Thread:

Help a boater diagnose a 496 Mag issue....

496 Mag Issue


Looking for some opinions on what might be wrong with the 496 Mag in our boat.

On our very last trip out last season the engine developed an issue where it would start but have limited power when it was cold. Once it reached normal operating temp (160) it would run fine. The engine almost behaved like it was flooded. Even with full throttle it didn't have enough power to even get on plane, until it came up to operating temp.

So I had it in for service over the winter. The repair shop checked the plugs, alternator voltage, and replaced the fuel filter. No codes were set or pending. According to them it ran fine on the hose. About a month later we attempted to use the boat and once again it did the exact same thing, except this time the problem did not go away after the engine came up to normal operating temp. I could smell strong gas fumes and the boat barely made it back to the trailer. This issue has definitely gotten worse.

Any suggestions?

http://www.performanceboats.com//showthread.php?t=37171


Thanks.

Originally Posted by Cole Trickle

496 Mag Issue


Looking for some opinions on what might be wrong with the 496 Mag in our boat.

On our very last trip out last season the engine developed an issue where it would start but have limited power when it was cold. Once it reached normal operating temp (160) it would run fine. The engine almost behaved like it was flooded. Even with full throttle it didn't have enough power to even get on plane, until it came up to operating temp.

So I had it in for service over the winter. The repair shop checked the plugs, alternator voltage, and replaced the fuel filter. No codes were set or pending. According to them it ran fine on the hose. About a month later we attempted to use the boat and once again it did the exact same thing, except this time the problem did not go away after the engine came up to normal operating temp. I could smell strong gas fumes and the boat barely made it back to the trailer. This issue has definitely gotten worse.

Any suggestions?

http://www.performanceboats.com//showthread.php?t=37171


Thanks.

Sell it!! JK. I have no clue just thought I'd throw that out. Kinda weird that no codes are popping up. Good Luck!!

Originally Posted by Cole Trickle

496 Mag Issue


Looking for some opinions on what might be wrong with the 496 Mag in our boat.

On our very last trip out last season the engine developed an issue where it would start but have limited power when it was cold. Once it reached normal operating temp (160) it would run fine. The engine almost behaved like it was flooded. Even with full throttle it didn't have enough power to even get on plane, until it came up to operating temp.

So I had it in for service over the winter. The repair shop checked the plugs, alternator voltage, and replaced the fuel filter. No codes were set or pending. According to them it ran fine on the hose. About a month later we attempted to use the boat and once again it did the exact same thing, except this time the problem did not go away after the engine came up to normal operating temp. I could smell strong gas fumes and the boat barely made it back to the trailer. This issue has definitely gotten worse.

Any suggestions?

http://www.performanceboats.com//showthread.php?t=37171


Thanks.

Fuel pressure regulator ???

sounds like a fuel issue to me as well...regulator, injector etc

You may want to check out you fuel lines. I had a friend with a similar issue and the fuel lines were deteriorating and collapsing. Reduce flow.

Fuel lines or filter or fuel water seperator..........

What model is the motor? Have you put a pressure guage on the fuel rail to check it? Will it clean out in neutral? and last but not least do you have a scan tool or access to one? It could possibly be that the temp sensor is bad but without a scan tool you are shooting in the dark. The guage uses a different sender than the computer.

Originally Posted by PLACECRAFT20

What model is the motor? Have you put a pressure guage on the fuel rail to check it? Will it clean out in neutral? and last but not least do you have a scan tool or access to one? It could possibly be that the temp sensor is bad but without a scan tool you are shooting in the dark. The guage uses a different sender than the computer.

03 Merc 496 Mag

Originally Posted by Cole Trickle

496 Mag Issue


Looking for some opinions on what might be wrong with the 496 Mag in our boat.

On our very last trip out last season the engine developed an issue where it would start but have limited power when it was cold. Once it reached normal operating temp (160) it would run fine. The engine almost behaved like it was flooded. Even with full throttle it didn't have enough power to even get on plane, until it came up to operating temp.

So I had it in for service over the winter. The repair shop checked the plugs, alternator voltage, and replaced the fuel filter. No codes were set or pending. According to them it ran fine on the hose. About a month later we attempted to use the boat and once again it did the exact same thing, except this time the problem did not go away after the engine came up to normal operating temp. I could smell strong gas fumes and the boat barely made it back to the trailer. This issue has definitely gotten worse.

Any suggestions?

http://www.performanceboats.com//showthread.php?t=37171


Thanks.

buy my HO..you'll be better off..

Originally Posted by Unforgiven

buy my HO..you'll be better off..

Not my boat I already have a 120 hour HO that dosen't get used in my 05 Sleek.

They have zero desire or need for a new motor

I have the 03 manual at my shop that I will look at tonight. Do you have access to a scan tool?

had the same problem,496 mag took it to one shop in havasu and they replaced the computer $1400.00. told me it ran fine.put it in the water and problem still thier.in the shop three times in one year no luck.
took it over to Alco Marine and they pulled all the injectors out and found two bad and the rest clogged.problem solved. $350.00
needless to say i don't go to my regular shop any more