OK so the over heating continues OMC

[Alexo1us]

For those of you who have been following I had it fixed for a day. I'm beginning to think it is the output side of the lower unit.<br /><br />Here is what has been done,<br />First I fixed the lower unit water supply then several leaks that developed in the thermostat area thermostat was replaced. After two outings I discovered two cracks in the water chambers on the manifold no water in places where it is not suppose to be, so I thought I would try the cold weld stuff this work great BTW sealed it all up.<br />During this process I had taken every thing off to the block to make sure I got it all. Even took the water pump off to inspect it replaced the belt since it was on it's last legs cleaned out all the parts got a gasket kit (no water pump gasket)<br />Started it up on the muffs and now it runs to the 180/190 mark never did this before. Didn’t go higher but before with the leaks it would run about 160 on muffs or in the water but on WOT it would climb to 240 on the water before I pull her back to cool off. So there is no point to take to the lake to see what happens at this time.<br /><br />When she is running now there are no more inboard leaks and there is lots of hot water coming from the area between the lower unit and intermediate unit where the two join but very little coming from the exhaust holes in the prop area.<br />All the flow rates are right according to the book. And it makes sense the guy who had her before said, if he lifted the lower unit with the tilt off the bottom it would cool fine, if there was a blockage in the exhaust side of the lower unit, as it would block the flow and when lifted it would flow fine as there seal between the lower unit and intermediate unit would be broken.<br />One thing though and I’m going to get some heat test sticks to see what happens, but it just didn’t seem to be that hot when I touched the motor. <br />Strange but true must be OMC.<br /><br />Any thoughts would be appreciated<br />Alex

 

[walleyehed]

Re: OK so the over heating continues OMC

Have you removed any miising impellor blades from the oil cooler side (if it has one).there also may be pieces stuck in the T.Stat housing that you can't or haven't seen, restricting flow.<br />One more item, a regular automotive thermostat will not work if you have a lake-cooled engine, the T.Stat must be made for marine applications...they have a very small hole that keeps water flowing ever so slightly even with the T.Stat closed.<br />If the engine has really got to 240 degs., I'm betting you have removed the temper from the rings and may experience oil usage from now on.<br />Lets hope your temp gauge is off...remove the connection at the temp sender and clean the contact area...high resistance may be giving a false reading.<br />Good Luck!

 

[cobra 3.0]

Re: OK so the over heating continues OMC

Sounds exactly like my 1986 3.0 OMC cobra! Same crap, whole new impeller kit, thermostat, and temp sending unit.<br /><br />Took off the riser, the manifold (and used some JB weld on an outer crack, checked every hose and flushed up and down, etc.!!!!<br /><br />It has great water flow gushing from the bellows and the prop. Water isn't hot, just warm.<br /><br />When I had her on the muffs, I let it go up to the high heat range, turned her off, opened up the t-stat area and put in a cooking thermometer to get a temp reading....160 degrees!<br /><br />Conclusion, my gauge is off.<br /><br />Are your risers hot? They should just be slightly warm. <br /><br /><br />For fun I will check around my oil cooler on the incoming hose to see if there are any impeller blades stuck there. Better sure than sorry.

 

[Alexo1us]

Re: OK so the over heating continues OMC

I now have all the leaks fixed new belt all the water paths have been cleaned and the water is flowing where it should be. The gauge now shows 195 and moves up to just under the 240 mark. But I can touch the thing I can even put my hands on the hoses and hold it there for short period of time. The question I want to know is if it was this hot I shouldn’t even be able to touch it should I? <br />The riser is hot on the exhaust side but cool on the inflow side I can touch it but can't hold for anytime but water dosn't boil off it <br />I’m thinking that it might now be a problem with the sending unit maybe the over heating killed the sender? Can’t get one just now, but thinking about putting her in the lake to see what happens<br /><br />Thanx for the input I will clean the wiring to be sure also maybe an issue with water pressure for the muffs.<br /><br />Alex

 

[cobra 3.0]

Re: OK so the over heating continues OMC

Cut the water and the engine simultaneously when it reads 240. Open up the t-stat area and dip in a cooking thermometer (cost about $3.00 at Walmart). If it reads 190 degrees or more, you have a blockage.

