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Old 27 August 2010, 07:24   #1
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post service lower revs

Hi

I had both my engines serviced by a Mariner dealer and since coming back, on the few times i have been out and at WOT the engines have both seemed to run around 500rpm below what they were before the service (5000rpm now as apposed to ~5500rpm before).

Could it just be that the new spark plugs are giving a more accurate reading to the rev counters? They both seem to be running smoothly enough.

Any ideas

Cheers
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Old 27 August 2010, 07:38   #2
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Hi

I had both my engines serviced by a Mariner dealer and since coming back, on the few times i have been out and at WOT the engines have both seemed to run around 500rpm below what they were before the service (5000rpm now as apposed to ~5500rpm before).

Could it just be that the new spark plugs are giving a more accurate reading to the rev counters? They both seem to be running smoothly enough.

Any ideas

Cheers
Has your speed at WOT changed?
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Old 27 August 2010, 07:45   #3
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yes its dropped by between 1.5 and 2 knots.
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Old 27 August 2010, 08:27   #4
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You havent got more fuel/weight on board than usual, or more weed on the hull? Water under the deck?

I wonder if he's replaced anything on the throttle linkage or cables etc and it its adjusted differently?
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Old 27 August 2010, 09:24   #5
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hi,

nope, no difference in loads etc, as i said they seem to run fine, smooth just seem to not rev as far.

I have noticed they are both smoking a little bit more, but as they both were about the same amount i guessed it was fuel related. I addded 5L of premixed fuel to the 80L fuel tank. But ive used around 80L since adding the premixed fuel. Can you adjust the fuel / oil mixture on the engine or are they auto mix?

I should add they are both 2 stroke oil injection Mariner 60's which is why i didnt think the little extra of oil going into the fuel tank via the premix fuel would matter. Surely the worst that would happen is that the plugs get oiled up a little.
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Old 27 August 2010, 11:05   #6
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I have noticed they are both smoking a little bit more, but as they both were about the same amount i guessed it was fuel related. I addded 5L of premixed fuel to the 80L fuel tank. But ive used around 80L since adding the premixed fuel.
Ok, in theory you should have burned off or "pumped through" any excess oil. I assume your 80L has been at reasonable speed and not cruising about at idle? Pull a spark plug out, & see how manky it is.


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Can you adjust the fuel / oil mixture on the engine or are they auto mix?

I should add they are both 2 stroke oil injection Mariner 60's
Nope, other than adding more oil to the fuel. Not sure how old they are, but early auto mixing basically gave you an accurate, constant 50:1 (instead of all the guddling around wth measuring jugs at the fuel pumps) Modern ones use a mechanical pump that is driven from the crankshaft, so are variable ratio (don't need as much oil at idle, so by cutting the addition of it, means you don't oil your plugs up)

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which is why i didnt think the little extra of oil going into the fuel tank via the premix fuel would matter. Surely the worst that would happen is that the plugs get oiled up a little.
Yep. At the extreme, when you run them in you put about 110L of "Seagull mix" through, and it burns off pretty quickly when you revert to standard.

Might be worth pulling the lid off the air intake boxes & checking that the butterflies are opening fully. If so, I wonder if your spark has been retarded slightly?
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Old 27 August 2010, 12:20   #7
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Ok, many thanks for that.

The fuel was burnt over various of engine speeds, so not mainly at idle. They are late 90's 2 strokes so probably one of the last 2stroke models that Mariner made other than Opti's.

Adjusting the retardation of sparks is beyond my ability but i have removed the plugs and although did have oil on i didnt think they were too bad.

The dealer did change the type of plugs as he said the new ones were the right one for this model. (apparently mariners were either built in Canada, Belguim or Canada/Belguim and each use diff plugs). I have asked a friend who is a very knowledgable car mechanic and he didnt think this would reduce the revs. I will ask him about the spark retardation when i next see him.

Thie drop in revs isnt an issue that i know of, just a bit puzzling.
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Old 27 August 2010, 12:27   #8
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I would say that the throttle linkage has been adjusted or simply disturbed during the service, just a guess but worth a look.
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Old 27 August 2010, 14:52   #9
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engines

hello , whats the serial numbers of the Unit's ??? , Hp ??? , lets have this info and see if there are any service literature , recalls etc etc
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Old 27 August 2010, 15:57   #10
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outboard tech pm sent thanks
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