Mercruiser 454 temp help

[fastimz]

I have a gen IV 454 Mercruiser which is carbed, and turning a Bravo iii. I replaced the temp sending unit the other day but I ordered the wrong thread. The manifold has 1/2 npt and the sender was 3/8 npt. I used a brass bushing to use it. I took the boat out for the first time this season and the engine ran great. The temp gauge stayed on 175 the entire time I was out. Never higher, never lower. I can't remember to save my life what it ran last season. Could the sending unit be causing the problem, thermostat? Any ideas? Thanks

 

[Don S]

Re: Mercruiser 454 temp help

175 sounds about right to me, what's the problem?

 

[fastimz]

Re: Mercruiser 454 temp help

I thought that it ran that before because that puts the needle over the 175 number. I just wanted to make sure because everyone started telling me a raw water system should be cooler, blah blah blah. I ran perfect but I couldn't remember what it should be at to save my life. Should I have a 140 thermostat since I run a raw water system? Mostly salt or brakish water? Thanks for the reply.

 

[tpenfield]

Re: Mercruiser 454 temp help

My Merc 454 Mark IV ran 155 F all day long. It could be differences in the guage/sender. However . . . for you, if it was same as before, then no worries.

 

[Don S]

Re: Mercruiser 454 temp help

Get an IR temp gun and check the engine and find out for sure what it is.

 

[MarkSee]

Re: Mercruiser 454 temp help

Like Don indicated, find a different way to check.

I have a 2000 7.4 which I think might be called a gen VI(?) and is a mpi rwc unit which are known to run a little warmer and my gauge would show a little over the 175 mark.

When my mobile mechanic had it on a scan tool running around in the Pacific, he was finding readings steady between 169-170 on the tool.

So I just figured the scan tool is correct and the gauge reads a little high so as long as it stays just a little over the 175 mark, I'm good to keep on going.

Mark

 

[Speakrdude]

Re: Mercruiser 454 temp help

Make sure you ordered the right sender for a single (or dual) console. The wrong sender will read 20 degrees higher.