 

[Alexo1us]

Re: OK so the over heating continues OMC

The saga continues.<br /> I'll get this thing if it is the last thing I do. Did a complete go over all areas that are cooling related got a mechanical gauge installed will re install the original since it is working correctly and did some more testing. Then took her out for trial this time boy talk about a fun ride first putting in the water some how by the time I got to dock from parking truck boat was turned around with back facing in. helper forgot their was a back rope. Not a good start. <br />Anyway after the tilt not working as planed had to persuaded her then the starter not working from the key had to use the universal key. She started and ran up just fine so we took her out there is a little ways to go until wake is allowed but the hole time she ran cool 160. Get her to where I can give er take her up to 2000 rpm still rock solid at 160 ran this way for 10 min just checking over things discovered a slight leak at the down spout where it joins the hose to the exhaust outlet tighten clamp resolved this. Ran her up to 2500 this to produce no ill affects. Ran her for only a few minutes. From stop took to WOT she ran to about 4500 RPM 38MPH then after a minute maybe two she started again with the over heating let her run to about 200 gauge then shut her down to idle but she drop right back to 160 almost instantly. After several different tests I discovered that she will run at 3000 before the temp starts to climb again but as before as soon as I get her below 2500 the temp drop is almost instant back to 160 during the whole outing not once did the Engine ever exhibit any other signs of over heating.<br /><br />I was thinking, I know not a good thing although I didn’t try it for myself that since the thing stops doing the over heating when it is tilted up slightly. This was what I was told by the previous owner this would break the seal between the lower unit and intermediate housing allowing the exhaust and water to flow better. So I started thinking I missed something in the lower unit. So off she came again found the exhaust passage was completely clear upon careful inspection I found the front of the casing to be damaged from the exhaust and there were gaps bigger then should be. Thinking this may be a problem caused by the water pressure at high speeds getting though and causing a blockage I know a long shot but now I’m grasping at straws. So I sealed it up with silicone I know it is not required here but it won’t hurt ether. Found also some block passages one leading down to the prop exhaust from the top of the trim tab area on the lower unit two in the upper lower unit leading to where I assume are around the water pump area. <br /><br />But when I started it up again on the muffs still get very little exhaust flowing out the prop area most comes out between the connection between the lower unit assembly and the intermediate where they join. I have noticed just today that there should be a gasket there, mine has none. Could this be the problem?? Also on mine there is an access hole in the front for greasing the swivel bearing in all the diagrams I have seen there is a plug that is suppose to go in there but mine wasn’t even threaded so when running some exhaust and water flow out if here as well but it sits just above the bottom of the transom so I do not think water flow is a problem here other then I do not believe exhaust should be allowed out of here ether I was thinking of threading this and sticking in a plug.<br /><br />Could this problem be related to flow still I know all the water going in is coming out the back although most where the gasket should be about 70% and about 10% at the hole where the plug should go the rest at the prop could this be creating back pressure at speeds I was thinking since It make take awhile to get a gasket to use a bead of silicone around the lip make it thick and let it dry completely this would make a make shift seal that would test this theory and could be pealed off easily when the gasket is found. Even with all the work today I still feel it will do the same but it I get the seal between the two this will drive more of the water and exhaust down through the prop and when I seal the access hole with a plug it should all go down to the prop. I’m thinking this is needed to provide an easy flow.<br /><br />Sorry about long post but I wanted to explain the best I can. I guess I’m looking for more thoughts that would help me to know ether I in the right direction or way off the mark.<br /><br />For those of you make it though to here, any help would be appreciated as always <br /><br />Alex

 

[cobra 3.0]

