1996 mercury 9.9 outboard, stalls when decelerating

[Mc Tool]

I picked up a 6 HP Johnson for next to 0 beer tokens.----Tag says ---" low compression " ----as reason it was set aside.------I tested it at 90 PSI.-----Doubt there is an issue.-----These motors have a hole above exhaust ports.-----Bleeds off compression at low speed.-----Makes for smoother running.----This has fooled more than one person.

I thought the hole above the exhaust port was to act as a decompressor at cranking speeds , if anything it would make the idle worse .
2 stroke compression figures ( like 9.5:1) are static figures ie ,if you do the maths , in motion the effective comp ratio depends on the porting to some degree. At cranking speeds you have to wait untill all the port windows are covered by the piston before any compressing happens , at faster speeds the fuel mix is delivered via the transfer/bypass ports to the combustion chamber at a partially compressed state and the effective comp ratio goes up and thusly some engines will tolerate a lower static comp reading and still run fine . Typically a 2 stroke with to lower comp will be a pig to get to idle /off idle properly and will probly be a poor starter.....particularly when hot .
At the end of the day you are the judge on that , If your happy with the way it starts and runs then it has enough compression

 

[racerone]

Compression in 2 strokes is a confusing subject I think.

 

[Mc Tool]

Compression in 2 strokes is a confusing subject I think.

Yep , both above and below the piston

 

[flyingscott]

I thought the hole above the exhaust port was to act as a decompressor at cranking speeds , if anything it would make the idle worse .
2 stroke compression figures ( like 9.5:1) are static figures ie ,if you do the maths , in motion the effective comp ratio depends on the porting to some degree. At cranking speeds you have to wait untill all the port windows are covered by the piston before any compressing happens , at faster speeds the fuel mix is delivered via the transfer/bypass ports to the combustion chamber at a partially compressed state and the effective comp ratio goes up and thusly some engines will tolerate a lower static comp reading and still run fine . Typically a 2 stroke with to lower comp will be a pig to get to idle /off idle properly and will probly be a poor starter.....particularly when hot .
At the end of the day you are the judge on that , If your happy with the way it starts and runs then it has enough compression

Lower compression engines tend to idle smother

I thought the hole above the exhaust port was to act as a decompressor at cranking speeds , if anything it would make the idle worse .
2 stroke compression figures ( like 9.5:1) are static figures ie ,if you do the maths , in motion the effective comp ratio depends on the porting to some degree. At cranking speeds you have to wait untill all the port windows are covered by the piston before any compressing happens , at faster speeds the fuel mix is delivered via the transfer/bypass ports to the combustion chamber at a partially compressed state and the effective comp ratio goes up and thusly some engines will tolerate a lower static comp reading and still run fine . Typically a 2 stroke with to lower comp will be a pig to get to idle /off idle properly and will probly be a poor starter.....particularly when hot .
At the end of the day you are the judge on that , If your happy with the way it starts and runs then it has enough compression

Decompression holes make the idle smoother.

 

[Texasmark]

A---" crossflow "-- has a deflector on the piston crown to direct incoming charge to scavenge the cylinder.-----A looper has a flat / nearly flat crown and intake ports positioned to loop the incoming charge.

Plus the Looper has a tuned, reflective exhaust function where the exhaust from one cylinder helps to keep the raw fuel in the combustion chamber of a cylinder as the piston is closing off the exhaust port before the big bang. Initially that came to being with the OMC, Evinrude, Trump 3 cyl. 55 HP engine as at the time 3 cylinders were required to get the correct exhaust reflections to make it work. Over time designers figured out how to get 2 and 4 cylinder engines do function properly....have no idea what that took.

My experience with both types of engines is that the cross flow was bullet proof in a lot of situations except for gas consumption. Loopers run circles around them hands down in that accord. But loopers have their differences that have to be dealt with....in my experiences with half a dozen crosses, and later half a dozen loopers. If the cross had the efficiency of loopers I would prefer the cross.s.......my opinion.....and everybody has one........