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Old 07-17-2013, 12:51 AM   #1
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Default Gauge/Wiring Diagram Question 1996 Maxum 2300SR

Hi All,

I am a new boat owner '96 Maxum 2300SR with Merc Cruiser 7.4l, Bravo 3, however I have been using the boat I bought for the last 8 years. I purchased the boat from a friend who did little to no maintenance unless something broke but of course nothing did when he had it. I started the year out with great intentions and had a mechanic go through it prior to hitting the water but it has still been one thing after another.

I put the boat in a valet service in NH. The valet slip was supposed to be inside and covered. When I dropped the boat off it needed a new impeller pump. I had been on the boat when it started heating up so I pulled it out and trailered it to the marina. I left the boat uncovered because they were going to try and work on it that day, of course they didn't. Once they fixed the impeller they put the boat in an outside rack uncovered where it got rained on for two weeks. When I got the boat this weekend the glove box had about 2" of water in it.

While I was out on the water this weekend I tried using the cigarette lighter to power an air pump. After only a few seconds the pump died. I was able to plug my cell phone charger in and it appeared to be working so I assumed the pump to be broken. Shortly after this while underway I notiIced all of my gauges, (water temp, oil pressure, fuel) were all pinned to the right. I was able to check the manifolds and determine the cooling system appeared to be working and was able to motor to shore without a problem. Now that I think of it, I believe the volt gauge was showing normal, between 12-14v while the engine was running. I think the trim gauge may have been working correctly too but I am not positive of that at this point.

Has anyone seen any type of a similar problem, maybe due to water or a short?

Does anyone know where I can find any time of wiring diagram of how those gauges are wired?

Any input or advice would be appreciated!
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Old 07-17-2013, 02:45 AM   #2
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Since it affects all the gages, I would start looking for a ground problem with the alternator or battery. If the gages are all pegged high, it sounds like the electrical system is trying to use the smaller grounds to complete the circuit since a larger one that would normally carry the load has high resistance. Look for big black cables and where they attach for corrosion or rust problems. I'm a mechanical engineer and not an electrical one, so maybe a more experienced member will join in. By the way, where in NH are you?

-JP
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Old 07-17-2013, 01:16 PM   #3
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Welcome aboarde mreardon!!!
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Old 07-17-2013, 04:27 PM   #4
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mreardon, first welcome.

1. Impeller replacement is part of standard maintance ~ every 2 years.
2. Boats are designed to get wet, but left uncovered for long periods of time will lead to premature failure of seats, wiring, ... If you had the boat uncovered most mechanics will not install the cover, hoever if it was covered that should have re-installed it.

3. All guages pegged high. I had this happen on a truck I once owned, it was from a failed regulator but the volt meter was also high. I am assuming the spedo is not pegged as the only electrical thing in it is the light. Here is a wiring diagram of the helm.

Helm wiring.pdf
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Old 07-23-2013, 01:34 PM   #5
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So I got back to the boat yesterday. We found the ground wire coming from the engine compartment to the fuse block was showing a small amount of resistance. The connections under the dash all appeared ok. It appeared the ground wire went from the battery terminal to somewhere behind the engine then to the fuse block under the dash. Since we weren't able to get behind the engine to completely try and trace out the bad wire we put a second ground wire from the fuse block back to the battery. Would loved to have traced out the bad wire and tried to find the source of the problem but getting behnd/ below the engine is not an easy task for humans this will have to do. Problem solved! Thanks to all for the help!!
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Old 07-23-2013, 04:10 PM   #6
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To help you see behind the engine get a mechanics mirror (small mirror on a extendable arm). Mostlikely goes to bolt on back engine or a ground block mounted on the inner transom.

Question ground on the fuse block? usually fuse blocks are only dealing with hot wires. Any pictures?
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Old 07-23-2013, 04:28 PM   #7
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I don't have pictures, ill try next week when I'm back.

There was definitely a ground post under the dash where everything was grounded to. That block had a wire running back to the engine which we could see eventually got to the battery post but we lost sight of it as it went behind the engine, so we couldn't see all of the connections. It's possible it ran straight back to the battery but we couldn't positively trace it back.

When we put a meter on the ground wire under the dash we measured a small amount of resistance, approximately 1 ohm in the wire. When we put a jumper from the ground post under the dash directly to the battery ground all of the gauges worked properly. That lead us to believe there were additional connections in the ground wire somewhere behind the engine which were causing the problem.

The funny thing was when I got to the boat and started it all the gauges were working fine. While I warmed it up at the dock they seemed to be fine. Once I plugged an air pump into the cigarette plug and ran it for about 20 secs the gauges failed. No amount of rest, having the ignition off or batteries off would reset the gauges, only the new ground.
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Old 07-23-2013, 09:59 PM   #8
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Sounds like the air pump pulled more current than the ground could handle returning. Did you disconnect the old ground at both ends when running the new ground? The old one may have damaged insulation causing a ground loop if shorted to metal (but with resistance i.e. not a hard short).
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Old 07-23-2013, 10:04 PM   #9
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No we didn't disconnect the old one. We thought of it but because we couldn't tell what else it was connected to we were concerned having other Equiptment not grounded. Everything seemed to run/work fine but that was definitely a concern.
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