Rookie asks Pyrometer??

[B.Mac]

My vector was a drag boat & came w/ a pyrometer (less motor)I put in a floor & now run a 200 Merc w/6"JP/Cone/LWP/relieved exhaust/solids/dual rack & 28 chopper. What will this instrument tell me (i'm assuming exhaust gas temp) and why is this so critical to have a gauge to monitor this temp?

Thanks.....B.MAC

[Rickracer]

That pyro will help you get your motor jetted properly, and help warn you of any fuel related problems, helping to avoid a piston meltdown. Basically, you wanna stay below 1200* to avoid any troubles. This is probably a bit of an oversimplification. It is definitely a good thing to have though. There are entire threads about this subject, so have a look for them, and you'll learn a lot.

[TTriton]

Its not cridical or even important on a STOCK fishing motor but when you start squezing more HP out of ANY engine you need to know that your not taking the engine to a lean condiditon that will melt pistons and blow your engine. And as mentioned before it does help with tuning the engine. You can just watch the guage and tell where your at rather then pulling the plugs and tring to see where your at by guaging the color of the plugs.

[Dewey]

On a stock 2.5 260 EFI that didn't have a pyrometer or a Fuel pressure guage, which would you install first?

Bill

[Jay Smith]

Dewey,

I would install the fuel pressure gauge first , hands down ! A pryo like sited above is a tuning tool for jetting and fuel curve setting adjustments. However I do not suggest a person get a warm and fuzzy feeling about one being able to "save" a motor when ones gets a piston temp reading with an early signal from a slow indicating pyro gauge. A 10,000 rpm motor with the Mercury stroke lenth has a piston speed of around 120 times a second and if people think they can "save" a piston from gaulding with a gauge that will read an increase to a danger level 1 to 3 seconds later is dreaming. Use them for a tuning tool only and afterwards I remove them from the exhaust as ANY obstruction in the exhaust path WILL cause a slight RPM drop.And like I stated a fuel pressure gauge can give early warning if something is going amiss with the fuel system continously !Any slight drop can be monitured.Pryos are not accurate either they can be even effected by "coking" up of oil on the probes and to the person not versed in tuning the motor can be super rich reading flame instead of EGT's and make a person chase thier tail seeing in some cases temps of 1350 showing lean , which a piston would be a molten glob if this reading was correct!


Jay @ JSRE

Jay @ JSRE

[sosmerc]

Appreciate your thoughts about pyros, Jay. I would imagine that the exact location of the probes is also important regarding what would be considered a "safe" reading. If the probes are going through the two bolts at the bottom of the exhaust cover the reading will be different than if the probes are down lower in the exhaust adapter plate.
Have you ever put any kind of temp probe on (or under) the spark plugs? If so, what are your thoughts about what a safe expected temp would be with a pretty much stock 2.5 200? I have the ability to monitor these temps (haven't hooked it up yet on the particular engine I'm playing with) but I've hooked them up on other motors and the temps rise and fall pretty quickly similar to EGT....and I certainly agree that if the engine is going to go above the danger point the EGT is probably only going to give you a hint as to "what happened"...after the fact!