Low Voltage Problem Help???

[Beastb15]

Ok, this might be a lengthy explanation so bear with me. My friend has an '07 X45 and this weekend we had problems continually.

Battery Setup:
This spring I installed new amps, tower speakers, sub and batteries in his boat. He has the standard Blue Sea Battery switch (with Off, 1 Battery and Combine). He also has a VSR to separate the battery banks upon rest.

Problem:
We kept getting a check engine "fault" so-to-speak. After the boat had been sitting a while, we would go to start the boat and it would start up just fine. However, it would go into its "safe mode" (for lack of better terminology) where the engine won't rev, it will only idle.

Solution:
The first solution we came up with was to charge the starting battery. Well, I put my charger on the starting battery. My charger was showing that the battery seemed to be good (showing 12.6 volts at rest, 13.5 volts + with the boat running). My charger also showed that the stereo bank of batteries was 95% charged with a resting voltage of around 13.2 volts. So, I went ahead a threw the charger on and gave it a 30 amp charge for a few minutes. Viola, the boat runs.

Problem:
So after we got the boat running we took off out onto the water (we assumed the alternator would do the rest). The boat would randomly lose power and go back into "safe mode". We could usually restart the boat and it would be fine. After a while, this got annoying.

Solution:
We tried switching starting batteries. We pulled a starting battery out of the other boat (showed 93% charged with a resting voltage of 12.7), charged it up and went on our way. I also checked the alternator output on my battery charger (it was putting out nearly 80%, and varied by the engine revs, so it appeared ok).

Problem:
After we switched batteries, we went to party cove, coved out a few hours, went to a friends, parked it for the night. The next morning as we were leaving, we get a few hundred yards from the dock and bam, the same problem. The boat goes into safe mode. Except this time, restarting it doesn't help (it starts just fine BTW).

Solution:
So we are stuck out on the water looking at an 11 mile ride back home with an idle speed of 5mph. We play with the switches, looking for anything. I decide to combine the batteries in hopes that the large AGM battery bank might *charge* the starting battery. After about 10 minutes of idling, what do you know? It starts running again.

Problem:
But wait, after about 3/4th of a mile, the boat loses power again and goes into safe mode. Tried combining the batteries a few more times and we finally got back home. It appeared to die more often than not when the boat rev'd over 2500 RPM.


Now, what in the world could be wrong with this thing? It *appears* to be a voltage problem (except it never really reads "volt" on the dash, it reads "Check Engine"). Is there a sensor that could be going bad?

Now, here is what I don't THINK it is (but I've been wrong before). I don't think its a bad starting battery (we traded them out, both checked out ok according to my battery charger). I don't think AGM batteries are draining the starting battery (they showed to be nearly fully charged).

Synopsis of the Problem:
- Boat loses power and won't rev
- Charging the starting battery gets it going again
- Traded out the starting battery, gets the same problem
- Boat will lose power even when the alternator is charging the batteries


HELP

[willyt]

it doesnt sound like a voltage problem to me... sounds like an actual check engine code.

whats temp and oil pressure? if its only reving to 2500 rpms might be your TPS sensor. best thing you could do is pull the codes and you can stop guessing.

[Beastb15]

Originally Posted by willyt

it doesnt sound like a voltage problem to me... sounds like an actual check engine code.

whats temp and oil pressure? if its only reving to 2500 rpms might be your TPS sensor. best thing you could do is pull the codes and you can stop guessing.

Well according to the gauges, the temp and oil pressure are smack dab in the middle. I should clarify, it will rev past 2500 rmp, its just that when we actually get the boat to run it tends not to lose power when its around 2k rpm.

What is the TPS sensor? Is there a way to pull the codes without taking it to a mastercraft shop?

Sorry for my ignorance, it's not my boat. It's my friends.