Where to put temp sender

[tmcalavy]

Installed most of my Faria temp gauge kit last nite, but can't find a good place to put the sender on my mid-70's Merc 500 4cyl. 50 hp with Thunderbolt ignition. Instructions say to put it under head bolt, but I know I'll break the head off trying to get one out of an engine this old. Don't want to do that. Anyway, looking at my head, looks like the sender will only fit against the raised fins on the head even if I get a head bolt out intact. Where's the best spot to put a sender on this engine, and how do you attach it if you don't bolt it down?

 

[12Footer]

Re: Where to put temp sender

Senders are not unversally the same in size, shape, or design.<br />Is the one you are using a the type that reads temp from the actual water,like a meat temp gauge?<br />Ot does it clamp onto the outside of the block,to read temp like your hand would laying on a car hood?

 

[tmcalavy]

Re: Where to put temp sender

It's the type that lies flat against the cylinder head. I found a spot forward of the water jacket that heats up, so i put it there and the gauge registers when I run it with the muffs on. Question now is, how warm should the head on these engines get at running speed. I ran it for about 10 minutes with the muffs on and it went about halfway between 60 and 100 degrees. Boat guy says it should run around 140 degrees, but I'm skeptical. Any ideas on normal operating temp for an old Merc 500 50 hp?

 

[Boatist]

Re: Where to put temp sender

Tim<br />Your engine guy is right. Most thermostats open at 145 or 150 degrees and motor runs up to about 170 wide open. Car are usually around 180 to 192 degrees and boats run better at that temp also but in salt water get too many deposits so that is why thay run cooler.