New plugs causing engines to run hotter???

dsiekman

Senior Chief Petty Officer
Joined
Jul 7, 2010
Messages
798
Hey guys, did new risers and manifolds and new circ pumps this year. Checked impellers and both were in good condition - still full vanes and no set. My twins both have always run about 165-168. I replaced the plugs with the factory spec champion plugs which were the same plugs I pulled out. The spec gap is 1.1 mm or .045. The old plugs on the port side were gapped about .035 and the stbd side was about .04. So I installed the new plugs and fired it up. Seems to run great. So, we took her out for the maiden voyage and she ran fine except she was running just shy of 175 both on plane and at idle. Three questions:

1. Is it time for new t-stats? It has been about three years and I boat in brackish water.

2. Is it possible that the plugs gapped correctly are causing the engines to run hotter? Before the plug change the engines were at their usual 165-168 in the slip. Do I need to be concerned? Should I pull them back out and back down the gap slightly?

3. If I replace the t-stats, what temp should I put in?
 

Maclin

Admiral
Joined
May 27, 2007
Messages
6,761
Re: New plugs causing engines to run hotter???

Did you do all of that at the same time then run it? Or did you do the risers and such, and ran it and the temp was as before, then put new plugs in and after that it ran hotter?

Engines that are running lean run hotter. Not saying that is a cause but may be a factor.
 

dsiekman

Senior Chief Petty Officer
Joined
Jul 7, 2010
Messages
798
Re: New plugs causing engines to run hotter???

She was running the usual 165 or so after the risers, manifolds, and circ pump. The temp increased after the new plugs.
 
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