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High RPM Running Issues

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Gracing76

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I have a 1987 Mariner 60hp, 3 cylinder, 2 stroke outboard. It's mounted on a 1987 Bass Tracker boat, this is an all original set up. It was given to me by my grandfather, that's owned it since new and always had to professionally maintained. It has been sitting for the past 5 years in storage, it was professionally winterized before storage. Anyway, my issue is that I cannot get it to run over 3,000 RPM's. It starts right up and idles fine, it also runs good up until 3,000 RPM'S but then just sits there and won't go any higher. It doesn't cut out or anything. I can't even really get my boat to plain off with me and another person. All of the spark plugs look good and there all firing, they were replaced when I got the boat from my grandfather. I replaced the water pump impeller, cleaned the carbs (they were not clogged at all, all of the fuel was removed before storage), I replaced the fuel water separator filter and the fuel line from the tank to the outboard. I've tried two different fuel tanks and the engine ran the same so I know it's not the tank. I am going to rebuild the fuel pump either tonight or tomorrow and replace the fuel lines under the power head cover, but I don't think that they are the issue. I tried pumping the fuel line bulb while running and it still would not run over 3,000 RPM's. I checked the throttle linkage and it is going to WOT when pushing the throttle lever all of the way forward. I read that some of these outboards have a two stage stator but I believe the 1987's do not. So what should I be looking at next?
 
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See if the BOTTOM carb is opening when the TOP one does. There's a whimpy black plastic linkage between the carbs that may be broken or not lined up correctly.

Jeff
 
fastjeff said:
See if the BOTTOM carb is opening when the TOP one does. There's a whimpy black plastic linkage between the carbs that may be broken or not lined up correctly.

Jeff
Click to expand...

Thanks for the reply. All of the linkages and cables are good. I recently had the carbs apart to clean. I wish I would have just replaced the fuel lines then but didn't have the correct size hose at the time. Thanks.
 
Well I did some tinkering and made things worse... I ohm tested the rectifier and found that it was bad. I replaced it with a brand new one and the engine started just as before. This time when taking it to wide open throttle it actually started to gain RPM'S and then as of some one flipped a switch my engine just died and took a while to restart. Now when you put it in gear it just dies. If I put it in neutral and Rev it up it seems to run fine, but I have to feather the throttle and raise the prop almost out of the water to get going or it dies. I went ahead and replaced all of the fuel lines and rebuilt the fuel pump. After doing that I took it out again with the same results, such as dieing when putting it on gear. Now I think that I'm only running on the number 2 cylinder. While the engine was running I pulled the plug wires one by one. Absolutely no spark from #1. Pulling number 2 kills the engine and pulling #3 doesn't change the way that the engine is running but it is still sparking. I don't believe that the engine is running off of cylinder #3 even though it is sparking. I ohm tested the coils and they all checked good, the rectifier is brand new, the stator ohm tests good and all if the wires are hooked up perfectly. It's hard for me to just run down and put my boat in the water to check things while it's running because I live 30 minutes from the river but is there anything I should be checking next?
 
Okay. If the plugs are getting spark, and the timing is okay (probably) but that cylinder won't run, then it's either not getting gas from the carb, or the reeds/ seals/ etc. are not allowing a fuel air mixture to form and be pushed into the combustion chamber. That's all there is to it.

Assuming that's the older Merc triple, with two carbs, a few things can be eliminated: IF the reeds were bad, the top and bottom would be effected as well since they share them. (Cylinder # 1, for example, breathes through the top reed assembly, as does cylinder # 2. With the lower with the lower reed assembly, cyinder # 3 and # 2 breath through the lower reed assembly. It's a weird deal.)

That leaves us with seal problems. It's POSSIBLE--since # 1 and # are the only ones effected by a bad seal--that they MIGHT be the cause, but I'm a bit doubtful: never seen a seal go that bad. That said, I'd replace the top seal (easy to do) and see if that helps.

Sorry I couldn't be more help.

Jeff
 
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