Johnson 115hp Air Flow problem

I have a 1973 Johnson 115 that I have put on a 1996 Four Winns w/ a blow Johnson 115. I used the 1996 mid-section and engine cover (so I could have tilt & trim) My problem is that there does not seem to be enough air getting to the carb. The motor revs very high with the cover off, then will die when the cover is put back on. I dont see anywhere for air to get inside the cover, except through the small opening around the exhaust cover. I also have to take the cover off and spray starting fluid into the carbs, for cold starts, even w/ the choke locked open. This model Johnson does not have an adjustable air/ fuel mixture adjustment, They have the high and low oravices. Any thoughts or suggestions appreciated.....

Re: Johnson 115hp Air Flow problem

exhaust leaking from the midsection, back in to the cowl.

Re: Johnson 115hp Air Flow problem

When I did the swap, I didnt have a powerhead gasket and used silicone. That would explain my problem in the area of the midsection.

Re: Johnson 115hp Air Flow problem

You have a mismatch of parts. Check your cowlings. The 71 lower cowling is vented at the bottom for air intake. The 1996 lower cowl may be solid, or non-vented. Those 1996 engines get their fresh air from the vent at the top of the back of the upper cowling. You can remove that upper cowling hand grip and check to be sure it is open for airflow.. Also, in some of these years, the upper cowlings had factory horzontal air vents to improve airflow.

Re: Johnson 115hp Air Flow problem

chacha said:

I have a 1973 Johnson 115 that I have put on a 1996 Four Winns w/ a blow Johnson 115. I used the 1996 mid-section and engine cover (so I could have tilt & trim) My problem is that there does not seem to be enough air getting to the carb. The motor revs very high with the cover off, then will die when the cover is put back on. I dont see anywhere for air to get inside the cover, except through the small opening around the exhaust cover. I also have to take the cover off and spray starting fluid into the carbs, for cold starts, even w/ the choke locked open. This model Johnson does not have an adjustable air/ fuel mixture adjustment, They have the high and low oravices. Any thoughts or suggestions appreciated.....

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Welcome to iboats.

STOP using Starting Fluid! It is a sure method to hurt or destroy a 2 stroke motor. It lacks any lubrication and washes off any lubrication that may be present on your rings and bearings.

Re: Johnson 115hp Air Flow problem

I think I have a bad ingition coil. They all have cracks and one is very shinny (getting hot). A new coil may fix the starting problem, but would it effect the idle problem? I replaced the power pack last year and never got to the coils. The shiny one has recently leaked onto the cylinder head cover.

Re: Johnson 115hp Air Flow problem

Every body was right. Replaced all 4 coils to solve the starting problem. The engine was dying due to the Rear Exhaust Cover covering up the tell tale, (thus the exhaust fumes being trapped under the hood cover, and choking the engine). Cut away a portion of the Exhaust Cover and drilled a few holes under the hood cover handle, for more air to enter. Works great now, Thanks for the help.