faulty outboard

[rubbishman]

Hi All, I have a Mariner 6hp twin,2 stroke.Starts OK,idles fine,very smooth right up to WOT.Then after 10-15 mins gets lumpy ,no power.Tried pumping the bulb,putting choke on,unscrewing filler cap, no change!Water jet goes on and off as it should.No petoil leaks I can see.Stripped carb right down looked ok to me.BTW new plugs,fuel,oil.When it is running rough I've knocked it off at wot and one plug is black.So I'm thinking its one of the coils but I don't know of course.Could it be the CDI?Any thoughts appreciated. p.s. leave the thing an hour or two and its fine for 15mins run time.

 

[VicS]

Hi All, I have a Mariner 6hp twin,2 stroke.Starts OK,idles fine,very smooth right up to WOT.Then after 10-15 mins gets lumpy ,no power.Tried pumping the bulb,putting choke on,unscrewing filler cap, no change!Water jet goes on and off as it should.No petoil leaks I can see.Stripped carb right down looked ok to me.BTW new plugs,fuel,oil.When it is running rough I've knocked it off at wot and one plug is black.So I'm thinking its one of the coils but I don't know of course.Could it be the CDI?Any thoughts appreciated. p.s. leave the thing an hour or two and its fine for 15mins run time.

Tried disconnecting the fuel line? Just to see if the trouble might be flooding.

You don't say the age or the serial number but you imply that it's a model with two separate coils. Try swapping them over to see if the problem moves with the coil or stays on the same cylinder.

Need to check the sparks when its misbehaving really with in line spark testers. If it is not plugs and not coils its likely to be the CDI if there is a problem with sparks

Should the water telltale go on and off. I'd expect a constant stream....... Are you sure there is not a cooling problem leading to overheating.

 

[rubbishman]

Hi VicS, thanks for replying.I will try fuel line disconnect tomorrow.Re swapping coils,one ht lead is too short I will try to lengthen somehow.Serial number is 09956089.Don't know what a in line spark plug tester is?Re telltale,some models had a thermostat and to quote the handbook"the amount of water flow can vary due to thermostat operation"I guess they thought it makes it more efficient.Seems just another thing to go wrong to me and all the other outboards I've had ,had a constant stream as you describe.

 

[VicS]

Hi VicS, thanks for replying.I will try fuel line disconnect tomorrow.Re swapping coils,one ht lead is too short I will try to lengthen somehow.Serial number is 09956089.Don't know what a in line spark plug tester is?Re telltale,some models had a thermostat and to quote the handbook"the amount of water flow can vary due to thermostat operation"I guess they thought it makes it more efficient.Seems just another thing to go wrong to me and all the other outboards I've had ,had a constant stream as you describe.

I make that a Belgium built 1997 model.

The water flow from the telltale can vary but once up to operating temp I'd expect a continuous stream, variable perhaps but I'd be suspicious if it stopped altogether. The engine is mounted deep enough for the water pump never to be starved of water ??

The in line spark testers are this sort of thing http://www.ebay.co.uk/bhp/ignition-spark-tester

AFAIK the coils and HT leads are separate parts so swapping the coils should be possible.

Also look critically at the HT leads

 

[JumbleDuck]

The in line spark testers are this sort of thing http://www.ebay.co.uk/bhp/ignition-spark-tester

The most useful ignigtion diagnostic tool I have by far is my Gunson Flash Test:

Unfortunately they don't seem to make them any more, but they are well worth looking for secondhand.

 

[macnorton]

Use a strobe light to check the spark, you can check the internal resistance of the coil with a meter, quite often a coil that is failing will last longer with the hood off due to better cooling.
cdi pickups usually work or not but ignition modules can give intermittent fault.

 

[rubbishman]

Hi all, thanks for all replies.Bl...dy thing is worse now.Swopped coils round, swopped plugs round.Top cylinder plug wet (flooded?).Bottom cylinder plug black,dry, sooty(rich?).Won't idle at all now and is rough on half or full throttle.Disconnected fuel line as suggested and yes it runs quicker for a short time but Don't most engines speed up before they fuel starve?Tried new HT leads.I'm thinking that after second carb stripdown I've messed up somehow on reassembly.But that doesn't explain why cly 1 is wet and cly 2 is sooty.

 

[rubbishman]

Hi all,so as you can see two months have passed and outboard is still the same Ican't fix it and neither can the nice outboard mechanic.He says its very strange!To recap the plugs, leads,coils etc have all been swopped around in every possible way.Compressions are good for both cylinders.I would say that after 5 strip downs of the carb by me and 2 by mechanic it revs a little better but no way is it OK.The strange bit is as always the bottom plug gets black and sooty where as the top spark does not.Any comments would really be appreciated.

 

[Rigger Mortice]

If that model has a fuel pump check that the diaphragm has not gone "baggy".

 

[rubbishman]

OK will do,thanks