Engine Runs Cold

[victoryinerie]

After replacing the thermostat, sender and several tests on the temperature guage I am convinced my engine is running very cold. I have run the boat in the water and with the muffs and I am getting similar results. The engine is running around 100 and than ocassionaly it will go up to 170 for a second and than it drops right back down to the 100 degree range.

The engine is a 1998 2 barrel, 5.7 Merc. Any suggestins where to go from here? The engine really seems to run fine, how bad is it too run cold like this? At the place I go for parts they thought that the riser should have a restriction gasket and if some one replaced it with the wrong gasket all four slots will be pushing water through. He thought this could be my issue.

It sounds like this could go places where I have not gone on my engine, is there manual I can pull to see what all this should look like if I decide to pull it apart. It appears to be four bolts on the top??

Any thoughts??

 

[victoryinerie]

Re: Engine Runs Cold

Along with this the boat has a Bravo III outdrive, the previous owner said he replaced the water pump.

 

[steve riddell]

Re: Engine Runs Cold

You never mentioned replacin the gauge itself, if it drops that quickly it sounds like you meed a new gauge

 

[victoryinerie]

Re: Engine Runs Cold

I had my hand about the themostat, the metal and it almost got too hot too touch, I asssume that was 175 and than it immediately dropped an got cold. After it dropped I put an IR gun on the sender and it read about 110. I also took a hot cup of water, with a themometer in it, put the sender in it and grounded it to the boat, they were about equal. Thereofore I have not replaced the guage.
Also a friend game me an old guage to hook up, I hooked up the power to the battery, ground to the batteryground and than too the sender post however for some reason the guage pegged out and stayed there I am assuming it was a bad guage to begin with??

 

[dubs283]

Re: Engine Runs Cold

if there are 3" or 6" risers between the top of the manifolds and the elbows, then the four-slot gaskets are correct

there is a service bulletin (99-10?) about engines with risers running hot and the fix is to install the four slot gaskets - also, this would not cause a cool running condition, i would only be concerned if the engine were running hot

the problem could be as simple as a sticking thermostat, i know its new but they do come bad from the factory, make sure it is the right temp t-stat as well

 

[victoryinerie]

Re: Engine Runs Cold

There is no riser there therefore should it be a 2 slot gasket? I am not overly concerned about running cold but it just seems to abnormal which means it could be some thing major and I would hate to cause more damage.

Is there a place where you are seeing this about the 2 slot and 4 slot?? If so can you let me know what you are looking at so I can do the same?

Thanks

 

[dubs283]

Re: Engine Runs Cold

with no risers, you should have the 2 slot gasket that has relief holes for the other two slots

i read the service bulletin as part of my job, i have no idea where to find it online

running the engine cold can cause carbon fouling on the plugs and in the combustion chamber due to improper running temp - aside from performance and having to replace plugs sooner than normal, i don't see any cause for major damage to result

i would still be suspect to the t-stat being at fault here, if you still have the old one, try running it with that one in

 

[victoryinerie]

Re: Engine Runs Cold

I am back at it again:
-I hooked up a guage right from the battery and to the sender unit and compared the two guages, the guage directly to the battery had alot more movement, it would work it way up to 160 and than go down to 100(under muffs), the one on the boat would only go to about 110 and than down which would make me think the guage is mis reading however previously I took a hot water 180 with the sender and a theometer and compared the two and they were just about equal?

What I thought was odd, when I hooked up the guage directly too the battery and shut off the engine, the guage would read around 130 to 150 ish, if I turned the key to the accessory, the guage would drop completely down? Would this be normal when hooked directly to the battery??

What also was weird when I hooked up the guage to the battery direct, the alarm buzzer in the front would slightly hummm? Not the normal warning sound.

Could all this be some sort of ground or wiring issue??

I noticed in the back of all the guages was a buss bar and mostly black wires are hooked into it? Is this some sort of common ground area? One of the wire looks like it was not connected in however I did not want to mess until I figured out what all this is.