Re: OK so the over heating continues OMC

If you have a manual and refer to items with there real names, it would be so much easier to understand what you are writing about.<br /><br />The "connection between"? Are you referring to the exhaust bellows that has slits in it? It is just fine that water comes out more there on the muffs.<br /><br /><br />Here are some diagrams:<br /><br /><br /> http://www.sterndrive.info/id10.html

 

[Lou C]

Re: OK so the over heating continues OMC

If it cools when you tilt it up and heats up when the drive is down, I would check the hose that goes from the outdrive through the transom mount. Sounds like some how it is kinking when the drive is trimmed down, restricting your flow.<br />Your heating problem as you describe it sounds like a lack of proper flow through the manifolds and risers, how old are they, did you check the risers and manifolds for restriction.<br />BTW, go to a Johnson/Evinrude dealer and get an OMC shop manual for it, best money you will ever spend. Lots of steps to check cooling problems.

 

[Blk-n-Blu]

Re: OK so the over heating continues OMC

Alex, What you seem to be describing is in my opinion a classic example of "engine circulating pump" failure not RwC pump. When on the muffs you are forcing flow through the system with the hose pressure.<br /> I know you mentioned having checked the pump and belt but were you able to physically check the pump impeller? you usually can't see it through the hose fittings.<br />When you operate at low speeds the block is full of water and make-up is achieved with the O/D pump. When at higher speeds the water is boiling off faster than it can be replaced. Just my $0.02

 

[Alexo1us]

Re: OK so the over heating continues OMC

Great input so far <br />The connection I'm speaking about is the two mating tubes for lack of a better term. My manual doesn’t describe them with any terms other then to say there should be a gasket and a locking ring of some sort. I have a stringer drive so there is no bellows to connect the exhaust to the lower unit the parts just come together. But there is allot more coming from this area then I think there should be. <br />As far as input flow there has to be enough since it cools fine most of the time and it will cool when tilted up but this destroys the ball gears. But I should think that if it will cool when in this position and since in this position all flows out the gap created <br />I would assume the blockage to be in the lower unit somewhere but I checked this and it is completely clear right through to the prop housing. The other thing about this that is strange that the dam thing drops right back to normal almost instantly so if there was a problem internally with a blockage I do not think that <br />1 it wouldn't cool down as fast <br />2 I don't think raising the lower unit would cause the over heating problem to go away. But having said this I have taken off all the parts related to this and cleaned and tested them and all the flow rates are better then the book calls for.<br /><br />And I have checked the circulation pump what car mechanics call the water pump it is fully serviceable had it off too. I still believe the problem is out back behind the transom some where If they designed to have a gasket they must have intended for this area to be some what sealed. Down it would seal a bit but maybe with the gasket not being there it is creating some sort of back flow in this area I do not know for sure I'm just guessing at this point. But for sure it is not in the water intake part and my riser and manifold is clean and flowing water at the correct rates.<br /><br />I should also say that the gap created by the exhaust forcing it self out the front of the lower unit where the gear case (lower) meets the top part of the lower unit was fairly big I think that this may have caused a higher pressure inside the case during high speed this would also block the flow I have now sealed this but as of yet had it out to try it, running on the muffs wouldn’t tell me this. <br /><br />Keep your suggestions coming no matter how unrelated it may seem it just may make something click.<br />One other thought just came to mind I did notice my WOT only gets to around 4500 what should it be I'm thinking it should be in the 5200 range maybe she is lugging as well. This boat has had allot of Idiots working on it before I got to her and she did have allot of problems with leaks and stuff that needed to be addressed and she is a lot better now then she was. There is more work to be done after I get the cooling fixed but at least I started on the biggest problem first I hope.<br /><br />Thanx again and keep them coming <br />Alex

 

[Alexo1us]

Re: OK so the over heating continues OMC

For those of you have shown interest this one will be shorter.<br />I can't get over that gasket thing But I have been thinking that people spend lots of money getting exhaust tuned and from what I saw here the flow wasn't right.<br />So tonight I got a plug for the service hole and made a makeshift gasket out of silicone high temp good to 700 so if it burns I have gone to far. if nothing else it will be a good test. If it dosn't hold nothing lost but it should last for at least one run.<br /><br />Will let you know how it works<br /><br />Alex

 

[Boomyal]

Re: OK so the over heating continues OMC

I think you may be making this more complicated than it needs to be. You have an OMC stringer, right? What year and model of engine?

