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Not overheating but just too darn hot!

1

1973 Browning Marine

Regular Contributor
At the beginning of season, posted about an impact I had doing a stupid water test on a local river. (What a hell hole that turned out to be!) Anyway, knocked a hole in lower unit case and limped back to dock. Bought another used lower, installed new water impeller kit with housing, reinstalled, etc.,etc. Started boat on a hose setup and after about 10 minutes I looked at the gauge and it was pegged at 250 degrees. I stated all of this stuff on my initial post and have not had time to follow up on it until today. (never really got in the water this season except for the stupid water test!) My concern is that I cooked the thermostat when I overheated. What do you guys think? Would those temps. possibly cause the thermostat to fail. This is what it has been doing intermittantly on the trailer since I have had this problem:
1) I ran engine probably ten times since installation of lower and the gauge slowly creeps up short of 200 degrees. Sometimes it stays at around that temp. And then occasionally, the needle will drop ever so slowly back to around 180 degrees. One time, when I started engine, it climbed just short of 200 and then shot down to like 160-165.
2) It seems like when I give the engine a little throttle, the temps. come down from like 195 degrees down to say 180 degrees.
3) I also found a piece of impellar in the heat exchanger cold water supply side which makes sense. I had problems with the used drive that I had purchased with respect to the water impellar. Stated that it had a new impellar with the used lower unit. (Alpha One Generation One drive and 1988 3.7lx 180 hp) When the accident happened, there was not any overheat issues. The engine did not overheat until I installed the replacement drive with a so called new impellar. Anyway, I trusted the guy and got screwed on initial startup on trailer. The engine at this point overheated immediately and reached 250 degrees. Changed impellar and housing and I am still running awful hot especially considering there is no load on engine on trailer and it will run even hotter in the water.
4) I have ordered a new 160 degrees thermostat and have not removed thermostat housing yet. I was wondering if it is possible for impeller debris to reach the thermostat housing and possibly hold the thermostat closed. Or worse, I simply cooked thermostat and it is now only partially opening. Make sense? I am planning on doing a full service: oil,filters,etc. before taking boat out for the rest of the striper fishing season but cannot do so until I am convinced that the boat will not break down. It never ran at these temps. on the trailer before the incident so I have to try and hopefully eliminate this problem.
5) I also had the 4 inch heat exchanger cleaned and just reinstalled today. Also noticed that impellar is delivering a good supply of raw water to the exchanger at this point.

I gave you guys as much information as I could and sure could use some help, ideas, anything!


I know I got the engine hot but I don't think I damaged the head gasket and all that nonsense because why does the temp. go back down once in a while. I am not loosing any coolant and the engine sounds pretty darn good but just seems to be running 15-20 degrees hotter than it did before on trailer. thanks, Tom
 
I simply cooked thermostat and it is now only partially opening.
Click to expand...
Tom, that is highly possible. Impeller chunks can't get to the coolant side of the system...no direct connection. You might perform a compression test just to rule out a damaged head gasket due to the high temp it reached. You will get a look at the plugs at that time.
 
Thanks guyjg for the quick response. I don't know what I was thinking about when I asked about the impellar in the thermostat housing. I feel like an idiot! Oh well, I guess I am overthinking it and it has been a long day. Of course, the raw water and coolant are separated! Brain fart! lol Just really worried about the head gasket because it is a pain in the ass to fix as well as expensive so I am kind of having a panic attack! lmao!. Let's hope I am still good in that respect. Don't feel up to tearing this beast down again. I should have the new thermostat sometime this week. Will let you know what happens after installation of new thermostat. I will also check condition of all plugs and I do have compression tester. Ok, now I am feeling a little better!lol Just want to try and salvage fall striper season in New Jersey. Will take a few weeks to really go over everything on the boat because of lack of time with work and everything else. thanks again guyjg, Tom
 
Tom did you check the flappers ? That hot they melt off and drop and clog the exhaust seen that plenty. I live in NJ. You come fishing with myself and my son if you want.
 
Master mechanic, the first thing I did was to see if the flappers were melted down obstructing the exaust system. That was not the case and the flapper was still intact. However, it had a bad case of sunburn! lol I will be replacing the flapper for the reasons you stated above. I live in the Philadelphia suburbs so you are not too far from me. I really appreciate the offer to fish and don't be surprised if I were to take you up on it! lol I would like to find out what the heck is going on with my boat first so as to have some chance of getting it seaworthy again. If the thermostat doesn't change anything, I will be pulling the lower unit again and checking every component again. kghost also stated that it is wise to remove pickup tube base attached to upper unit which is a kind of choke point for debris from impellar debris. I think he said to even try and force a hose from the heat exchanger side and try and force flow the opposite direction back down toward drive. I will definitely try this and see if anything comes out. I still want to do a compression test and visually inspect the condition of the plugs to try and determine head gasket condition. Kghost hit the nail on the head in an earlier post. I dread having to take that cylinder head back off along with all the voodoo nonsense associated with reinstallation. Just a real pain in the arse! lol Also, takes time because it has to be done in phases to be done correctly. More time that I do not have at this moment. Anyway, no sense of saying another word until I get into this thing a little deeper. Appreciate all the support from you folks and will let you know what comes of all this nonsense. talk to you soon, Tom P.S. I know about the screws possibly breaking off where the pickup tube mounts to upper. However, I did have them out earlier this season so I am hoping that things will go well in that respect. Wish me luck, I need it!
 
