magnum ll 150 overheat questions

lmuss53

Lieutenant Junior Grade
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Sep 9, 2008
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1,227
Ok I got this 1989 magnum ll 150 from a coworker who is fed up with it ?nd asked me to just get it running and sell it for him. He had overheat alarms a week ago and put a new pump assembly in. When he tried it on the ear muffs it didnt pump right away and he just gave up. He also had a wiring mess and deadbatteries under the hood so I just pulled the 2 batteries along with 2 Perko switches out and wired it to one battery with no switch so I don't have to worry about wiring issues until the motor is running right. I got it running and have a stream coming out the telltale but the right side got noticeably hotterafter a few minutes at idle on my muffs. I pulled the thermostat apart and put the empty shell back in and the right side got cooler but after about 6 or 8 minutes of idle it alarmed. I ordered new stats but they wont get here until Wednesday. I'm thinking I am not getting enough water from the hose right now so I would like to go put the boat in the water and see if it still gets hot. My question is will it hurt to run it a half hour or so with no right side thermostat? The motor is on a winner bassboat and really is a nice powerplant when its working right. Also can anyone think of something else to check? This is my first adventure with a big v6 I'm usually messing with omc twins or maybe a triple. Also I ordered a thermostats kit with 2 stats and 2 gaskets is that all I need to replace the thermostats? And finally please excuse my typing and lack of punctuation I am tapping this out on my wife's kindle since my Pc decide to go in the dumper today.
 

lmuss53

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Re: magnum ll 150 overheat questions

Gonna bump this one time.
 

Chris1956

Supreme Mariner
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Mar 25, 2004
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27,033
Re: magnum ll 150 overheat questions

You might rebuild the poppit valve as well. I would not think it would be an issue to run w/o a thermostat, but monitor the motor temp when you do it.
 

lmuss53

Lieutenant Junior Grade
Joined
Sep 9, 2008
Messages
1,227
Re: magnum ll 150 overheat questions

OK, more info here now. The owner put in a new water pump kit but got no telltale on his muffs he said "I give up, see if you can get this running and sell the !@#$%^ thing."

I put new thermostats in and the motor alarmed intermittently on the muffs in my driveway but had a good telltale, and then didn't alarm at all when I put it in the tank at my friends shop. I let it idle in his tank for about 15 minutes while I helped him with something else and it never made a peep. We ran the rpm up a bit and saw from 5 pounds to 15 pounds of pressure on the water pressure gauge. We figured it was OK and I took it to the launch for a test run.

It idled out of the no wake for about 15 minutes without a peep then right as I was about to go it alarmed something like this Beeeep......Beeeep......Beep...Beep...Beep...Beep...Beep...Beep...about 20 times then BEEEEEEEEEEEEEEEEEEEEEEEEEP STEADY, for about 30 seconds so we turned back. About the time I turned back it quit beeping so I turned for the open water idled along for about a minute then let her rip. Took about a 5 mile run at from 1/3 throttle to wide open without a peep from the beeper, and with 8 to 15 PSI on the pressure gauge every time I looked at it. A we approached the no-wake on the way in and it was coming down off of plane I got about 4 or 5 interupted beeps and then it was quiet all the way back to the dock.

Can someone who understands this warning system and the oil injection system and the relationship between the two help me try to understand what's going on here. I called the owner and he said "Yep, It always did that ever since we had it, we just ran it. If it's peeing and not alarming at idle you fixed it." That may work for him OK and it may be just fine but I can't sell it like this. If it was an OMC I'd be thinking about jerking the tank out, unplumbing the oil pump, disabling the oil side of the alarm and pre-mixing the gas about right now.

Any help is deeply appreciated.
 

lmuss53

Lieutenant Junior Grade
Joined
Sep 9, 2008
Messages
1,227
Re: magnum ll 150 overheat questions

One bump, so the dayshift guys see it.
 
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