 

[Alexo1us]

Re: OK so the over heating continues OMC

Originally posted by Boomyal:<br /> I think you may be making this more complicated than it needs to be. You have an OMC stringer, right? What year and model of engine?

For sure <br />But thats the way I think I try to guess all the different stuff that may be related and elimiate them one by one. This is how I end up at the back. All the other possabilities have ether been clean, fixed or repaired.<br />If this dosn't work I guess I start all over again. <br />In my line of work most of the times it is most likly the thing you just wouldn't think of normally that causes most of the problems.<br />shes a 1982 120 HP <br />I will know more tomorrow after I get her out.

 

[Boomyal]

Re: OK so the over heating continues OMC

ALEX, WHAT BRAND OF MOTOR?

 

[Boatist]

Re: OK so the over heating continues OMC

Alex<br />If this is a 1982 120hp series 400 OMC Stringer it is not that hard to troubleshoot over heating.<br /><br />The gasket between intermediant houseing and the upper outdrive will have no effect on over heating. It function is to force exhaust gas down and out the prop. This stops exhaust gas from leaking up at the stern and getting the back of the boat black from exhaust.<br /><br />Your systoms are classic plug exhaust manifold or plug up riser. Basicly restricted flow so when you need a lot of flow to keep it cool it over heats.<br /><br />Follow these steps and you should be able to isolate your problem quickly.<br /><br />1. Take the hose off the thermostat houseing that comes from the outdrive water pump and run it over the side. This need to be done on the water or in a tank, not on muff. At high rpms this should have flow like a garden hose. Good flow here then you outdrive water pump is ok.<br /><br />2.Find RPMS where the motor over heats and warm it up. Take the hose off that goes from the thermostat houseing to the exhaust manifold. This water will be warm or hot if overheating so be careful. You can put in a T and set up with one hose going to the thermostat output fitting, one going the exhaust manifold, and the third going to a shut off valve and then over the side. Shut the valve and run motor until starts to over heat then open the valve. If problem is a plugged up manifold or riser the engine will cool real fast but the exhaust manifold will heat up. Without the T you can just hook up a hose over the side and go for a test run but remenber no cooling to the exhaust manifold. <br /><br />If the motor still does not cool you have one of three problems. 1: The thermostat did not open allowing hot water to exit the engine. also make sure the small hole in the thermostat is not plugged. This hole allow air to excape so water fills engine up to the thermostat. 2: The engine water circulation pump is not sucking in cold water and pumping it into the engine so it can exit thru the thermostat when it opens. 3: The hole under the thermostat top cover to the starboard side of the thermostat is plugged up or blocked with a gasket. This hole is where the engine circulation pump sucks in it cold water to pump into the engine. It can get plugged with rust and scale but have also seen people make there own thermostat cover gasket and not cut out a hole for water intake.<br /><br />If the motor cools when you open the valve then you hava a blocked manifold or riser. This is very common in saltwater engines. Usually the block will be at the output of the exhaust manifold or the input to the riser. Rust and scale most common blockage. If this is the problem you can remove the rust and scale and it will probably be ok but this may also mean exhaust manifold near point where water will leak into the exhaust passage and down to the valves into the cylinders. May be a good time to change the exhaust manifold and riser.<br /><br />I have never here of any other OMC that would cool when Motor tilted and overheat when down. Still to test with the motor stopped tilt the outdrive enough you can put a water hose in the 4 inch exhaust hole and turn it on. Water should flow out the prop.<br /><br />This should at least isolate where the problem is.<br />Please come back and tell us what it is. My money is on the exhaust manifold and riser.

