Hot 4 Stroke Exhaust

[Texasmark]

This is about props, but primarily the engine exhaust that props have to deal with so it's here.

Was reading yesterday about 4 stroke exhaust being hotter than comparable 2 stroke and this is the reason for going away from rubber hubs to plastic.

Is the exhaust hotter and if so, why? Both have cooling water in their exhaust don't they? Run off the same water pump?

Is rubber hub failure a big deal with 4 strokes? I thought the plastic design was to prevent hub slippage with the higher hp engines that rubber apparently has.

Comments appreciated.

Lotta folks buying 4 strokes today. Things like this and making oil or not surely are of interest to them.

Thanks,

Mark

 

[Rancherlee]

Re: Hot 4 Stroke Exhaust

I would have to say yes due to the fact that 4 strokes are more effecent than old carbed 2 strokes. Rich mixtures burn cooler and we all know how much fuel goes out the exhaust on a carbed 2 stroke (which also aids in cooling). DFI 2 strokes also have alot of heat coming out of the exhaust due to the complete combustion and also being clean burning. The leaner the mixture the hotter the exhaust and when you get too lean you know what happens, melted pistons from excessive heat.

 

[JRJ]

Re: Hot 4 Stroke Exhaust

I've run both on muffs, and if anything, my 4stroke has cooler exhaust than my 2stroke did.

 

[tommays]

Re: Hot 4 Stroke Exhaust

No motor runs hot on the muffs ?

When you load the motor under use all the waste heat has to pass through that small area of the prop hub

The fuel NOW is crap and the motors are leaned out to the raged edge to make there 2 or 3 star EPA rateing

No more of those nice brow sparkplugs

And when you running there is really not all that much water and what is comeing out is going to be forced away from the hub buy the g-force of the spining prop


Tommays

 

[Texasmark]

Re: Hot 4 Stroke Exhaust

Well, I'll agree, even on muffs, there isn't a low of water coming out. You'd have thought that you would have enough heat sinking by the propshaft, gearbox, and outer hub via the interconnecting ribs to keep the hub cool enough to keep from burning rubber. I'd think plastic would melt before rubber would.

On brown plugs, Silvertip put me onto some regular gapped NGK plugs that run tan in my 90 hp 3 cyl. Merc.

Mark

 

[jeeperman]

Re: Hot 4 Stroke Exhaust

The leaner the mixture the hotter the exhaust and when you get too lean you know what happens, melted pistons from excessive heat.

And if your timing is off (retarded?) you will gets higher exhaust temps also.