The relay on my Lancair IV hydraulic pump became intermittent after a few hundred gear cycles.  Usually worked, but stopped and required recycling of gear handle and some pressure pulses to get it to work again. 

 

A good friend who used to run a marine supply and repair business said that in England where he used to live and here in Australia, only Cole Hersee relays were acceptable to marine authorities for critical ships power systems.  Nothing else qualifies. 

 

Our local auto store sells both the  cheapies and the Cole Hersee (seaport town), both intermittent for starters, and continuous for up to 80 amps.  Removed the intermittent starter-style relay that came with the kit, put in the continuous duty (same external dimensions, configuration) since the circuit breaker on that circuit is 50 amps, had to rewire the relay (intermittent and continuous duty are wired differently - one grounds to case, other does not), and works fine so far. 

 

But they cost.   Out here in  Australia, figure about $80, but all that know their stuff in this area said it is well worth the money, and legally required off-shore.  I note that URL for the relay vendor in one of the email carries Cole Hersee.  Go for it.

 

Fred Moreno