition harness.
7. Ordered and installed replacement harness - and connected it across the deck of the boat (just to confirm that was it)
8. Still no go. Can't even use the cowl or remote trim up/down - as if there's no +12V power.
9. Fuses (all that I've found, anyway) - check fine. Several withing the starboard side's electrical panel - and one on the +12V connection at the battery. (there are two other connections in parallel - black wires with no apparent fusing).

I've got all of the test gear I think I need (test light, voltmeter, ohm meter)... and am reasonably confident in reading a wiring diagram. It's tough sometimes though to make sure I've found the right part on the motor.

Finally found a Mercury manual on-line,so that's been great help.

Q: Are there any hidden fuses or something that may be bad and I can't see?
Q: Suggested next steps?
Q: Are the relays (starter and 2 trims) what I see right below the series of fuses at the top of the electrical panel?



Thanks in advance.

I split this post ...

No hijacking

Did you check the fuses on the motor? There are small fuse blocks under the motor cowl on the starbord side of the motor. I had a similar problem on my 90 this summer after I was messsing around under the console and grounded out a wire by accident and it was a fuse on the motor.

Yes and they all checked OK.

I think there were about 5 of them - some 20a and some 30a. Several of the sets were paired - I'm pretty sure one in each such pair was a spare, though. (checked ALL of them)

Thanks for the tip. Wish that's what it was...

Their are at least 2 fuse blocks on the motor, and the one that was blown on mine was a 15 amp in the upper block.

Check your ground. Follow the cable from the Battery back. It sounds as though you are over thinking this one.

Ghost Rider - I did check for continuity between the battery ground terminal and the terminal below the starter - and it was fine.

I'll recheck just for certainty, though.

I'll report back later today/tonight about my findings.

Thanks.

Ghost Rider was right - I maybe over-complicated this one. I now think that I haven't been putting the cable to the battery to the proper terminals.

Before I go and ruin something - any comments from the experts here on my analysis?

Thanks in advance.

worst case senario, some of those symptoms smell of a failed ECM. I know on Etecs the trim and all motor power is run through or supplied from the ECM.

In your last picture, the green circled area has a Pos cable end AND a neg cable end laying up against a bulkhead. Have you been hooking that one up? Easy to miss................

@parasympathetic - yep, I now am sure I have the battery connected properly. Accessories that are available without "RUN" work (nave lights, horn, stereo, lights for gages).

Neither trim switch works in either UP or DOWN positions, and nothing happens in the START position. The only common thing I can see is the 30A fuse in that circuit. Gotta double/triple check that today.

I'll also check my wiring diagrams to see if the ECM circuit is common. Not sure where that's physically located.

Guess I'm closer....

Okay, Before you said nothing at all worked. Now you have accesories, This is good. I think you may have hooked the battery up wrong and blown a fuse. My Merc four stroke has a 20 amp fuse that blew once when my kid did the same thing. When that happened I could not get anything at all. Just like you are experiancing. I would pull every fuse and recheck.

And make sure you've got a good strong battery. Wouldn't hurt to load test the battery.

I don't think this has anything to do with my issue... but it's tucked next to the starter relay within the electrical compartment on the starboard side (below the fuse holders).

Any idea what it is?

SUCCESS!

Thanks for the help... but it was really a bonehead (but learning) experience.

Here's what I assume the deal is/was:
1. Battery went bad - when removed would not accept a charge
2. Replaced battery, but didn't hook up the cables properly
3. Once the cables were correct, was able to get the accessories to work (those not needing the RUN position)
4. Trim UP/DOWN nor START would work - so tracked it down to fuse issues
5. Found that when I'd checked fuses early on, I didn't insert the upper 20A fuse correctly - which was the issue.
It's inserted correctly and appears to have solved the problem.

Bad news - I missed a week of great autumn boating weather
Good news - I learned about the boat's electrical system and... I'm back in business without any service calls.

This forum is awesome!