Reply To: Backfire/misfire thru carb

[Don]

OK, agreed that the thermostat set up is terrible…You can’t get at the bolts on the conventional outboards, not to mention having them rusted in place…Then trying to get all those pieces/parts/springs/gaskets back installed properly is usually an exercise in frustration….
There is much more room under the top of the head for those elbows, and it is at the top of the water flow circuit, so this greatly reduces the chance that air will get trapped in the system…If you are going to do anything, I would probably just install the original black turbo jet heads/elbows back on the 140hp powerhead. When you have the heads off, compare the combustion chambers and you will see that the turbo jet heads have much less “squish” resulting in lower compression/longer engine life. There isn’t much meat on the cylinder head water cover for threads, and very little room behind the cover as well. Again, the nature of this jet system is prone to taking in alot of air while bouncing around, so I feel the elbows would constantly be purging air, not just when first started. Be sure to replace the head gaskets if you decide to make this swap.
As far as the fellow who is emailing you, I’m certainly not saying he is “wrong”. But, obviously the powerhead swap works. The trick will be longevity….These things are subject to harsh use, so they are more likely to have overheat/detonation/preignition issues. Get it buttoned up, and sell it off….