1977 70hp midrange problems

bbqboat

Recruit
Joined
Oct 6, 2007
Messages
2
Hi. I've been running this engine for quite some time now and all of the sudden I get this problem. It starts just fine and idles like new. I advance the throttle to full and it will accelerate to 3200 rpm with no problem then from there to about 3500 rpm it takes some time to get on plane due to bogging and sounds kind of like the engine is missing. once on plane, it runs like new. This problem occurs about 95% of the time. I have scoured the maintenance Manuel and did the following: Changed the plugs, changed the coils, pulled the reed valves out and they are fine, rebuilt all three carbs, changed the plug wires, changed the fuel filter, changed the fuel lines, and checked the compression (125, 130, 130). I am now at a DEAD END. Oh, one more thing. When I put my boat up on the trailer, I advance to full throttle and the engine will not pass 2500 rpm and sounds like it's just bogging. I have used the same fuel mixture and prop so I can't think those two things would be a factor. I'm dumb founded, any help would be greatly appreciated.
Thank you,
-Will
 

bgbass.1

Chief Petty Officer
Joined
Aug 1, 2007
Messages
558
Re: 1977 70hp midrange problems

i would check the carbs again you have to have all 3 syncronized to work together
 

tashasdaddy

Honorary Moderator Emeritus
Joined
Nov 11, 2005
Messages
51,019
Re: 1977 70hp midrange problems

you either have a high speed jet partially clogged, or need to do a link & sinc.
 
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