Overheating even after the shop

Hey all Just thought i would throw this at you guys and see where it goes. I have a 1991 Supra TS6M Comp and it has an overheating issue. Thus far I have changed the impellar, thermostat, and even taken it to the shop. The shop gave it back and said "it was just a slight clog in the transmission cooling intersection." They said they ran it and everything was fine. I took it out for the first time since they worked on it and suprise suprise 220 sitting at the dock. Didnt even get it off the trailer. IT also has power loss big time (wont even plain) when it starts to get too hot (190 +) Engine is 351W PCM with Holley Double and electric ignition. The exhaust mainfold on the right side has heat exchange from engine while the left does not. dont know what else to look for.

Find the thread that Wotan started about an issue he had that sounds familiar. Have you tried running it on the hose in your driveway or where ever? If you are using a fake a lake, dump a hose from the fake a lake into a 5 gallon bucket and then dump your hose off the house into the bucket, that way you are supplying water but not under pressure. This way you can see up the impellor is able to create enough suction or not and if there is a possible leak in one of the hoses where you are sucking in air.

220 while idling at the dock is pretty extreme. Did you loose a impellor then the heating issue started? Happened to me unfilled I got all of the chuncks out of the pump grate (on its discharge side) and out of the hoses. They were tough to see unless you were looking for them.

An I would call the "shop" and tell them there a bunch of idiots.

I know for a fact that these engines can run without an impeller and just off of the hose pressure. My guess is that this is what the shop was doing. Look for my thread on my pump not priming and read through the whole thing. I can't tell you for sure that your pump needs to be rebuilt (and that's the last thing that I would try) but I did outline and exhaust every other possibility and tried to document it as well as I could.

Here's the thread. https://forum.supraboats.com/showthr...mp-won-t-prime!

Did they lake test it or fake-a-lake test it?

If you paid, take it right back and tell them to fix it right this time, and show them how to truly test it like Wotan does above.

There could be a number of things wrong. Also, what temp thermostat did they put in it? I've seen garage jockeys put an automotive t-stat in thinking it would be just fine, but once it finally opened up, the engine was too hot, and it was very difficult for it to cool down.

Tried all of that guys. I did the fake a lake/hose and bucket still overheats at idle it overheats very slowly under pressure it overheats very quickly. I just replaced the impellar before it went into the shop. I am very upset with the shop since they are one of the major players hear in Tri-Cities. When i picked it up from the shop the guy looked me right in the eye and said "it ran great problem solved" and then i asked him "you tested it under running conditions" he said "yep runs like a champ" So i am going to making a phone call to them and if they don't make it right i will be sure that nobody ever uses them again.

Something is def. up. When you hook it up with a hose (creating pressure through the system) -- does water come out the exhaust BEFORE you start the boat?

If water is making its way through the system without relying on the water pump, it should not overheat. Concentrate on getting to this point, first. Rule out that there is any blockages anywhere in the system and that water is cooling your engine. Pull all hoses and flush them out. Pull the thermostat and remove it for now. We can walk you through how to troubleshoot this if you're willing to do the work. It's not complicated.

It might be complicated when we get to how to fix it... but let's troubleshoot first.

Possible the hoses were reversed on the water pump?

copied this from another post--similar problem

"Pulled impellor and it looked fine until I looked at the brass interior...it was worn and spinning in impellor. Repalced and all is good now...Thanks! "

How long have you had the boat. Was it running fine and then it started overheating all of a sudden or slowly over some time? Please give us all the information. What did the impeller look like? How many hours on the boat. Does the engine suck water out of a pail? This is your first post , how about some history.

Okay So the Shop Fixed it this time They put the damn thermostat in backwards (idiots) But now magicaly I have a runnability problem which i didnt have when it went into the shop. When I go above 20mph the engine starts to cut out and if i really get on it it backfires and sputters and wont go above 20 mph. The Shop guy said my carb was gummed up. So I cleaned the carb with no results. This is also odd because when I first take off from a stop it has tons of power and quickly climes to 35mph and then starts to sputter and cough until i Bring the throttle back down to about 35%. Fuel, Spark, or What I dont know.

P.S. 1991 Supra 351W 4bbl Holley with electric ignition.

Thanks again guys for the help.

I just learned that the OEM water pumps should pump 9 gallons per minute. My original pump came nowhere close to that, maybe a couple gallons a minute. Tried tons of stuff, and eventually replaced the whole water pump. Worked for me.

Your new problems do sound to me (amateur) like a carb issue, but could need adjustment, a good cleaning, or a rebuild (new seals, etc). There is a quick check you can do on the "power valve" on holleys website if you google it. Have you ever had the engine compression tested? Good luck

I'd say fuel delivery. If it initially accelerates well then starts to cough it sounds like the float bowls are getting low. Check fuel filter(s). That really means change them if they haven't been changed recently. Then do a fuel delivery check on the pump. You will pull the fuel line off at the carb or somewhere after the filters and run a line to a container and see what you have for volume when cranking the engine. You should get a good shot of fuel every other engine revolution, no need to count engine revolutions btw. Just look for a good pulse of fuel and you should get a pretty good volume of fuel in say 15 seconds of cranking. I'm guessing a cup or so. What you want to be sure of is that it doesn't just pump a little bit and then barely trickle, if it does you have a restriction in the supply side of the system.