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Old 07 August 2008, 07:54   #1
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Country: UK - Scotland
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2004 Mariner 75 - 2 stroke, with a limp!

After a days cruising the following noted;

1. Engine will not rev to any more that 3000 rpm.
2. Engine runs rough and faltering on idle.
3. Bottom plug cold, others appear normal in temperature.
4. Fuel consumption high in these circumstances.
5. Spark at bottom plug healthy, plug changed for proven functioning plug.
6. Bottom plug wet, unleaded fuel supply adequate.
7. Air and small odd particles of foreign “brass” material noted within integral oil supply pipe.
8. Oil reservoir noted consistently over 50% full (with branded Quicksilver product) for duration of days cruise, and at all times prior.
9. Prop or inlets/outlets not fouled.
10. Engine has been consistently smoky on starting from new, albeit considered a consequence of lengthy lay-up periods.


Any inexpensive advice on getting it diagnosed or even sorted (engineers report to Mariner?)? the retailer of my out of warranty engine is 300 miles away.

Sadgit
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Old 07 August 2008, 08:03   #2
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Mariner with limp

Sorry - forgot to add THE most important bit, its only run 30 hours! in all the time i've had it from new.
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Old 07 August 2008, 08:32   #3
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You say there is a healthy spark, so ruling that out and adding to the smoke it sounds like it might be over fuelling on the bottom cylinder. That would certianly cause smoking & lumpy idle. Bottom carb would be my first port of call......

Is it a 3 cyl? I had a 25 suz 3 cyl wouldn't do much more than that with one cyl "dead", my current 55 is a 2 cyl and if one dies I might as well have a seagull on the transom for all the power that gets to the prop! One dead cyl the engine still has to use the power from the other cylinder(s) to compress the air in the dead one. Having compressed said air, you get next to nothing back - so output drops, but by more than 1/3 as it;s not just "simply" removed.


As for your oil pipe, I'd get that flushed (along with the rest of the system). if you have solids in there you'll certianly know when it blocks one of the jets! if there's still air bubbles run a tank of premix through to protect your engine - it'll smoke like the proverbial bandit, but at least it won't sieze. Once the system is bubble free, switch back to neat fuel.


When you say 30 hrs from new, you do mean since you got it or an absolute grand total of 30 hrs? (and was it running OK before?)
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Old 07 August 2008, 08:46   #4
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petrol pump diaphragm

split diaphragm will flood bottom cylinder cheap and quick to fix
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Old 07 August 2008, 11:10   #5
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Quote:
Originally Posted by doggypaddle View Post
split diaphragm will flood bottom cylinder cheap and quick to fix
Thanks all for the responses so far, cheered me up no end!

What would cause a diaphragm to split? running out of fuel at speed?

The engine was brand new to me and rigged with boat and both have 30 hours Grand total.
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Old 07 August 2008, 13:32   #6
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i dont think running out of fuel at full speed would cause a diaphragm failure as such, but i suppose its possible that if it was a bit dodgy anyway the sudden extra movment pumping air rather than fuel could cause it to go. it certainly well worth checking. on the yamaha it was obvious once the assembly was removed, squeezing the bulb hard caused fuel to pour out of the hole that feeds into the crankcase. its only held together with a few screws it really is a 10 minute job.
Have you checked compressions yet? to see that the offending cylinder isnt low?
I wouldnt worry if its a bit down bound to be after all the unburnt fuel sloshing around but shouldnt be more than a few 10s of psi different. they can get surprisingly low before a missfire shows up.
If you have conpression, and a good FAT spark, and the pump diaphragm is OK, then move on to the carb, check needle valve action IE it isnt flooding the carb associated with that cylinder, and check the main jet hasnt dropped into the float Chamber.
compression test should show up a headgasket problem,only other thing i can think of that springs to mind is the exhaust plate where coolant and exhaust mix, if these rot through you can get a missfire due to water in the cylinder.
if its none of these maybe swap coils around to see if the missfire moves? but its a long shot if there is a really fat spark, but they can fail under load as can cdi units and pickups.

let us know how you get on>
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Old 07 August 2008, 15:50   #7
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Sounds like its dropped a cylinder, you need to identify which one it is. If you have three big sparks, then the next easy thing you can do is remove the attenuator cover (black plastic cover that covers the carbs) 6 self tapping screws. Get a big rag run the engine up to about 1500rpm and bloke each carb in turn the engine should bog down and possibly stop all together. If one carb has no effect i would suggest it will be a carb fault which would need looking at.
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Old 09 August 2008, 13:21   #8
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Originally Posted by Turbodiesel View Post
If one carb has no effect i would suggest it will be a carb fault which would need looking at.
Or the fuel pump diaphragm
or no compression
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Old 12 August 2008, 11:11   #9
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Originally Posted by doggypaddle View Post
Or the fuel pump diaphragm
or no compression
Low compression, if its stopping it from reving up, you would probably hear it rattle like hell. Fuel pump diaghragms usually just drop rpm until it stops running, just prime the bulb and if it revs back up, change the pump!. But worth checking compression first as its easy to check!
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Old 12 August 2008, 14:24   #10
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fuel pump diaphram will cause a missfire too........ a small split can fill the crank case with fuel flooding the cylinder to which the pump is attached, long before the pump stops pumping. my yamaha had a missfire on the bottom cylinder and john flood at flood marine said thats the first thing to check- he was right too, but in my case the pump was just falling apart!

come on put us out of our misery....fix it and tell us what the problem was
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