Running engine with hatch closed

[K. Merson]

Have a 9.9 Yamaha 4 stroke. The engine appears to get starved for air when I close the engine hatch over the well. It particularly becomes noticable when I am running at low RPM. What happens is the engine drops RPM and sounds like it is gonna stall. As soon as I open the hatch it runs normal. Had a 4-stroke Honda 10 hp and did the same thing. Anyone solve this????



kmerson@avaloninternet.net

[bill willis]

Have a 9.9 Yamaha 4 stroke. The engine appears to get starved for air when I close the engine hatch over the well. It particularly becomes noticable when I am running at low RPM. What happens is the engine drops RPM and sounds like it is gonna stall. As soon as I open the hatch it runs normal. Had a 4-stroke Honda 10 hp and did the same thing. Anyone solve this????

Yes, I solved the problem on my CD25. The only air inlet on my outboard (5hp Honda) was on the bottom side of the motor head, and the air down there gets fouled by secondary exhaust. I discovered one day that by running the engine with the engine cover off and the hatch closed, it would run fine with no stalling or starving. To solve the problem I cut approx. 3" and 4" dia holes on the cover and fitted them with round louvered ss locker vents from West Marine. (They come in two sizes and I used the sizes that best fit each surface.) Ended up with two vents on each side and one on top of cover for a total of five vents. The engine now gets sufficient fresh air through these vents with the hatch closed. I also attached a piece of small dia copper tubing (glued with 3M 5200) running from the secondary exhaust down the motor shaft and under water. This solved the build up of any exhaust fumes in the well. I know this works on 5 and 8hp Hondas...It should work on your Yamaha. To test it, try running with hatch closed and motor cover removed. You should see an improvement.
Good luck,
Bill



wawillis@toad.net

[Al Levesque]

...The engine appears to get starved for air when I close the engine hatch over the well....

There was some discussion about this a while back that should be available from archives.

We solved the problem in our 6hp Evinrude by plugging the upper exhaust vent. This forced the exhaust down to the lower exit under the water. Ran for countless hours with the hatch closed and never a problem.

Al



albertlevesque@cove.com

[Kurt]

with my 9.9 Honda I cut a 2" hole in the engine cover and mounted a plastic thru hull fitting to the hole...then I ran a 2" flexible hose up to one of the engine hatch vents and wired it in position...I also plugged up the original idle relief port and fabricated a new one utilizing a brass elbow and short piece of flexible tubing that I ran outside of the engine well near the water line...works great



kjlgpw@aol.com