[Putershark]

Originally Posted by 190bayguy

Puter

that was a very good write up and I do agree/understand what your saying.


One thing that I am still having trouble understanding is how boat engines ever get hot enough to run at an efficient heat level. (reaching almost complete combustion)

I will reference again autos: I know that people think they can take the thermostat out and their car "runs better." As some of us better educated individuals know this is NOT the case.

So my question: Are boat engines simply designed to carry less heat away from the jackets because they are running cooler (intake temp) water through the engine. ?

tight lines

Nate

Thanks Nate!
Now I would not say they are "designed" to take away less heat, it is just nature of the beast by the constant strain or "load" on these engines, that they can and will build up heat much faster in the cylinder heads which causes the pre-ignition / knock to occur. Much, much, faster than in your standard passenger car / light truck applications. Matter of fact, I do not of many engines that work as hard and on such a constant basis (maybe light aircraft and some farm tractors) as boat engines are asked to do day in and day out.

Now when you combine that effect with how Honda for example, uses their "lean burn" feedback system to save on fuel burn in the cruise RPM range (by leaning out the fuel mixture even more) it is not hard to see how these combustion chamber temps can soar very fast. So much so, that Honda has built their engines in this HP range to have 3 way cooling systems to combat such. More such information on those systems can be found here

http://www.honda-marine.com/modelDetail.aspx?modelGroup=BF150#

So it becomes clear after a while of tracking (no matter what octane level it "can" run on) how running such high tech engines can show a measured decrease in fuel burn while returning better performance on higher octane fuels. Even more so for me pretty much year round, this since it stays warmer (or down right blazing hot) in this area.

Here again as I have always stated... You need to test and track to know for sure how your hull, engine, and prop combo will perform to give you the best ROI on your fuel purchases in your area

Stay safe and remember, work is just something we all do inbetween fishing trips!
Dave