• Welcome to the Checkmate Community Forums forums.

    You are currently viewing our boards as a guest which gives you limited access to view most discussions, articles and access to our other FREE features.
    By joining our free community you will be able to:

    » Interact with over 10,000 Checkmate Fanatics from around the world!
    » Post topics and messages
    » Post and view photos
    » Communicate privately with other members
    » Access our extensive gallery of old Checkmate brochures located in our Media Gallery
    » Browse the various pictures in our Checkmate photo gallery

    Registration is fast, simple and absolutely free so please, join our community today!

    If you have any problems with the registration process or your account login, please contact support by clicking here or by using the"contact us" link at the bottom of the page.

Temp Question and Oil Leak Question

J

Jamey

Member
I'm running a GM marine 350 in my Entertainer I/O. It's a 1980, with the original outdrive. My temperature gauge has a midpoint of 150 degrees, and a maximum reading of 240. At cruising speeds I stay just over 150, but if I hammer down on it, or if I putt along at idle speed, it climbs to around 200. Is this normal? What is the optimal operating temperature?

Secondly, I have an oil leak somewhere, and could use some advice for tracing the source. It's dripping off of the oil pan by the drain plug, but it's not coming from the plug itself. I've tightned down most of the oil plan bolts, and they were loose, but it is still slowly dripping. Over the course of a month about 3/4 of a quart dripped out, so it's very slow, and it certainly doesn't seem to be hurting anything other than to annoy me knowing it's there. It wasn't leaking before this year, and I put the engine in around 1996. I used it for a season and a half, and it's been sitting untouched until this year. The engine has less than 70 or 80 hours on it, so it worries me that it started dripping seemingly out of the blue. It didn't seem to leak until I changed the oil a couple of months ago. Anyone have any ideas?
 
Jamey Sounds like you may need a new impellar or water pump(when is the last tim you changed that?), should run 160 170.... It is probably def. leaking out of the oil pan gasket, only way to fix that is to pull the engine.
 
The impeller was changed this fall, so it is still pretty new. So there's no way to change the oil pan gasket without pulling the engine?
 
not a hope, unless of course you like standing on your head for a few hours - and even then you'll end up making a mess of things. is it possible that the oil pan has a hairline crack in it? had that happen to a car i had - i'd lose a litre in about 2 weeks - left a big oil stain in the garage but it was hard to find the leak - i racked that up to corroision - maybe you have the same issue.

sounds like the impeller is no good - or you have some debris in the cooling system - remeber, unlike a car you are running staight water through the cooling system and at 212 water boils - you're getting awfully hot for my liking. check that cooling system throughly.
 
What are the conditions of the exhaust manifolds and risers? They can certainly cause the overheat you described. The oil leak is anyones guess. There are too many places it can leak from for anyone of us to give you advice on. The only thing I can tell you is to look from the top of the engine down. See the highest point the oil is leaking from and take it from there.
 
I had brand new water manifolds put on this past fall while I was still restoring. It shouldn't be clogged. I checked with the mechanic who put the manifolds on for me and he didn't think it was hot enough to worry about. In fact, when it was running around 150 he thought that was too cool?
 
merc engines were running 2 thermostats one was 140 the other 160 - i can't remember which one was for which engine though.
 
if your fresh water cooled the older engines ran a 140 degree thermostat.. I have seen many things cause the issues you have brought up.. bad thermostat housing, which is corroded on the inside, exhaust manifolds, bad pop off valves, twisted hoses, thermostat.. best i can say is run it and shoot it with a heat gun to find out whats heating up first.. the wrong gaskets between the risers and exhaust manifolds will do that too.. ooohhh yeah... a circ pump will do that too.. your just gonna have to diagnose it
 
Seemed to do a little better this weekend for whatever reason ... it hovered between 150 and 200 most of the time, but it was consistent. Once while idling dor a while it crept up too high for my liking, but as soon as I got back to cruising speed it dropped back down to the 150 to 170 range. I'm wondering if the guy really changed my impeller, or if he just said he did it. The fact that it seems to do fine cruising along at around 35 to 45 mph makes me think that it's just struggling to take in enough water when it isn't being forced into the water pump. I'll probably drop the lower unit again next time I go up and replace the impeller just to be safe.

The oil leak turned out to be a loose valve cover! Easy fix ... I love those!
 
When you pull the lower unit off, pull the waterhose from the back of the powersteering cooler and blow water back thru the transom and upper drive to clear any old impeller debris out of the lines. also make sure to replace the impeller housing and the hose section from the pump to the upper unit.
once the t-stat opens, the engine should keep a constant temp regardless of throttle setting or speed---that is what a t-stat is for. check to make sure it has a t-stat at all, and check the 2 spring loaded checkballs in the upper t-stat housing
 
you probably don't have an impeller problem, how hot do your risers get? can you touch them ??? be careful don't burn yourself.. have you pulled the hoses off the thermostat housing?? to check the condition of your pop off valves and overall corrosion? have you pulled the water inlet hose off the transom assembly then thermostat housing and flushed it out?? this is normally where the debris will collect??
 
something else that it looks like we have all overlooked - water hose from the bell housing to the transom assy. they weather check, crack and leak. under water at low speed you don't see it, at high speed though - water will leak out the hose. check that hose!
 
All good ideas, guys! The manifolds get pretty hot, but not so hot you can't touch them for a second or two. All of these sound like better ideas than pulling that lower unit again. I think I'll check all the hoses, and maybe even remove the thermostat and run it for a day to see how much better it does. If that cools her down, I'll put another thermostat in it to make sure I have the right one. Thanks,
 
Jamey,
I had a similar problem with the boat I just bought. I knew this up front, the guy I bought it from told me it would overheat at idle. He had bought a new circulating pump to solve this, I told him unless the circ pump was leaking externally, it would not help and figured it needed a new impeller. I took the boat out that weekend and sure enough, the temp would slowly climb at idle, I didnt let it get over 180 which is way too high for a 350 MC. at speed, it ran 150-160.
So, I put a new water pump kit in the lower right after I bought it. I took it out again and it didnt seem to help much. Last week, I pulled the thermostat housing and replaced everything. I also installed the new circ pump while I was there. While I had the lines loose, I checked all the hoses for any restrictions.
Now it runs fine, about 140-150 at speed and 160 at idle
I dont know if it was the thermostat, the circ pump or possibly there was an air lock. I would bet the thermostat was sticking though.
Bob
 
Thanks Bob, glad to hear you got yours squared away. I hope pulling the thermostat and giving the hoses a good once over will straighten mine out too. It's just getting way too hot. I've been burned by a broken thermostat before (no pun intended) so I am hoping that is all it is.
 
You must log in or register to reply here.
Back
Top