Starboard EGTs 600 deg when trying to accelerate

[Moonshot180]

Merc 260. Re-ring 3 years ago, approx 45 hrs on re-ring.

Already replaced, stator, trigger, battery, ECU.

Installed a Brucato ACU and that fixed it, or so I thought.


As long as I am crusing, low speeds, EGTs are the same, and motor sounds like all six are firing.

When I accelerate, and/or try to run high speeds, the Starboard EGTs drop to around 5-600 degrees, at the same time, the Port side EGTs jump to around 1000 deg, depending on where I place the steam wheel.

Not sure what else would be causing this issue. I would love to try out another ECU, just to rule out a failed program. I am open to other ideas also.

Thanks in advance Scream and Fly!

[StratosVT]

Does the boat run ok and sound ok? Do the plugs look ok? If yes, you probably just have a bad egt probe or its at a different depth than the port side. If no, you may have a bad switch box.

[Moonshot180]

thanks for the help StratosVT, boat runs and sounds good when crusing at low speeds, low rpms. Boat idles great, just when you are really in the throttle is when you can feel the power loss and it doesn't sound good..

[97 TWISTER]

When was the last time injectors cleaned and flow tested??? Like mentioned above it should be easy to see if it is a "to much fuel" issue by checking plugs and pistons. Have you done compression test recently??? Just where I start would looking. Good Luck

[Dave Strong]

Start by swaping the probes and see if the issue follows the probe.

Dave

[StratosVT]

thanks for the help StratosVT, boat runs and sounds good when crusing at low speeds, low rpms. Boat idles great, just when you are really in the throttle is when you can feel the power loss and it doesn't sound good..

Pull the plugs and check for damage. Do a compression check also. If the whole bank of cylinders is running bad its likely a switchbox but if it's just one hole more stuff comes into play. Whatever you do DON'T run it until you find the problem. Whatever part it is will be cheaper than fixing a blown up motor. Ask me how I know this

[Moonshot180]

I had pulled the probes and swapped them and it isn't a probe issue. I also pulled the heads off and inspected the cylinders/pistons and they looked good. I haven't done a compression check though, and I haven't paid much attention to the o-ring seals either (maybe I should have).

I replaced switchboxes before, and did not see a change, would it be possible that I different set of switchboxes could be bad? I would be open to try some more..

During accelerations and high speed attempts, I will adjust the fuel curve on the steam wheel to lean it out...Port side responds like it should and temps rise above 1K deg, starboard still just loafs around 5-600 deg..

Its been over 3 yrs since I have had the injectors flowed..maybe they are due?

[Moonshot180]

hey just thought of something...could I swap the switch boxes I have already? See if the problem I am seeing swaps from starboard to port?

[StratosVT]

hey just thought of something...could I swap the switch boxes I have already? See if the problem I am seeing swaps from starboard to port?

You could but I'd be afraid of blowing it up if you keep running it. New switchboxes can sometimes be bad so yes it'd be worth it to try some different ones if you can. Based on the egt reading we're assuming it's the entire bank but it could be just one hole causing the problem. For example if a coil isn't firing, the egt on that bank would definitely be cooler. Before changing boxes, maybe run it on the hose and check coils to make sure they're all firing and none are arcing (look for spark shooting from coil to block).

[Moonshot180]

I wonder if a bad coil/s arcing to the block would take out an ECU? This whole thing started by me going to the lake, putting in and motor would not hit, fire, nothing...found out the factory ECU was fried. Was not even able to have it re-programmed. Bought a replacement from Brucato, great ACU btw (ran over 100 with it several times) ..but after a short while, that ACU went bad, and Tony was able to re-program it. Before I ran the engine again, I replaced, stator, switch boxes, trigger, battery. After replacing all that stuff, I have been left with the situation I have now, where the motor runs with EGT readings showing starboard firing problems..

I have yet to replace any coils...