Kanookstr

I did the very same thing!!!! I am glad i did it, because I wouldn't of believed it if I hadn't seen it for myself.
in my 1999 502 mag MPI fully stock with stock Merc exhaust. I seen 1500°+ at wot I couldn't believe it!!!! I then installed my procharger at 6 psi boost and it ran 1350°-1400°
WTF cooler with the procharger???(it does have an inter cooler though) then the next season I installed Gil manifolds, and my EGT's dropped to 1275°-1300°.

By a new boat in 2002, same 502 mag MPI, installed an egt gauge because I planed on putting a procharger on this engine as well. ran it for one season stock. Sure enough, this 502 mag MPI stock read EGT's over 1500° at wot . I ran it the whole season that way. i figured one engine could be a fluke, but two of them 3 years apart??? well it ran fine all season with no problems (wasn't scared, it was under warranty) So for piece of mind, I would install your EGT gauge before your mods. you'll be shocked..

cooltoys61

Ok,,How about what's too low? Is there a # or is it like the high end ,depends,depends???

MESABALANCING

COOLTOY
IF YOU WOULD LIKE TO GIVE ME A CALL I WILL TELL YOU SOMETHING I HAVE FOUND WITH THIS PROBLEM YOUR HAVING AND I CAN EXPLAIN WHATS HAPPENING AND PERHAPS HOW TO FIX IT.LAZ MESA WWW.MESABALANCING.COM

Kanookstr

Well too low you'd be to rich. An air/fuel meter is the best way to be perfect. But a good one thats very accurate is expensive, let alone having to make an adapter to hold the o2 sensor without it getting into contact with water from the exhaust. EGT's at around 1250°-1300° would be a good range to calibrate to. then you should read a plug to be sure. On a carb motor, I use to jet till the EGT's didn't change, then down one jet size. But to much fuel can also cause high EGT's. theres a fine line there.
I had a twin turbo motor that I couldn't get the EGT's down. I kept going up and up in jets, but the temps stayed high and never went down. I finally tried going the other way, and after a while I finally seen the temps start going down. what was happening was, the extra fuel was burning in the manifolds and that was making the EGT's high.

cooltoys61

Thank you, I think I have my answer(s).I'm gonna check it before boost and expect around 1300 to1500 and after boosting try to keep it under 1300. I have been told by a couple of knowledgable folks 1325 is pushing it and honestly at this point and this time of year I want to get it back in the water and help it stay together so I will prob give up a lot of HP and gas until late,late fall then try to get it crisp without getting it crispy. I just bought the boat('90 Fountain '29 w/454Mags) and tore it apart when it was running fine just because I saw a deal on 2 M#'s on EBAY. Now I'm almost ready to just run it with the belts off,,ALMOST. The hard part was assembling all the pumps,filters,lines,regs,return lines,crossovers,etc because each change mandated another(that's hotrodding).I've built a few engs and a few boats,Cobra kit,car etc but never anything SC'd. This board has been a great help.Thanks,Allen

HPJunkie

My motor runs 1325 to 1375 on the #2 and #7 cylinders at the ports. the plugs NGK5671-8 always look black, but the transom is not sooted up. I have an M-1 procharger at 9# at 6000 rpm. 1375 seemed high to me also but no failure cylinders look like new. I wouldnt mind trying to lean it out a bit for some more top end, .. but its working OK right now and Im on the 2nd season. My carb has 84f/98r and a 4.5 power valve in front and the reaar plugged. Procharger recommends the 750 holley for a stronger signal. I am pleased how my system runs. Greg

cooltoys61

WOW,that's the best info I've had after many tries. Thanks. That's a sharp boat,Nordic? I had a 22 Nordic Jet and love the way they design and build. Give me more,,timing,fuel,base motor,changes.6000 is humming,I wouldn't be afraid to run a 454 mag that hard but what boost do you have at 5000 or so?Is there a big change in boost at the top? What pulley is that that gives you 9 at 6k?Sorry for all the Q's and thanks for any answers

mcollinstn

Also matters where you take your reading.
Bottom line is that you must do plug readings to get your mix right. Then gotta watch the heat line to get the plug heat range right. Then gotta tweak your timing for low end of best power. When you have everything right, then you note what your EGT's are on your motor.

Once you establish a baseline, you use them to watch for something going wrong as much as anything else.

They are a tuning AID but cannot be used alone.

Strip Poker 388

iTrader: (6)

Is the r5671 plug a non projected tip plug . this may be the soot prob. i ran the R5674-8 Projected tip in my blower motors and had no probs. I also run them in My chevelle on the NOS and the 9's the 8's are too cold for the street.The Scarab blower motor on the dyno never got over 1375 , it was on a safe set up.The last time I dynoed we where trying to tune it at mid range cruz rpm 3000-3600. pulled it up to 3600 and pulled it down with the dyno break to simulate the boat and keep the rpm constant ,adjusted the secondary circuit to make sure it was it was rich enough . the longer you held it with this kind of load on which was more that the boat the higher the temps went up.


Pump gas usually runs a higher egt temps. I called the techs at Merc racing in Florida and asked them . they said they would run the 500 efi's up to 1500 on the dyno with no problems. Mine runs that high and I don't see any speckling on the plugs mr43t's.I did notice when I put the gas treatment in it would go higher1575 still no speckling on the plugs.

On the Race cars on the nos motors the egt's never got to high even when it detonated .

At 31 dr on timing .I have seen low timing have high temps also.

cooltoys61

I'm starting to get it,thanks and keep it coming. My pyro says don't shorten the wires as obviously it will change the resistance so I guess if I lengthen I need to get a reading before and compensate after. I know there's a formula but I wouldn't trust it anyway without testing. If I use really heavy wires it should help,right?