 

[Alexo1us]

Re: OK so the over heating continues OMC

Boatist <br />Thanx for the test procedure yours is a little more involved then the one in the book. <br />I can tell you that they were similar and I found the flow at the inlet hose to the riser will fill the gal jug in about 15 sec book calls for 20 to 25 secs then hose output from the manifold to the thermostat hosing is about 20 secs book calls for about 25 to 30 secs and last the flow back to the manifold from the thermostat is about 28 sec book calls for about 30 to 35 secs.<br />This test was done on muffs and at idle I can say the manifold on both sides intake and exhaust are clear had both end caps off can see right through to open air nothing inside. The riser although due to the bend can’t see though I have put a coat hanger though it and this to although at first was difficult to get through was eventually made clear by a good soaking in acid and a spinning coat hanger. The one thing I should mention here is during the install although I wonder about the gasket between the riser and the down spout on the down spout one side of the riser is blocked since this is how the water flows in but in the gasket kit there are two gaskets for this area. One completely covers this area and the one that the book shows to be installed is open here and on the down spout there is a small channel that is cut through to the exhaust side I think this is to allow for the water to drain from this side of the riser when off so I do not want to plug it and it doesn’t seem to bother the flow rates as you can see. The impeller in the out drive was replaced but the old one is still in very good shape and would have been good for service already had the new one and had it apart so I replaced it anyway. I know the flow is good to the back.<br /><br />This was a process as when I started I started from the back and work forward fixing every leak that appeared connections and such. Now there are no leaks inboard so what ever water comes in goes out the back but most of it is coming out the joint between the lower unit and intermediate housing I would say 80% and the rest from the service hole for greasing the swivel housing and prop. At the prop is water only no exhaust.<br /><br />The book calls for a gasket between the lower unit and intermediate housing and a plug in the service hole mine has nether. Interesting note for this is I believe this out drive has been replaced with an after market one the gasket has some sort of locking ring to hold the gasket in place but on the lower unit there is no grove or another indication of where the lock would sit. And the book shows the plug to be installed is supposed to be threaded and there are no threads cuts to accept a threaded plug. <br /><br />And yes this is a very strange symptom and doesn’t make sense. So this is why I figured this fix I made a gasket form high temp silicone which may or may not hold for long and stuffed a pressure fit plug in the service hole. Hopefully this will hold long to test the theory which maybe way off base but I have to try it as I have said before there must be a reason they designed this area with a gasket and for sure even new it wouldn't completely stop leaking at the joint but it should certainly block it enough to force more the exhaust thought the prop. I should also mention hear I know the exhaust side of the lower unit is also clear I can see air looking up through the hole at the top of the lower unit to joint between the two. <br />The makeshift gasket should be dry by this afternoon when I will drag her down to the lake and try it out will let you know how it works out.<br />If not I start again from begining and I will try your method.<br /><br />Alex

 

[marlinempress]

Re: OK so the over heating continues OMC

Like boatists said....<br /><br />"The gasket between intermediant houseing and the upper outdrive will have no effect on over heating. It function is to force exhaust gas down and out the prop. This stops exhaust gas from leaking up at the stern and getting the back of the boat black from exhaust."<br /><br />I have an omc 800 which has the same gasket that I ran for a long time without it in place and the only effect it had was making the back of my boat black until I put it on....

 

[Boatist]

Re: OK so the over heating continues OMC

Alex<br />Sorry I had forgotten that the 120 cooling system was different than the 140 HP. Still if on the water you pull the thermostat output hose and run it over the side and it has good flow the engine should cool fast. Since you correctly point out that input water also go thru manifold no danger of manifold over heating.<br /><br />Checking the water pump on muff does not tell you much as hose pressure can make everything look good. Pump operates in two different ways. At low speed it is a displacement pump and at high speeds it is a centrifical pump as the blades bend back to point they do not touch the sides.<br /><br />My 3.0L 140 the big gasket between the intermediant houseing and the outdrive has been bad for years but has no effect on cooling.<br /><br />Are you sure it is overheating? 240 degrees you should see steam.<br /><br />If you have good water flow thru the engine and it still over heats then check the timing. Last could have a exhaust leak into the cooling system and at high pressure of the power stroke be leaking hot exhaust gas into cooling system.<br /><br />Look foward to hearing what the fix is.<br />Good Luck.

