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pyrometer temp. dropping on left side when accelerating

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my 2004 merc 2.5 exhaust temp. is dropping about 500 deg. when you punch down on throttle and when the boat levels off it comes back up to match the right side exhaust temp. Did anybody ever experience this?

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my 2004 merc 2.5 exhaust temp. is dropping about 500 deg. when you punch down on throttle and when the boat levels off it comes back up to match the right side exhaust temp. Did anybody ever experience this?

Yep, I ran into it. I tried replacing the stator, trigger, swapped coils, looked for water leaks, etc. Never did figure it out. However, I later had the injectors tested from that motor and 4 of the 6 didn't pass. Maybe something to look into.

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my 2004 merc 2.5 exhaust temp. is dropping about 500 deg. when you punch down on throttle and when the boat levels off it comes back up to match the right side exhaust temp. Did anybody ever experience this?

Yep, I ran into it. I tried replacing the stator, trigger, swapped coils, looked for water leaks, etc. Never did figure it out. However, I later had the injectors tested from that motor and 4 of the 6 didn't pass. Maybe something to look into.

Have you removed the head(s) and looked for signs of detonation?

Start by looking at the metal portion of the head gasket for dents or dings. Light detonation

Also look at the pistons and heads for small pock marks. Heavy detonation

The left bank (especially on the center and lowest bores) tends to ping first. If the pinging continues, detonation will set in. Detonation wis erratic combustion that causes small explosions instead of a complete burn in the combustion chamber. As a result, gas temps drop.

I hope this helps.

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