1989 Merc 70 rpms get to about 2300 and never stay the same. Please help

fsmonkster

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May 28, 2017
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It starts fine and runs fine out of the water. When it gets under a load the rpms only get to about 2300 or so. But when going across the lake, which takes some time at 7mph, the rpms will gradually pick up. Never the same one min will be 1900 next 2100. Top that the rpms will get to is about about 2800 on very occasionally. The throttle is fully wide open and not touched. It did get to 23mph one time after 20mins or so coming back across lake. The rpms will slowly go up and back down while running never touching wide open throttle. As my 9yr old says that the motor will not catch up. As soon as you let off and stop all this starts over. I have had all 3 carbs cleaned out, the reed diaphrams redone, everything that I could possibly think of. Somebody told me could be the prop, but wouldn't the rpms rise and not your speed if so? I don't think it would be the coils since it does climb to 23mph and they test fine at home, just don't know how to test under a load tho. Then I've heard it could be the trigger or even the stator. I don't have a clue to how to test either of them. The boat ran fine 2yrs ago then I had to change the reed gaskets, I think that's what it's called, between the carb and block, because gas was leaking very bad. Then while in the process of that family problems came up out of town so that had to wait. It was over a year before I could finish working on the boat. Any help from you guys on what my problem is would be greatly appreciated from me and my son. We can't go fishing every week like we use to.
 
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