Raining here in Philadelphia suburbs. Got a chance to pull thermostat and sure enough it failed horribly in hot water test. I think I am on the right path now but still not out of the woods. I dropped coolant,oil,filters,etc. since the engine got hot just to visually inspect everything real good. No water in oil, a little bit of fines came out of the lower brass fitting in the bottom of coolant system which is at the lowest point. With 470's this is very important so none of that crap is getting up around cam seals and you know the rest. Nothing rusty looking in the cooling sytem either. Looked for the most part clean. I have not had a chance to remove plugs to see if there is any signs of steam cleaning in any cylinders and will do so if the rain lets up. There was also no coolant in oil and it seemed to be about 5-6 quarts. It looked dark and definitely needs changing also. I have one problem with the 14lb cap on the top of the cooling reservoir. It never releases into the overflow container and never really did. I cleaned out the hole where the hose hooks up under cap so it is not clogged. I am holding coolant and was wondering if I should replace the cap and what would you guys recommend. It has a 14 lb. cap and it is the original that came with engine before rebuild. Still waiting on thermostat so everything has come to a halt. thanks, Tom P.S. I did have flow on trailer to the heat exchanger because I had a leak on one of the ends of the 4" exchanger. I also removed the hose to the exhanger coming from the impellar. It has what I would say, decent flow but not like a fire hose or anything at high idle. I did not run any faster than 1500 rpm but there is flow. How can I test the flow from impellar? What should I be seeing with respect to volume and time? Or does this have to be done while in the water so there is no force from hose setup? Lots of questions but I'm not skipping a step this time! lol
 
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Replace the cap...it failed. I think the impeller should fill a gallon bucket in 20 seconds. I lower the drive into a plastic barrell full of cold water...the kind you can set a 1/4 barrell of beer into to chill it. Just let it idle for 10 seconds to see if it can fill the gallon 1/2 way.
 
Alright, finally got the 160 degrees thermostat in tonight and changed oil,coolant,filters etc. Ran boat at around 1500 rpms until warmup. Temp. slowly crept up to 195 degrees. I brought the engine up to 2000 and within a few seconds noticed that the temp. came down slowly to about 160-165. Brought back to a high idle say 1100-1200 rpm and it started creeping up to about the same again. Also, after warmup, I put my hand on the heat exchanger and it was too hot to touch for more than three or four seconds. Never seen it this hot before. I have come to the conclusion that the thermostat was definitely shot and the new one helped a bit but I still have to remove the lower unit and check upper part of water tube and to the heat exchanger for blockage. I also noticed the little pee hole on lower unit that shoots a stream of water out when the drive is hooked up to ears and running has a wide stream of water and does not seem to be pushing as prominent as it once did. (not a narrow stream anymore). I am forced at this point to remove lower and do as kghost suggested. I was hoping it was not the case but now I know it has to be either the water pump impellar,housing, water tube, blocked upper water tube housing, or blocked hose within the gimble housing. Everything was good until I damaged lower unit and apparently I am not getting enough raw water flow into exchanger and rest of system. So, that is where I am at the moment. Oh yeah, I checked power steering cooler, heat exchanger and the only one with rubber was the front side of heat exchanger. (entry side of course) The power steering cooler was clear. When I get a chance, I will post if I find anything in lower unit. talk to you later, Tom
 
Replaced entire water pump assembly and the boat stayed at 160 on the trailer for over an hour. Water supply to heat exchanger is fantastic now. Can hold my hand on exchanger for as long as I like. Nice! The flow rate to the exchanger is incredible. Bye the way, I bought an Quick Silver kit and replaced lower housing and I know now that it does make a difference and will never go aftermarket with the raw water pump again. The first aftermarket pump never produced as much flow as the one I just put in. Maybe I did something wrong on the first install but it looked correct. Definitely a positive result with the oem pump assembly soup to nuts! Thanks all of you guys for helping me out with this. Did not know what to do and I knew the boat was definitely not seaworthy running at those previous temps. Cant't thank you guys enough. I am so happy! Really good feeling to get it going right this time around! It was just as kghost had warned me and one pain in the ass pulling everything apart and checking but was worth every minute of pain to know it is finally running at the right temps. I knew something was not right for awhile and refused to take it out on water because I felt that it would definitely overheat under load within a few minutes. The temps. on trailer were just too high before I found the problem. Now I understand the importance of the raw water pump first hand and will change it every season if all goes well. (Maybe more often than that! lol) Thanks a million guys for all your support! Thank God, Tom
 
Tom, some people say every other year and others every year. I seen some go five years but I've never had trouble with one left in three years. Change it in the beginning of the season so it doesn't sit over the winter before use. Just pay attention to your gauges and keep using the IR laser temp gun on the heat exchanger, manifolds and T'stat several times a season...it only takes a minute to check temps w/one and before long you'll know the temps by heart an d will be able to detect the subtle changes in temps before a problem arises. Test the pressure cap annually...take it to an auto parts store...they all have pressure testers.
 
guyjg, that is the right way to do it! Totally agree! I do have a IR laser temp gun and definitely will be using it before I decide to go out with the boat. Gives you pretty good information at the press of a button. I did replace the cap and I think there is a pressure tester in my shop somewhere. I bought a 13 lb. cap because that is all the guy had at the parts store I went to. The old cap was 14lb. I think it calls for between 12-14. Sound right? I finally feel that I have a handle on things at the moment. I guess I will find out soon enough. Thanks again, Tom
 
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