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1982-83 mercury 70hp bogging down at wot

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Redrider6604

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The boat it’s on is a 17’ deep v hull boat. On a good day it might hit 23 mph with two people. But it’s great for just cruising around for us. Last year we were out on the river and ran great. Had it off for a while we floated with the current. Started back up and idles perfectly fine. Went to go give it wot, it would bog down and it would try to open up but it just couldn’t. So got back to the ramp and took it home and parked it. Rebuilt the carbs once again thinking that was the problem but they were spotless inside but rebuilt them anyways using oem gaskets and stuff. Rebuilt the fuel pump and replaced all the fuel lines and the primer bulb to the tank. I have replaced all three coils last spring along with the ignition box also. Plugs are new and wires also. Has good compression on all three cylinders. I have even took the gas cap off while trying it and it didn’t help either. But it idles great in the water and if I throttle it up manually in neutral, it revs all the way up with no problems but when it’s in gear, goes fine till you try to go wot then it Boggs down really bad. Any help is greatly appreciated!
 
Could be running on 2 of 3 cylinders.----Check for STRONG spark on each lead.-----What are the actual compression values?----Boost venturis in place ?----New water pump impeller every 5 years >---Broken / stuck open reed valve?
 
racerone said:
Could be running on 2 of 3 cylinders.----Check for STRONG spark on each lead.-----What are the actual compression values?----Boost venturis in place ?----New water pump impeller every 5 years >---Broken / stuck open reed valve?
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The motor had very good compression when I checked it when I had the problem last year. All three were close in range. I believe they were right around 150 or so. But all were acceptable. Yes the venturis are tight and not loose. I do have new ones to go in but couldn’t figure out how to remove the center jet. Water pump was replaced last summer also and I’m not sure about the reed valves on it. The motor was gone though supposedly before I got the boat but the boat sat for about 10 years. What is the best way to check the reed valves since they are located on crankshaft?
 
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