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Old 03 June 2009, 01:40   #1
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Loss of port side cylinders on Yam 115 BETO (1996)

Guys,

I've got a Yam 115 BETO V4(1996), been suffering intermittent power loss and whilst bringing the boat up the river the other day I lost power again, took out the plugs and saw that the port side plugs were wet and oily, and the stbd side dry.

Does the loss of just the port side plugs immediatly give any of you guys an idea of what it can be? I initially thought I was losing one and that maybe I had a bad coil - but two at the same time? I'm borrowing a peak voltmeter to check that this weekend.

The sparkplugs are new this season, so is the fuel pump and the carbs were cleaned 4 weeks ago (for the 3rd time!) so i'm pretty happy its not the fuel that is the problem.

So, anyone had this and is it a pointer to an obvious problem?

Got a manual and tools....just need to know which bit to check/fix

thanks

Lew
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Old 03 June 2009, 03:17   #2
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I can tell you of my experience on a 200 Yamaha V Max.

We started intermittantly losing the starboard bank. This pointed to the engine going into 'limp home mode'.

The potentia causes for this were oveheating, (two head sensors) or low oil level in either the engine tank or the boat tank. None of these was the case.

So the next suspect item was the CDI unit. his sells for 1244 plus VAT. Fortunatelywe found someone who had pare and this was tried. Problem remained.

We tested all the coils by substitution and no fault was found.

Next possibility was one of the two pulser coils. No fault here either.

In the end the problem was traced o a faulty stator. The output voltage was down hence the problem.

I realise that your engine is dfferent, but the control circuit may be very similar.
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Old 03 June 2009, 03:21   #3
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Check it's sparking first. It could be the stator or ignition module. Test procedures for those should be in your manual.

Dry plugs aren't necessarily a sign of running on that pot though.
If you're not getting fuel to one side it'll oil up the ones it's running on as you use extra throttle to keep it running . Basically to keep it running, you have to overfuel it which gives you oily plugs.
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Old 03 June 2009, 03:30   #4
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Oddly enough I do have a Yam 115 stator and the bits sat under my desk at the moment, probably looking for a good home.

Pete
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Old 03 June 2009, 06:36   #5
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Pete, I may well take you up on that - can you pm me with price please.

I'll check the stator and ignition module, coils and the earths. I havent got the manual with me at the moment but don't believe its got a guide to checking the CDI except with resistance - is that ok or is there another way to do it, same with the stator and coils, what is the best way to test.

The problem started some time ago with an intermittant loss of power. I'd be running along at full power, 5600 rpm and then it will suddenly drop to 4300rpm. I would stay on the plane and the engine sounded the same but I thought I was losing a single cylinder. This could happen for a few seconds to several minutes but I've never been able to make it happen to fault trace. Hence the new fuel pump etc that i've put in over the last few weeks. Do these initial symptems followed by the loss of the port side cylinders all point to electrical rather than fuel?

I thought it was a coil breaking down but at least this gives me more to test. Thanks very much for your help. Any more ideas please throw them my way!!

regards,

Lew
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Old 03 June 2009, 09:24   #6
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You have done the obvious things with the fuel, so possibly a coil or the stator. You could try changing the coils and leads over to see if the fault moves to the starboard side, and then up and down. Label them first though.

Think you are going to need the full Yamaha Workshop manual to test the stator, mine cost 24 but that was 1995 time and passed it on to Rene with the boat.

PM ref stator on its way.

Pete
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Old 03 June 2009, 10:36   #7
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Thanks Pete,

I've got a Clymer(sp) manual but not with me so don't know if its got the test procedures - will give it a go this weekend.
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Old 03 June 2009, 12:47   #8
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Quote:
Originally Posted by LewisB View Post
Pete, I may well take you up on that - can you pm me with price please.

I'll check the stator and ignition module, coils and the earths. I havent got the manual with me at the moment but don't believe its got a guide to checking the CDI except with resistance - is that ok or is there another way to do it, same with the stator and coils, what is the best way to test.

The problem started some time ago with an intermittant loss of power. I'd be running along at full power, 5600 rpm and then it will suddenly drop to 4300rpm. I would stay on the plane and the engine sounded the same but I thought I was losing a single cylinder. This could happen for a few seconds to several minutes but I've never been able to make it happen to fault trace. Hence the new fuel pump etc that i've put in over the last few weeks. Do these initial symptems followed by the loss of the port side cylinders all point to electrical rather than fuel?

I thought it was a coil breaking down but at least this gives me more to test. Thanks very much for your help. Any more ideas please throw them my way!!

regards,

Lew
Unfortunately a CDI can emulate almost any other problem while failing (I once had a bike CDI unit go and cut out #2 and #4 pots when the coils fed 1+4 and 2+3). I reckon it's a good place to start,along with the stator. Get your multimeter out
Realistically, it still could be anything-but that's where I'd start.
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Old 03 June 2009, 15:22   #9
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check your voltage OUTPUT off the CDI unit . u will see your stator AC wires coming in and then on the other side of the box you will see the ( i think ) the black with a white tracer going to the ignition coils . test off that point on the CDI .U should get 150 - 250 volts off that . If nothing then switch the wires over from the other bank and see what happens . If still the same off those first points u tested then CDI . I have replaced a few of them . hope this makes sense .
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Old 03 June 2009, 16:55   #10
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Outboardtech, thanks, I wont be able to do these test till the weekend but i'll report back.

I assume the clymer manual will state how to do the test properly, to test the CDI I guess that the engine has to be running, is it ok on the muffs or should it be in the tank (sea in my case!) to give it decent backpressure?

cheers,

Lew
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