I just bought this boat has a 93 70hp yammie and got it out to test. It took 20 minutes at 2100 rpms to get the overheat buzzer to go off but it only takes 3-5 minutes to reset and I can go again if I want. has strong pee hole. I first ran it in a barrel of Salt Away about 6 or 8 times. no help. I took the pressure tube off the corroded gauge and there is not pressure. Took t-stat cover off and no t-stat so I replace it with a new one nad got a little pressure back from tube. just got out and it took a little longer but overheated. He said he just got the water pump changed (dont believe that) but its pissing good. Any suggestion Before I change the water pump and when I do should I change the whole thing with the kit?
How much water should come out of the presssure gauge tube?
When I replace the gauge what should the water pressure(s) be?
I am afraid the ports are scale over with salt deposits but dont want to jump to any conculsions.
update:
Dropped the lower unit and as I suspected the water pump is new. Which leads me to thing the previous owner had the saame problem and took the t-stat out ot correct it.
Any advice on unclogging the ports in the head short of taking it off. I tried 2 bolts and would probably break those off.
Thanks
Sounds like you may have to pull the head. I heat them up first and carefully see if they break loose. If not I spray them with PB Blaster and let it soak in before heating and trying again.
Just by reading other peoples post I kind of figured it out. I have had the Salt Away in there for 2 days and I am going to drain it tomorrow. I rigged up a funnel and a tube to the Pressure gauge tube so it would feed the Salt Away right in to the Head. I am not real confident I will have much luck.
I am going to put the new water pump on and test it one more time to see if I get any better results. I got a temp gun from a friend.
How long can I heat the bolts up without hurting anything?
Best quote of the day was from a mechanic at the marina " you can break the bolts off for free or I can charge you to break them off for you "
Check to make sure when he put the impeller and set the ends backwards, if you have to pull the heads spray the bolts with a product called Aero Kroil, and let sit over nite, you may even want to heat the bolts up after spraying them, let them cool down then spray again then let sit overnight. Water pressure should be between 15 and 20psi at around 4000rpm, but it still may over heat if there is a lot of corrision in the water jackets in the cylinder heads and head covers
Stop!!!!!!!!!!!!!!!!!!!!!! It may only be the sensor. I have a 60 hp Yamaha that I changed the Impeller, thermostat and finally found the sensor was sounding 30 degrees lower than it should be. Get you a manual and it will explain how to test the sensor. I also installed a temp gauge in case I had not cured the problem. I found then that I had fixed the problem. Another thing I found with my boat is that the owner before me installed a high speed pick-up for the live well and creates disturbed water before getting to the motor and the result is more air in the water going through the motor that really should helping the motor run hotter that normal. Good luck but I would try everything else before taking the power head apart, that in itself could create more problems that you have now. Turtleman
I am just getting it back together and I am going to go out and test it to see if the new pump helped. I have a thermal gun that I am going to take heat readings with and see what they say. I am trying everything before I crack the head open. I have been running Salt Away thru the engine all week with a funnel system I hooked up.
I also put the piece from the water pump in the Salt Away to see how aggressive the Salt Away is. It didnt do to good of a job cleaning up that plate.
I will give you and up date on what I find out on the problem
To be on the safe side I have been hitting the bolts on the head with PB blaster all week in case this is my last option.
I dont have a manual....does anyone have the torque ratings for he head bolts on a 1993 70hp Yamaha? It would be apprieated!
IS 12 out of 14 a good ratio.....maybe for you guys but not for me. I broke the 2 bolts at the bottom of the head and tried to use a right angle drill to get them out and messsed that up. So my powerhead is completely off and on the bench.
But on the good side I found the problem. The water column is 90% blocked.
I have 2 questions.
If I have to use a Spring will that hold and or can I have someone weld the hold and retap it? If anyone has some input it would be appreciated.
Could my exhaust manifold be blocked also?
Oh yeah I forgot I broke a small bit inside one bolt to make my day!
I had to have a Aircraft machine shop drill the broken bit out and now am waiting for the welder to weld the hole soild again so the Machinist can retap the hole.
The head was completely blocked and i can see why it overheated.
Well all in all it cost me about $200.00 to repair this motor which most people would have gave up and parted out. The motor runs strong and upped my compression to 125 psi.
I had a great machinist tell me that he could have fixed the head buy using EDM ( electrical discharge machining) That will blow a perfect size hole in any material even if you break a drill bit or tap in the screw.
It probably would of saved me a couple of bucks if I would have went striaght to him instead of the aircraft machinist first.
SO Dont throw out those old overheading motors because you break off a couple of head bolts!
Hi Everyone,
I wish I wasn't here posting but I am. I just changed the shift shafts on my 2 engines. That was a project, but went smooth.
My Starboard engine all of a sudden, is sounding the alarm horn. I changed both water pumps & thermostats. I checked the engine temps with a temp gun. One is 132 the other is 213. I had no problem, when they were in the water. I rechecked the water pump and it's fine. There is also a good stream of water coming out of the small hose. I saw the buildup on heads pictured on the thread, but can't believe, I would have that problem. I know Rodbolt is the expert on this stuff. So I hope someone can help me. Thanks in advance for the advice. Bob
Re: Yamaha 200hp Buzzer for overheating ( Added Info)!!!!
I wish I wasn't here posting but I am. I just changed the shift shafts on my 2 engines. That was a project, but went smooth.
My Starboard engine all of a sudden, is sounding the alarm horn. I changed both water pumps & thermostats. I checked the engine temps with a temp gun. One is 132 the other is 213. Oil tanks are both full. I had no problem, when they were in the water. I rechecked the water pump, and it's fine.
I also pulled out the pressure valve that was a little corroded, but not that bad. I'm not sure what it's function is? There is also a good stream of water coming out of the small hose. I saw the buildup on heads pictured on the thread, but can't believe, I would have that problem. I know Rodbolt is the expert on this stuff. So I hope someone can help me. Thanks in advance, for the advice. Bob
93 Yamaha 70hp Buzzer for overheating
It may only be the sensor. I have a 60 hp Yamaha that I changed the Impeller, thermostat and finally found the sensor was sounding 30 degrees lower 
than it should be. Get you a manual and it will explain how to test the sensor. I also installed a temp gauge in case I had not cured the problem. I found then that I had fixed the problem.
Another thing I found with my boat is that the owner before me installed a high speed pick-up for the live well and creates disturbed water before getting to the motor and the result is more air in the water going through the motor that really should helping the motor run hotter that normal. Good luck but I would try everything else before taking the power head apart, that in itself could create more problems that you have now. Turtleman
Re: 93 Yamaha 70hp Buzzer for overheating
Linear Mode
