Overspeed alarm at 4000RPM IN GEAR!

[tmylott]

I have a 270 searay AJ with 350 mags. I put the boat in the water for the first time this season and was running along to get on plane. I got up to about 3700 rpm and my port motor started to backfire a little bit I tried to accelerate more and got to about 4000 rpm and I got an overspeed alarm. I have ran into a similar situation in my old boat where the computer thought I was in neutral so it was thinking I was over reving the motor in neutral. I had my friend come down who has the CDS software and to my surprise the computer says that is the overspeed alarm IN GEAR. no clue why is is throwing this code if the computer thinks I am in gear. The rev limiter isn't even close to 4000 rpm. any input would be greatly appreciated the serial number is OW690216. the boat is an inboard. not to familiar with the transmissions but they sound ok...

 

[alldodge]

You have the PCM-555 and I don't have the 555 manual but there is nothing which shows that one. What it does say for overspeed is check the rev limit. The scanner or software show list what it's set at.

Does your have digital shift?

 

[tmylott]

No dts. And that's what I would check if it was the Rev limiter in neutral. But the computer says that the pcm thinks it's in gear which it is. I don't understand how it can think it's hitting the Rev limiter at 4000 rpm in gear when the Rev limiter in gear is 6300 rpm. I tried swapping pcms with my other motor and it still has the same symptoms on the same motor. It didn't follow the pcm.

 

[alldodge]

It's not the neutral switch because it saying it's in gear, but the rev limit is being hit. Manual 31 list 5.7 MPI mag WOT for ski and inboard is 4400-4800. So I will guess your rev limit is in the 5000 range.

The PCM is getting it's info from the distributer and it could be it. Does your motor have the carb style cap, flat style?

Check the connectors on the distributer

Also check you transmission fluid

 

[Fun Times]

Is your friend with the CDS a Mercruiser tech? There didn't seem to be any other parameters out of range while looking at the live data or fault history reports?

What was the Available Power at % wise? If all was good it starts at 100% and works it way down to 5ish when there's a critical situation.

One thing to bear in mind with this system is that once your available power starts to drop so does the over speed limit system alarm. For example, Say your max RPM is 5000 RPM at 100% power. If the power drops to 94%, the over speed limit drops and if you try to throttle over the new internally programmed limit of say 4800 RPM, the alarm will sound.

0W690216 is an MIE 350 MPI HORIZON 63IV 2.0

 

[Bt Doctur]

Somebody better come up with a way to disable these sensors with resistors.I`m pretty sure I would know if my motor was over reving in gear or out of gear.