Thermostat problems help!!!!!

[sebas54]

Hi, I just put a new thermostat (142 degrees) on my 4.3l 1988 gm I/o engine. I took it for a spin and started to lose power, so I pulled back on the throttle and she stalled. I checked the Temp. and it was at 200 degrees. Disconnected the hose from one of the risers and there was a little bit of smoke (no water). So, I pulled the thermostat and startede her up. The engine cooled down right away and stayed below 100 degrees.

Can I run my boat all summer long with out a thermostat or just for a couple of days?

Also, when installing the thermostat the spring faces down, right???

Is it common to buy a defected thermostat??


Thanks for all the help!!!

 

[Don S]

Re: Thermostat problems help!!!!!

Hi, I just put a new thermostat (142 degrees) on my 4.3l 1988 gm I/o engine.

Is this a Mercruiser, OMC, Volvo? and what year. They have all different kinds of thermostat housings.

Also, when installing the thermostat the spring faces down, right???

Absolutly, SOMETIMES. (see above)

No, you do not want to run without the thermostat, in anything. It may run cool on the front of the engine around the temp sender, but not on the back cylinders. They would get little flow.

 

[sebas54]

Re: Thermostat problems help!!!!!

It's a 1988 merc. 4.3l alpha 1

 

[MikDee]

Re: Thermostat problems help!!!!!

Check your water intake hose from the outdrive, to inside under the motor, leading to the water pump on the front of the motor, to be sure it's not kinked at the outside transom plate (at the bend) this can occasionally happen, or for blockage somewhere. You can actually take it off the water pump at the bottom if need be to check for flow, on the garden hose.

 

[sebas54]

Re: Thermostat problems help!!!!!

I am going to change the water pump circulator tomorrow but the engine was running at 100 degrees after I took the thermostat out; so I think that I had a faulty thermostat.

Can I run the engine without the thermostst just for this weekend??

Thanks

 

[Don S]

Re: Thermostat problems help!!!!!

Can I run the engine without the thermostst just for this weekend??

Not advisable. Put a damned thermostat in it. It's a lot cheaper than an engine.

Why are you changing the circulation pump. Use the money for a thermostat and gasket. ................... Geeeeezzzz

 

[sebas54]

Re: Thermostat problems help!!!!!

Can I use an automotive thermostat??

I am changing the pump because it is leaking and it makes noise..


Thanks

 

[MikDee]

Re: Thermostat problems help!!!!!

Can I use an automotive thermostat??

I am changing the pump because it is leaking and it makes noise..


Thanks

Thats probably the whole problem, put the new thermostat back in then. It won't get up to temp on the garden hose.

 

[Coors]

Re: Thermostat problems help!!!!!

Do you have any broken impeller pieces in the system that you haven't mentioned?

 

[sebas54]

Re: Thermostat problems help!!!!!

The water pump that was leaking has no effect on the thermostat because I pluged it with water bond.


I was just mentioning it because I was asked.


I just changed the impeller, so no there were no peices anywhere.

I pulled the t-stats and the temp went down right away.

I am not runnung the engine on a garden hose.


The T-stat, I think is faulty. It never open.


Is this something that happens frequently??

Can I use an automotive T-stat?

Thanks

 

[Lou C]

Re: Thermostat problems help!!!!!

You can't use an automotive thermostat, they are set to open at a higher temp than your raw water cooled marine engine is supposed to run at. Plus it won't last in a non-antifreeze cooling system. Any West Marine or Boater's World, or any decent marine parts store will have a thermo for a Mercruiser. I test them before I put in a new one, by hanging it by a coat hanger in a pot of water, I have a radiator thermometer and I heat the water and watch at what temp it opens, most later models the thermo is a 160 and it will open at about that temp. If you don't have a thermometer, you can still test it, it should be compeletly open well before the water in the pot boils. Make sure all the passages in thermo housing are open and not plugged by corrosion. Briefly check the impeller by disconnecting the raw water intake hose at the thermo and starting the engine with the boat in the water, while someone holds the hose up in the bilge. A good stream of water should shoot out. If not you still have impeller problems or a blockage.

 

[45Auto]

Re: Thermostat problems help!!!!!

