2004 - Yamaha F115 - Intermitent Power Loss & Electrical Issue

ruleman

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Jun 11, 2010
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Hello All,

This is my first message here, and I'm trying to diagnose a strange behavior displayed by my 2004 F115 outboard which is installed on a 22 ft pontoon boat.

The boat and engine are new to me, but only had one prior owner who ran the boat in sweet water only (Nebraska) and had 45 or so hours when I got it.

The symptoms are as follows:
Engine ran fine for the first four or five weeks we've had the boat. Revs nicely all the way to 6000 rpms and did not show any signs of issues at all.
This past week however, it began acting up. It would rev up to 4500 or so and then begin sputtering and dying down... it would not put out more than 3500 rpms or even less.

Cruised down to a cove and waited out for a while. Turned the engine off and on again, but the syptoms remained and the engine would still not do anything over 3000 revs. On top of this, when I pulled into the marina, the engine now refused to shut off... turning the key to the off position would do nothing, nor would the kill switch. I had to resort to taking the battery lead out to shut the engine down.

Tried several things after this, like slowly reving up but would not get more than 3000 rpms. After several attempts, the issue seemed to dissappear and the engine ran fine again for a little while (10 or 15 minutes) and then died down again and would not produce anything over 3000 once again. The key shut-off issue continued to appear intermitently during all this time.

I'm confused and puzzled here. I would have thought this had something to do with Fuel starvation, water in the fuel, clogged filter or something similar. Yet, this would not explain the engine's refusal to shut down (which could be independent of the revving issue) making me scratch my head here in disbelief. :confused:

Any hints or ideas regarding this would be greatly appreciated. The local Yamaha dealer says they have a 4 week wait to get to it, and the worst part is that they will not allow me to bring it to them in four weeks, they want us to drop it off and wait out without the boat.

Thanks in advance,
Andres G
 

rodbolt

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Sep 1, 2003
Messages
20,066
Re: 2004 - Yamaha F115 - Intermitent Power Loss & Electrical Issue

last one I had with that symptom turned out to be a bad ECU.
the main relay can do that as well.

bad grounds on the engine can as well.
low fuel rail pressure can cause the loss of RPM.
hope its not an ECU cause they are about 980 dollars.
had one that if you turned the key off idle speed would drop slightly and if you tapped on the ecu it would shut off.
 

ruleman

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Jun 11, 2010
Messages
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Re: 2004 - Yamaha F115 - Intermitent Power Loss & Electrical Issue

Hello Rodbolt,

Thanks for your reply. I will check the main relay first, and if its not that, then I guess I'm in the hands of the local mechanic.

Any ideas if there are used or refurbished ECU units available? I've replaced these before in cars, usually in jeeps that end up underwater for too long, and I've noticed that reprogrammed/refurbished ones are much less expensive than OEM replacements.

Thanks again,
Andres G
 

rodbolt

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20,066
Re: 2004 - Yamaha F115 - Intermitent Power Loss & Electrical Issue

no refurbished units that I know of.
 

ruleman

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Jun 11, 2010
Messages
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Re: 2004 - Yamaha F115 - Intermitent Power Loss & Electrical Issue

Ouch!

I'll hit the main relay first... any hint as to what/how to test it? Also, is there a way to test the key switch that does not involve installing a new one?

Thanks once again,
Andres
 

rodbolt

Supreme Mariner
Joined
Sep 1, 2003
Messages
20,066
Re: 2004 - Yamaha F115 - Intermitent Power Loss & Electrical Issue

with a voltmeter and the wiring diagram in the back of the yamaha F115 service manual.
but I would also verify fuel rail pressure.
 

ruleman

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Jun 11, 2010
Messages
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Re: 2004 - Yamaha F115 - Intermitent Power Loss & Electrical Issue

Hello Rodbolt,

Wanted to provide an update on this as I've heard back from the mechanic this AM. According to him, there are several things gone wrong with the engine and he believes the main cause could be that someone might have messed around with the electricals/battery (maybe connecting the battery leads the wrong way around), generating the issue that damaged the parts.

He mentioned that there is an error on the ECM, the Voltage Regulator and the fuel rail pressure monitor/sensor (TPS?). Also, he suggested there might be a problem with the ignition switch as well.

I have to say I'm a bit puzzled by this, not only because of the prices they quoted, but also by the explanation provided as to how the issue could have been caused in the first place... I've never messed with the battery until the moment in which the engine would not stop, so I am inclined to thiscard that theory, but not just yet.

Anyway, here are the parts the shop says we need to replace:
Mitsubishi ECM ? F8T93175 ? 68V20
Voltage Regulator ? SH678813

I would like to know where I can source these parts as I'm being quoted exactly double of what you suggested for the ECU ($980 vs $1700) and over $1000 for the Voltage Regulator... I've replaced voltage regulators in my cars before and I've never paid more than $150 for one :confused:

The engine is a 04 Yamaha 115 4 stroke ? Engine Serial # 1026550

Thanks in advance,
Andres G
 

ruleman

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Messages
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Re: 2004 - Yamaha F115 - Intermitent Power Loss & Electrical Issue

Wanted to provide a final update. Decided against the first mechanic as he was beating around the bush too much for my liking. Took the boat up to the local Yamaha authorized service and got a diagnostic from them, basicailly identifying voltage regulator as the culprit and ECU as the victim.

Total repair cost including labor will be 1500...

Thanks to everyone here for their help and input.

Regards,
Andres G
 
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