New Gauges in an old boat

[IPtraffik]

I received some gauges for free that are brand new. I would like to put these in an old Larson I am almost finished restoring. The new gauges and switches all have a lot more wires coming out of the back than the old ones. Furthermore they have these large square block plugs.

What are the chances I can make these work with an old Mercruiser MCM190 - is there a wiring harness adapter or something? Would there be a large block that all these smaller square plugs go into that I need to buy? Or would this be a case of cutting away the square blocks and joining wires together?

Any help is greatly appreciated.

Thanks!

 

[Struc]

Re: New Gauges in an old boat

I can't give you all the answers, but I can tell you what I learned from working on mine recently.

Have any pictures you can post? Do you know what year boat your new gauges came from? If you can find that out, then you can look up the wiring diagram in the service manual for that year. The large connector plugs - does one have larger connectors and 10 pins (9 wires though, I believe)? If so, that's the same as I have, and that is for the ignition switch and gauges. The other one is for the accessories (switch panel / toggle switches).

Assuming it's the same as mine at the gauges, purple is 12v+ and black is 12V-. You'll probably have an extra 2 wires going to each gauge for backlighting. Tan going to Water Temp, Light Blue going to oil pressure, Grey for the tach, and Brown/White for the trim gauge. Sound right?

First thing to confirm is that the sensor range on your sensors is the same as what the gauges will expect, or you'll end up swapping out the sensors. Also, does the tach have a switch on the back for the correct number of cylinders? Once you know they will work (pretty likely), then you'll have to decide if you want to buy a whole wiring harness to plug in, to replace the one you have, or simply splice it in.

 

[IPtraffik]

Re: New Gauges in an old boat

Attached are some pictures of the gauges , switches and ignition.

The set of gauges looks to be labeled as follows - CRSTLNR K07 SPTFSH IO MERC 3PC - Crestliner Sport/Fish ?

The ignition plug has a 10 pin (actually 9 / with 9 wires)

The switches plug has a 10 pin (actually 6 / with 6 wires) and a large 15 pin plug with 15 pins wires

The gauges have 3 10 pin plugs ( actually 9 / with 9 wires)



How do I confirm the sensors are the same? Yes the tach allows me to select the correct number of cylinders - position 1 = 4 cylinders. I would prefer to buy a harness and/or adapter - I just have no idea which is the right one - the old one was pretty much shot, I saved it but would prefer not to use it.

 

[Struc]

Re: New Gauges in an old boat

Based on your pictures, I'm not going to be much help.

Looks like those are much newer. The bright side is that you show it labeled as Merc, so I'm sure there is a wiring diagram in one of the service manuals out there. You just have to figure out which one. I'll eliminate #7.

 

[Silvertip]

Re: New Gauges in an old boat

Outboard tachs are not dependent on the number of cylinders an engine has. A 40 HP engine with 12 pole alternator is set the same as for an a V6 with a 12 pole altnerator. Both of those would be set to 6P. The tach reads pulses from the charging system stator, not the engine ignition system. If you have an I/O then the tach reads ignition pulses and you would need to make the proper # of cylinders selection. Fuel gauge senders are 30 ohms full tank, 240 ohms empty tank and 109 ohms (roughly) for 1/2 tank. Trim gauges and senders must match the engine. There is no sender for a speedo but a pitot is required. This may be a separate unit mounted at the stern, or the lower unit may have one built-in. Voltmeters need no sender.