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Shop Talk > Mokai ES-Kape

Air Shroud and Engine Cooling

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I've been trying to squeeze as much as I can from this ES-kape as you all well know, but I feel like I've been chasing my tail since no matter what I do I have not been able to retain RPM once the engine gets hot. Water cooled muffler helped a little, cold air intake did too, but nothing like my 2003 or 2011 boats. So I started thinking outside the box and realized the air coming INTO the "box" was coming in through a smaller volume shroud, so I held the two up for comparison and sure enough the ES-kape shroud is only 2/3rds the size of the previous models shroud. These engines NEED lots of air, as much as that flywheel can suck in. Restricting that flow has got to be causing the heat issues, so I went to town chopping up the shroud and making it deeper. Opened up the hood and made a new scoop to accommodate as well. Will have more pictures and test results Saturday.  \./8

I've often wondered how the Honda flywheel intake volume capacity compares to the Robin Subaru flywheel intake volume since mine is a Honda to Robin conversion. I believe you have each, how do they compare Tom?

I've not had any cooling issues with my 2003, it will hold it's RPM all day like my 2011, so I would be willing to bet it is comparable to the Subaru. I'll get some pictures later today for comparison sake.


Old hull plenum is comparable in size, yet not as tall, so air has a more direct path into the flywheel. The two old models provided suitable cooling ability, the Subaru models needed to have the hood opened up though so the inlet was the same size as the tunnel.

Larger plenum worked like a charm. Zero heat issues today, motor ran beautifully. Now I know that all the performance loss issues I've had with all of these ES-kapes is related to overheating. Air cooled motors need lots of air and the stock plenum chokes that down to a fraction of what is needed for sustained running. I always wondered why they made that inlet so tiny, I guess they skipped the testing part since it looked cool.  :D



That's interesting,  is there any way to modify the stock plenum on the es-kape without too much chopping  and altering to attain  that extra air flow, or is it a total redo? Would adding a flared scoop to the outside be enough or is it the necking down that's causing the air restriction?


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