150 Merc heating up

W

wellcraftinmass

New member
I have a 1989 Merc 150 that heats up after about 5 minutes running. I pulled the lower unit and found the past owner had installed a new pump and liner, as he stated he did. The pump tube guide went back in place like it was supposed to when I put it back together. Any ideas why its still getting hot and buzzing??

2nd problemis the tilt/ tim system shot the bed this week, anyone have one for sale? 3 ram, side fill. LMK and thanks
 
Check your thermostats to make sure they are opening. A lot of times they jam shut with salt or just old age. A quick test is to take them out, put them in a saucepan on the stove under water, turn on the stove and watch them... if they don't open by the time the water boils it's time for new ones. If they do open, then do the same test again, but this time put a thermometer in the water and check the temp that they open at. It should be the same or very close to what the engine specs call for.

If they opened, then check all water passages for salt or sand or something that got ingested by the intake and passed up into your engine.

Also, you say that the horn is going off but you don't say anythng about the actual engine temp. Is there a water stream coming out of the engine? (is it pissing?) Is it really hot or is just that the alarm is sounding? What is your temp guage reading? I have a 200 Merc of the same year as yours that had a problem, and it turned out to be a bad heat sensor on the port side of the engine.

If the problem is your t-stats DO NOT be tempted to just run the engine with the t-stats removed. They are there for a reason. Your engine needs a certain temp to help burn off carbon.. you can ruin an engine by running it for a long time with the stats not installed. It's ok to do in order to get back to port, but install new ones at your earliest opportunity.
 
thanks

The water starts out of the tube but then it turns to steam about the same time the engine buzzer goes off. I will check the thermostats today. Thanks again for the info. Now on top of everything else, the oil pump drive shaft appears to have busted the gear, because the motion sensor is buzzing all the time and the oil is not feeding from the upper resevoir. This motor is driving me nuts. Now I mix the oil in the tank. now back to work thanks again. :hide:
 
Sounds like your pump is ok, since the pisser is pissing... (god, where do we get these names from...lol)...Anyways, since you are getting water flow my bet would be that one of your thermostats isn't opening. Remove them from your engine, put the covers back on and then try running your engine again. (Don't worry, you won't do any damage to the engine for that short a run) If it runs cool and the water doesn't turn to steam you've found your problem. If you still get steam then it's a good bet that you have blocked passages or hoses. To narrow it down even further, you can check where the problem is by just putting your hand on the heads of the motor after it heats up. If one side is cool and the other is really hot then the side that is hot is the side with the blockage.
My bet would still be on the stats though until proven different.
 
Thanks guys

I pulled both thermostats and the engine is running cooler, but its hard to tell now because its only running on the hose and muffs in the back yard. But the heads both ran cool the entire time it was running in the back yard. I am hoping that was the problem. Both stats were dirty and I ran the test you had mentioned and they both opened, but seemingly not very far. I am hoping thats the heating problem.

Now the trim problem. I ordered a used trim unit off ebay, basically to get the tilt piston. The tilt piston is leaking from the top packing. I wouldlike to get a complete rebuild kit for all three piston if I could. Does anyone know the best place to get "O" rings or packings for a 1989 Merc 150, 3 ram, side fill T&T unit???? Thanks again.
 
valve

I am going to pull that valve you are talking about and check it. At idle, it doen't seem to heat up, but at full throttle it heats quick, so who knows. All I know is that I want to get it in the water before the end of the season. Thanks again everyone.
 
When I was working on mine I was beatting on the lower unit with a rubber hammer trying to break it loose an could hear sand falling through the inside of the motor, then when I removed the final bolt (aka the reason it wouldn't come off) and the l. u. came off, a bunch of sand came out too.
 
You may need to start a new thread about the tilt problem so the guys will see it.......I know there are several excellent Mercury mechanics on here.
 
poppet valve

I bought everything to replace that poppet valve and thats next on my list. Still no on the water test yet as I have now have to fix the tilt and trim first. And so it goes on.:booty:
 
All better now

I fianally got the 18 fisherman into the water last week and its all better now. I replaced both the thermostats and the poppet valve and the Merc is running like a champ right now. I am actually surprised at how well its performing. Now I have to try a couple of different props on it. I have a 17 inch merc aluminium on it and that one throws it out of the hole and on plane in about 30 feet. Its nice because you can throttle down to nothing and still keep her up on plane, but not good for covering any distance or economy. I also had to put on a brand new trim system, but got a great deal from Action Marine in Holyoke on a new in box unit. So now with a couple of minor items to pick up and down to CT. and the river and sound. Thanks everyone for the info. Have a great day. :clap:
 
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