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200 mariner low power

E

elit4ce05

New member
I have a 200 mariner that I have had in and out of shops over that past year. It seems I have a problem that comes and goes but right now I think it is here to stay. It cranks fine but, as most of you can, I can tell that it is not right by the 1) it idles maybe 200 rpm less that when it is running right and 2) when you rev it a little ,the RPM's fall off really quick. Now like I said, I have had it in several shops and we have been told that the boat is fine, everything checks out great, but we have only had I person to actually take it out on the lake and run it and when you throttle down it falls on its face and will only manage about 3500 rpms. We were told by this guy it was in the stator/trigger.(eventhough all checks out within specs at the shop. We replaced with new both the stator and trigger,same problem. We replaced both power packs with new,same problem. We replaced reed valves, same problem. Compression is within a few pounds of each other on all cylinders and since this was checked several months back ,I can't really remember the exact reading but they were very close to my merc 200 which I just rebuilt. We have had one retired mechanic tell us it sounded like a fuel delivery problem. We removed the tank, cleaned it out completely replaced filter and all lines, fuel pressure checks out as per manual specs. All cylinders are firing and we have replaced the coils with the ones off my known good 200 and have the same problem. We have replaced the head gaskets on both sides but the old ones appeared fine. Carbs have been removed and soaked for 2 days the completely cleaned and we still have the same problem. Only thing that I notice is after it has idled a while,you can look at the back of the carbs and all are wet except the bottom left barrel. All plugs are wet and when you put your hand over that barrel to block the air it does puddle up fuel to make me think that carb is doing like it should. This boat has always been an extremely fast and dependable boat. This problem first started by it would only happen every now and then and just clear up. Almost like flipping a switch which led us to believe it was electrical. But ALL wiring and grounds have been replaced and still same problem. PLEASE someone give me a suggestion We may have overlooked. Thanks,​
 
What happens if you squeeze the primer bulb when it starts to fall on its face? Did you try an auxillary furl tank?
 
yes we have ran it on another tank and tried pumping the ball as it is running. We replace the pump ball and replaced all the lines. You can pump it up tight and it stays tight pretty much all day. I have worked on these things a long time and I have never ran into a problem like this. Pretty much everything has been replaced with either new or known good. Only part on the engine that has NOT been replaced is the flywheel itself,,but upon inspection it appears to be fine. Like I said, you can find alot of people who will go through the troubleshooting steps as outlined in the manual,and they all say it checks fine,but nobody really likes to mess with problems that just won't go away.
 
You can pump it up tight and it stays tight pretty much all day.
Click to expand...
Kind of a dead give-a-way that enough fuel is not getting thru...it is normal for it to go soft after a minute.
 
Anybody look at the bottom crankshaft seal ??---------Anybody look for issues with reeds or crankshaft seal rings ??
 
Is power trim working like it should ? Mechanic kept saying engine was fine but couldnt get rpms up finally figured out seals blowed in power trim . They wouldnt hold under pressure just a thought.
 
also,replaced main seals this weekend,although they at first glance we were sure this was going to be the problem but after replacing ,it still had the same signs. re-ran a compression test.I know it's not the best but all cylinders were between 113-115.Put my carbs and coils and power packs on together and still had same problems. Would it be possible for the crankshaft seal rings to cause this? Everything on the engine(electrical and fuel) has been replaced.Eventhough we have resealed the engine,we did not plan the heads.Maybe next move.
 
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