143 Thermostat question

Not sure why you'd need a stat with relief holes in it for these engines. Only time I've seen that done is for some diesels to improve cold weather warm-up because in around-town driving they wouldn't heat up enough to open the stat, and the heater core wasn't warming up.

Doesn't the thermostat housing have a relief hole cast into it?

wiscofoot wrote: Thanks guys, I actually bought the one in the link last year and then modified it kind of like Ken described. And yes I know I can make one, just trying to save some time when I unwinterize this weekend and try to efficiently diagnose and fix my issue with water getting by the closed thermostat and not letting my engine warm up and thus not letting me change my oil in the driveway. What I was more curious about is a definitive answer about the T stat, I've seen several conflicting answers. Do the marine thermostats allow more flow when closed than automotive thermostats? Did they come from the factory with holes drilled in them like some of the "performance" hot rod auto ones? Are they all stainless?

You'll get all kinds of conflicting answers on that t stat question.

They're not all stainless, they don't all have holes in them and they don't allow more flow when closed. unless there are holes drilled.

A PCM branded 143 degree thermostat is not stainless and has no extra holes

And besides, it's kinda tough to find a 143 degree automotive thermostat.

Buy a PCM 143 thermostat for the best chance of getting good results

Whaddya mean   "what" ?

What I'm saying is that if you go to the parts store and get the automotive thermostat gasket it won't work between the lower housing and the cover for the thermostat.

That gasket will work between the PCM lower housing and the intake manifold though. The automotive gasket has the medium size hole in it and that hole's not needed on the marine engine but the gasket still works between the PCM lower housing and the block

Maybe you're saying the same thing?

First picture is the cover gasket GREEN and a housing to manifold gasket BLUE

Second picture is one on top of the other

Wisco

You're a power plant engineer I seem to remember.

Go visit the maintenance shop and they'll show you how to make a gasket

Here a a few pictures showing what you need to do it the "backyard hack" way

So easy a caveman can do it, but he'd probably use a rock instead of a ball pein hammer

Put the upper housing in a vise as shown, put the gasket material on the housing and lightly bang away using the ball end of the hammer and you end up with a gasket.

All 4 holes can be done with the hammer only and if you want to get fancy you can trim things but it's not necessary

Don't worry too much about the outside edges, tap enough to get the outline then cut with a pair of scissors

1/32 inch gasket material from your favorite parts store (or maintenance shop) works fine. Ask for rubber fiber gasket material

For 6 or 7 bucks or so, you'll have enough material to make a whole bunch of gaskets or screw up once or twice and still have plenty leftover.

Then you won't have to buy a genuine PCM gasket or an aftermarket version of it.

The automotive ones don't work because the thermostat mounts directly to the manifold and there's no lower housing.....just the thermostat and the cover

So.................go for it, you can do it   

In this age of improvisation, I wouldn't hesitate to cut a gasket from loclly available gasket sheet stock, it's not like it's a head gasket, just warm water under low pressure

That’s like magic, thanks Keno!

Let Google be your friend and search correctcraftfan dash grounds and you'll come up with a bunch of reading

Perfectly normal due to inadequate ground.

Sorry for the confusion. Thanks for the help, I'm a novice when it comes to this stuff and I appreciate all the solid advice I get here.

gibson1525 wrote: Correct me if I'm wrong but the bottom of the thermostat housing and right next to the temp sender should read the same temp. I've been taking my temp readings from both those places every time and they are always very close. The top of the thermostat housing is always a fair amount cooler than the bottom.

Everything you wrote above is right.

As you mentioned it sounds like an electrical issue since all of your gauges are reading wrong   

gibson1525 wrote: Update I replaced the temp sender and no luck. It is still reading 180s when the thermostat housing is reading 140s.

8122pbrainard wrote: And directly next to the temp sender to see if it coordinates with the gauge.

You're not listening!!    The T stat housing is where water that's not needed is bypassed to the manifolds so, you may be reading where cool water mixed with hot.

I had a similar thing with mine where ultimately a new gauge was the fix.

Overall low dash voltage problems, common with these 80s - early 90s boats can cause wacky gauge readings as well. If all of your gauges dip when you blow the horn or turn on the blower or bilge pump, that’s a clue.

Brian - We would love to know what you find out about the sensor.

When you change it, see if you can find an ID #.

Either someone put the wrong one in, or it changed resistance due to old age.

Information like this helps everyone on the site.

SNobsessed wrote: Another thought - Maybe it isn't getting as hot as the gauge says? You could use an IR thermometer to check actual temp.

Suggested back on the 4th of Aug