Running without a Thermostat, big deal? What is this housing/manifold/t-stat thing?

[SoldTheBayliner]

Short version: a week of camping at the lake, boat started overheating (2000 SAN, Apex 5.7 motor)... I didn't want to believe it could be the impeller, because it's only a couple years old... so I pulled the thermostat thinking maybe that was the issue (I've run a couple old cars without them with no issues when they had overheating problems)... boat kept heating up, but not as quickly.... eventually pulled the impeller and it was indeed the problem. Replaced the impeller and got back to playing. But now the boat is running at a ridiculous 125 degrees and won't get anywhere near it's usual 160 degrees because of the missing thermostat. Other than missing out on a few horsepower, is this a problem? Basically I'm wondering if I should get after it and put one in there before the next trip in a couple weeks.

AND, the thermostat really threw me for a loop.... I've never replaced one in this boat (or any boat I guess). I was expecting to see a normal thermostat in there. This thing seemed to be a part of the thermostat housing, rather than a separate, drop-in, thermostat like in a car. I removed the housing (like a manifold with 4 hoses going to it), looked into the hole in the motor, and thought "oh junk there is already no thermostat in here"...then I looked into the housing and saw it, so I grabbed it and tried to pull it out... no dice. Eventually I got it out of there... in 2 or three mangled parts, and a bit of the 'skeleton' of the thing that was completely fused to the housing refused to come out, so I left it (it's not restricting water flow). Are these things actually a part of the housing? Like you have to replace that whole housing/manifold? That seems ridiculous. Maybe mine was just rusted/16 years of crud fused in place in there? I know it's not the common motor with the 5.7 Apex, but someone here can hopefully give me some clarity here?

Thanks in advance...

ps, would it have hurt anything to put a tiny bit of a bump in the back of the boat so that there's more than 2 inches between the impeller housing and the stern?

[shag]

Impellers should replaced every year just as maintenance. Your temp is low because you now have a very good water flow. As far a needing a higher temp, I am not an expert but it could even come into play with complete combustion and how the motor wears. Parts need to heat up to a certain extent to wear properly, but obviously too hot is not good either. If that thermostat had never been replaced then it sure can 'weld' itself in there, especially if you were experiencing high temps for awhile which you probably were if that impeller hadn't been replaced in years. Just my .02

[SoldTheBayliner]

The impeller was on it's 3rd year. I've always gone 4 with no issues, but I guess I was pushing it. I'll replace every 2 now. Yeah, good water flow with no thermostat is keeping things veeerrrry cool. Just wondering if that can cause any issues. I can't think of any other than loss of horsepower....

So it's a "normal" thermostat, just fused itself to that housing? I would assume that, but man it was stuck so hard I was convinced it was somehow a part of the housing/manifold. I don't see any thermostats for a pre 2003 5.7 engine on nautiqueparts.com. The gasket is shaped different than those ones for sure. If it's the same thermostat but a different gasket, I can make my own gasket, but I'm not convinced it's the same thermostat...

[DLafont]

Check Christinesmarine.com, they have thermostats for older boats

[a0128]

For best performance you are going to want to run a thermostat. Nautique Parts has them. 10% discount with the PND discount code.

[SoldTheBayliner]

Right, that's the 2002 and up one... mine's a 2000. I didn't see mine on their site. That gasket looks different. Is the T-stat the same?

[t.franscioni]

The thermostats fuse to the housing due to corrosion. I had to chip away thick rust and then use sand paper to get my housing looking normal again. Eventually had it sand blasted and then I could see all the original casting and machining marks from where the thermostat goes. Takes years of ignoring your thermostat to happen but if you want to avoid it you should pull your thermostat out at end of season and clean up any new corrosion as part of your winterizing practice. Even if you drain your block a little water gets stuck in the Tstat housing and will start the corrosion going over winter.

[SoldTheBayliner]

^^ Thank you, that's helpful... I've never touched it before, and the boat sat for a few years in a warm climate where it didn't need to be winterized. I've been winterizing, but haven't messed with the thermostat at all. I'll pull it back apart and clean that housing up. Sounds like it's just 16 years of crud build-up.


Still curious if there's any good reason to rush to get one in there... is running cool for a few days in the next couple weeks going to cause any issues? Wouldn't matter in a car.....

AND can anyone verify if that 2002+ t-stat for the 5.7 is the same size as the one for my 2000? In auto-land they're universal, but do they have different diameters or anything on boats? The gasket is obviously different, but I can make a gasket...

[t.franscioni]

While realistically yes you could run no thermostat, PCM doesnt put in thermostats just because. As noted in an above post the engines are engineered with specific tolerances between the various parts and heat expansion is taken into consideration in machining those tolerances. The engine will wear best at its designed operating temperature. As cheap as thermostats are id get one in there as soon as I could. Call nautique parts or skidim and they can make sure you get the correct thermostat for your engine.

[IMScarlet]

Most important point with fuel injection is that the ECU governs fuel metering based on engine temp so basically your engine is effectively running like you have the choke partially closed so long term the oil will break down quicker you will have increased bore wear and the valves/spark plugs will foul. For a short period of time to get yourself out of jail you shouldn't experience any real effect other than fuel economy

Sent from my SM-G900I using Tapatalk

[SoldTheBayliner]

^^ Good info, thanks. That makes sense.

I just got this follow up from nautiqueparts.com:

I have dug and found that the apex takes the same thermostat and gasket as the Python. Here is a link to it:
http://www.nautiqueparts.com/thermos...desgasket.aspx



That gasket definitely looks right. Who knew. I'll order that one and get it in there if it comes before I head out next week. Thanks again guys.