 

[Alexo1us]

Re: OK so the over heating continues OMC

Boatist <br />Yes they are different but I must say that what ever I did didn’t solve the issue we had a good run had to keep her at 2000 RPM at the most before she would climb<br />Although not as fast I can actually let her run flat out for about 10 mins at a time. She gets to 38 indicated it runs at 4000 rpm is this too low and she seems to be bogging out of hole. She was enjoyable anyway. And I got to say she is very good in the water. It started to get choppy on the lake I was watching bigger boats getting bounced around. Even when flat out she ran flat and steady. I hate the hard jolting, this was a joy.<br /><br /> I will try the hose thing you may have something about the pump though and running flat out the input flow may not be enough.<br /> I’m going to take the thermostat out and see what happens. I do not think it here but at this point I will try anything. If nothing else it will make it a little easier on the motor and give me some more testing time before I have to pull her back since I won’t be starting out at 160.<br /><br />Could also have something about exhaust leaking into the water could be an internal crack in the manifold she did have external ones and higher pressure could cause it to blow in but not be big enough to cause water to get back into the engine. I will devise a way to pressure check it. Or if I can find a better one cheap maybe time to think about changing it but it just a lot to spend if it doesn’t work so I want to be sure.<br /><br />You also bring up another point about the 240 If the Mechanical gauge I had hooked up didn’t read roughly the same I would have thought the temp sending unit. But even so I must say that I do not see steam and I can put my hand on it and it feels just a little different then when she says she is at 160 I can hold my hand on it for longer input and out put hoses are cold exhaust being slightly warmer circulation pump hose is hotter manifold is the warmest with the riser being stone cold both sides so the flow below 2000 RPM is more then enough I should also add that when it runs hot the oil pressure is not affected by this. I should think I would see a drop in pressure at those temps as well <br /><br />I have checked the timing but it could have changed. What RPM should be WOT?<br /> I was thinking it should be about 5400 but having thought about this and only having outboards in the past I may be high. But in any case I do not think 4000 is right ether <br /><br />I think one of the external cracks on the manifold has opened up again there is water leaking down from that area also there is a steady drip right at the bottom of the back of the block where it joins the intermediate housing but this could be running down from this splashing from the down spout where it joins the hose guess it didn’t get it tight enough yet. <br />But are there (and please do not jump on me since I can’t recall the boating term for it). Freeze plugs back there I had the one on the right front just pop out looked ok to but I replaced it anyway. Maybe one of those, if any is leaking. <br />I will get this thing it may take awhile today’s ride just made me like her all that much more.<br /><br />On a funny note The place where we launch is a public place owned by the city and one of the things that tick me off is guys who just have cars taking up all the spots for trailers the one day I went down and there wasn’t one trailer there since the lot was full of cars signs everywhere but they seem to think they can ignore them. Well today I had no trouble finding a spot they were tagging and towing just had to wait for them to grab the cars and go normally I would feel some sympathy for them but being on the other side I didn’t. Boy it was good, tow trucks lined up coppers all over the place and people looking for their cars. There were some tense moments for the coppers though. <br /><br />I guess seeing some one else having problems at the same time made mine seem less.<br /><br />Thanx again for input please keep any thoughts coming they all are of help to me and possibly others that may read these adventures <br /><br />Alex

 

[Boatist]

Re: OK so the over heating continues OMC

Alex<br />If you have a pushed out freeze you could also have a cracked block, head gasket or head letting exhaust excape into water inside the engine. <br /><br />Sounds like you have a nice boat if you can solve the overheating.<br /><br />I belive the max WOT RMP range is 4200 to 4600 RPMS the same as the 3.0L 140hp. Going down 2 inches in prop pitch would put you at 4400 RPMS but i belive you would loose 3MPH at top end. I might run slightly cooler thou.