[Vasco]

Common problem with wiring in older boats. Simplest solution is to install a relay. I finally bit the bullet and did that with my 26 year old boat. And I had new batteries! Get a relay from NAPA. Half hour job and the engine will start every time you push the button.

 

[Vasco]

Rick,

I'm not sure I understand? Is this to address an engine control panel switch issue? In my boat, the engine control panel is about 12 to 15 years old, but all other wring is new?

It's for the engine control panel wiring. Installing a relay between the panel wiring and the solenoid will boost the voltage and it'll start every time you push the button. Here's the instructions that I borrowed from another site. Cleaning all the contacts from the control panel might help but installing a relay really works well.

The relay part# I use:
Tyco
12V
V23234-A0001-X032

There are 5 pins on the relay:

87 - Jumper to starter male spade terminal
86 - Wire from Yanmar panel (used to go directly to starter)
30 - Positive jumper from large positive cable attached to starter.
85 - To Ground
87a - Not used

So, without this relay, you have 1 large nut on your starter, with a rather thick positive cable on it (this should come from your start battery). And, you should have 1 smaller cable, with a spade female disconnect on it that is connected to a spade post on the starter (this will come from the Yanmar engine panel at your helm station).

You need to remove this wire from the spade on the starter, connect it to position 86 on the relay. Then you make two short runs of cable, one going back to that spade male terminal on the starter from position 87, and another one from the big nut/positive cable on the starter to position 30 on the relay. Then a short ground wire to your engine ground from position 85 on the relay.

 

[Vasco]

I disagree. The starter solenoid doesn't use much current. That is why there is a solenoid there to start with. If the voltage at the solenoid isn't as high as it should be there is a wiring problem to or from the panel, either gauge, connections corroded, or age of wire. Adding a relay (really another solenoid) will not solve the problem only mask it and add more connections at the same time.

Now if there are glow plugs and they are powered off the panel a relay does make sense as they do use a lot of current.

I agree the problem is from old wiring. But rather than change out the wiring harness it's much easier to install a relay. The relay does not mask the problem it fixes it without having to get a new harness. As I said in an earlier post you might try cleaning all the contacts first.

As for the relay in some newer Yanmar installations a relay is already installed.