Defective brand new thermostats are possible. I've had 2 in the 35 years I've been fooling with cars. One that just wouldn't open, and one that the top "brace" broke the first time it tried to open, so that the moving part had nothing to push against and couldn't open. Never had one on a boat.

Put a thermostat in it. It's cheap enough, and your boat will run better and more efficiently at it's proper temperature. If it's still overheating with a good thermostat, then running without a thermostat is just masking a problem that's gonna come get you when you're 20 miles offshore!

 

[JustJason]

Re: Thermostat problems help!!!!!

2 things.... either splice in some clear vynil line from the water hose that goes from the transom plate to the tstat housing and check for water and air bubbles......
Or... the cheaper route, on a cold engine in the water (not on the muffs) pull the water hose off the tstat housing and fire up the engine for 10-15 seconds and make sure your getting good supply out of that hose... it should be pumping like a garden hose.
Once you verified supply to the engine, then move on to the engine. Don will probably know this off the top of his head and i could look it up if i had your serial### but does somebody know if they used check balls in 88? Something tells me thats a little early but you never know. another thing you can do is check your setup against the diagrams on mercruiserparts.com and check to make sure you have everything routed correctly.

 

[sebas54]

Re: Thermostat problems help!!!!!

Ok, I just finished testing the T-stat and it worked perfectly.

I put it back in the boat and took it for a ride and I over heated again. Why??

When I take the T-stat out it cooled the engine down to 100 degrees.

I just replaced the impeller; could I have messed something up when installing the impeller??


I will take the hose off the T-stat housing tomorrow to varify water flow when the engine is on.


Please, What is the problem with this engine not likeing T-Stat.

I didn't have this problem last season.

When I changed the impeller the old one looked fine.


Did I mess something up.

Please help.


Thanks

 

[Don S]

Re: Thermostat problems help!!!!!

Your problem could be as simple as it's not installed properly.
Can you post some pictures of your thermostat housing and how your stat is installed?

 

[sebas54]

Re: Thermostat problems help!!!!!

Yes, I will do so first thing tomorrow.

Thanks, have a happy and healthy Memorial Day.

 

[sebas54]

Re: Thermostat problems help!!!!!

Okay, Here are the Pictures.



I disconnected the intake hose and water was flowing pretty good. It was spraying but it was flowing pretty steady.


When I have the boat docked, I let it run to operating temp. and it stays where it is supposed to, 150 degrees. I can see the temp rising and then cooling when the t-stat opens. I bring the RPMS to around 3500 and let it stay there and the temp does not rise.

But when driving the boat it will over heat and no water will go to the riserers.
When this happenes I remove the t-stat and the engine runs very cooled


What is going on.


Please help.

 

[Fireman431]

Re: Thermostat problems help!!!!!

You have an obstruction. When the thermostat is open, it is allowing enough water to go by (not under load) to keep it cool. When under load, not enough water is getting by because the engine is working harder and needs more water to stay cool. When you remove the t-stat, there's plenty of water going by, but the engine doesn't get up to proper operating temp. Clean the risers and replace the water pump. If you repaired it with waterbond, all you did was stave off a problem that's going to rear it's ugly head while you're out with the family on a weekend. Repair the engine with the proper parts and you will get rid of the headaches.

 

[Silvertip]

Re: Thermostat problems help!!!!!

Drives one nuts doesn't it Don! But good for business. I don't understand why folks even ask the question if they are going to ignore the advice anyway. I once saw a guy lose an entire brand new exhaust system because he was too lazy or broke to install tail pipe hangers. The wires broke, everything dropped down and he ran over the whole mess. There is an old adage that goes like this: Fix it and pay me a little bit now or ignore it and pay me a whole lot more later.

 

[sebas54]

Re: Thermostat problems help!!!!!

I replaced the water circulator pump today but I didn't take her for a spin.


So, should I take her for a spin and see how it doers under load.



Could the obstruction have been in the water pump???


Thanks for all the advise.


Slivertip, please try and help me not insult me.
I take all the advise and try my best.


This boat is driving me crazy!!


All I want to do is enjoy the summer and go fishing.

Thanks



Also Last seaon I changed the riser and manifolds and I also changed the impeller this spring.