1970 7.5 Merc runs better with cover off ????

[bluemonster1]

why would the motor run good with cover off? Put cover on and she starts smokin more and throttle response is terrible to boot. I had issue's with this motor earlie around March/April where it wouldn't idle and just stopped running and didn't rev up well.Since then I bought another used 7.5 motor..took stator from it to the first motor.To my surprise she is now running good.Idle is not a issue anymore and revs up pretty smooth.Carb has been out 3 times,cleaned and new gaskets.Fuel pump was rebuilt and new pump cover replaced because of a crack in old one.New gas line bought and gas tank cap air bleeder working,even tried with cap loose and off even.I did link and sync as per manual,breaker points are good and re-gapped to .020 as per manual.New plugs installed,wires all good also.

Now why when I put the cover on does it lose its power.I know cover is completely sealed all around when locked in place.Then how does the carb get its volume of air at higher speeds??Throttle can be cranked to the end and no increase in rpm.Take cover off and throttle is responsive from idle to end..go figure.Some one on here must have a clue what the heck is going on here...please help me solve this as it is driving me CRAZY!!! Does not make any sense to me..what am I missing here.

 

[JB]

Re: 1970 7.5 Merc runs better with cover off ????

Check the ventilation of the cowl and check for an exhaust leak inside the cowl, monster.

Good luck.

 

[bluemonster1]

Re: 1970 7.5 Merc runs better with cover off ????

well I feel dumb.....but read other posts where guys had same issue.It was the friggen exhaust in the barrel.I didn't cut the barrel out totally round since it had a solid top on it.I cut just enough for the motor to drop in..it was then retaining exhaust that was swirling around.Then I found out where the intake grill for the air was,bottom of housing same side as shift lever..directly below.NEVER NEW THAT..dah!.Hey newbie here.what more can I say,live and learn.At least I solve my issues eventually..