2nd Start Solenoid on negative.

[noelex 77]

Originally Posted by xslim

Woud a big relay work for negative?
Anyone have ideas how much amps is going thru the starter?

Ideally you want a high capacity relay, but I have found suprisingly small relays rated at only 80-100A continuous seem quite durable in this application. I suspect that the short duration of the starting current gives the contacts little chance to heat up.

The relays can fail in the closed position so make sure you have an indicator for this fault.

[boatpoker]

Originally Posted by DougR

Today saildrives are electrically isolated from the engine with nonconducting gaskets and washers. It achieves the same goals without the electrical complexity.

Only Volvo drives are isolated. Yanmar's are bonded.

[noelex 77]

Originally Posted by funjohnson

Based on a lot of internet hunting, I found VDO double pole senders in Europe. I'm able to get these for around $400 shipped to the US. Unfortunately, the money isn't in the bank, so we'll just rely on using a Bluesea 6010 switch to connect the ground to the engine block when we're using the engine. I hope that semi-short use won't cause corrosion issues down the road.

Matt

Normally single pole oil pressure and temperature alarms are only grounded in their alarm state. So these can be left connected. When the engine is running (with normal/high oil pressure and normal/low temperature) they will not ground the engine block.

So an alternative to dual pole senders is to rely on the alarms and wire the temperature and oil pressure gauges to a momentary switch. While this is not ideal I feel it is preferable to grounding the hull while the engine is running. The momentary switch alows the guages to be read but the alarms are working permantly.

[xslim]

Originally Posted by noelex 77

Ideally you want a high capacity relay, but I have found suprisingly small relays rated at only 80-100A continuous seem quite durable in this application. I suspect that the short duration of the starting current gives the contacts little chance to heat up.

So you had a solution working with 100A relay?
What engine you had and how long you had a solution?

About double pole senders - there are a lot of them for Perkins on this site - Parts4Engines for Perkins & Volvo Penta Engine Parts

I guess some might be compatible to other engines.

[noelex 77]

Originally Posted by xslim

So you had a solution working with 100A relay?
What engine you had and how long you had a solution?

The relay was on a 62hp 5 cylinder Nanni. I changed it, as a precaution, with a larger relay after about a year, it had been fitted to the engine several years before.