Operating Temperature

[kwoolard]

I have a 1974 Mercruiser 888, 302 Ford I/O and have a question about the operating temperature of the engine. I have recently removed the manifolds and risers and cleaned them thoroughly in muriatic acid. After cleaning the water flow through the manifolds and risers is great. I replaced all hoses, the thermostat housing and the raw water pickup impeller. I took the boat out this weekend and everything seemed to be running fine. The only thing that I noticed is that the manifolds got hot to the touch, the risers were warm. You could rest your hand on the risers as long as you wanted but you couldn't do that to the manifolds. I have installed a 140 degree thermostat. I just do not know what temperature the engine is running at. On the older styles the temperature gauges did not have numbers, just a color coded gauge......yellow (cool)...green (mid range - operating range I assume)...and grey (high temperature). The engine was running in the green range a little below the grey mark on the guage. Does anyone know what temperature range was on these guages and what operating temperature this engine model should be operating at? The only good thing was that the engine held continuously at that temperature gauge location. Also, what aftermarket gauge and sending unit would work best with this engine?<br /><br />Thanks

 

[russman]

Re: Operating Temperature

i have the same engine #888 302 1976<br />last weekend mine never got above 160 and that was after trolling for 1-2 miles.<br /><br />when cruseing around it stayed just above the 140 <br />mark on the gauge.<br /><br />F.Y.I.<br />i did have a new impeller installed this year<br />and the needle on the gauge is in the middle for 160<br /><br />hope this helps<br /><br />russman

 

[crazy charlie]

Re: Operating Temperature

Is it a fresh water cooled or raw water.Raw water should be down 145-165 fresh water is closer to 180-190.Sounds like your guage has you close to the hot mark.The manifold will be hotter than the riser.If you split the riser from the manifold hopefully you did not use too much sealant on the gaskets.That would make it run hotter.Get the $20 telflex guage at any west marine or boaters world.Change the sending unit too.Charlie

 

[kwoolard]

Re: Operating Temperature

The motor is raw water cooled. I have center riser manifolds however they are still plumbed like the original log style manifolds were ie. water in the back of the manifold, out the other end of the manifold, into the thermostat housing, and then out to the risers and through the exhaust. Not sure if that would make a difference or not. Therefore, between the manifold and riser is a block off gasket. I guess that I will go ahead and get a new gauge and sending unit. I also have another gauge that is installed in the intake manifold but I don't think that it is extending deep enough into the water passage way to get an accurate reading. However, that guage didn't exceed 150-160. But like I say, it took a couple of adapters to screw it to the manifold so not sure if it is just reading static water.