engine overheats with thermostats

[pjb]

I run twin 1993 Evinrude 225's , the port engine will not **** at any RPM unless both thermostats are removed. Have tried several newish thermostats and it makes no difference. At idle with t'stats in, the engine does not over heat even though there is no flow at the telltale but at 4000 RPM it overheats in 2 or 3 minutes . Take out both thermostats and there is no overheat at high RPM either but the tachometer goes beserk at high speeds reading correctly then nil then 1/2 what it should in a constantly changing pattern yet the temperature guage reads normal. Could the voltage regulator be overheating even though temp guage shows all is normal - both side of the block remain just warm to the touch or is this an unrelated non cooling problem with the voltage regulator which is 6 months old and allways seems to go nuts in an overheat situation . Could toe in/toe out incorrectly set be causing this as this is the only adjustment done before this started but no cavitation audible.<br />Any thoughts appreciated

 

[rodbolt]

Re: engine overheats with thermostats

hello<br /> if you still have the t-stats that screw into a diaphram dont run it with them out. that also is part of the pressure relief system. when was the last complete water pump kit installed? not just an impeller.sounds like you dont have enough water pressure to fill the block.<br /> good luck and keep posting

 

[pjb]

Re: engine overheats with thermostats

Rodbolt, the whole pump was replaced 1 year ago and a new impellar 2 weeks ago, the old one was good but I had the pump housing open so changed it snyway. I do have the diaphram type. With tstats out engine stays cool at all rpms but tach acts up after a while, could this be the result of a hot voltage regulator. Friend says possibly water tube from pump all the way to power head has a leak so pressure is weak. Probably a big job to check that

 

[Don CHICHO]

Re: engine overheats with thermostats

PAPAS TOY:<br /><br />CALL MR. GILBERTO HENRY. HE WAS WORK AT NOVEY<br />(OMC DEALER-JOHNSON-). GOOD GUY . KNOW YOUR PROBLEM!!!!.<br /><br />CALL HIM: 650-0175<br /><br />TELL HIM: REGARDS FROM "DON CHICHO"

 

[Dhadley]

Re: engine overheats with thermostats

Is this the same problem / motor but a new thread?

 

[seahorse5]

Re: engine overheats with thermostats

The whole engine block and cooling system was changed for 1993. There is a blowoff valve on the back of the cylinderblock that should be removed and the hole checked for debris buildup. Also install a 1997 or later blow off valve tip, or drill a 1/8" hole in the center of the plastic tip to bleed out the air. That will help cool the regulator more evenly.<br /><br />I don't understand why the motor won't come out the tell tale. The "pisser" at the back of the motor is connected directly to the water passageway going to the block and should work all the time as long as it isn't plugged up with sand or such. Unscrew it and look inside the cavity. <br /><br />On 1993 and later V6 motors with the "split line" gearcase have to use the 5001595 water pump kit. Older motors use a 5001594 kit. They look similar but if interchanged, a '93 and later motor will overheat at high speed.

 

[Dhadley]

Re: engine overheats with thermostats

If this is the same motor, I believe someone has put a 1992 & older powerhead on a 1993 midsection. I been trying to find out if it actually has 2 indicators. If so one needs to be plugged. From the other thread it looks like this motor has always done this since he owned it.

 

[pjb]

Re: engine overheats with thermostats

Don Chico, I know Henry, he now works for central marino as Novey have given up the OMC dealership. <br /><br />Dhadley, this post is connected with the other one, yesterday we changed the whole leg so it now a very new leg connected to a 92 or older powerhead. I never new p'head was not a 93 as I was working with model# on the power tilt /transom section. We found the inside of the casing where it connects to the powerhead had severe corrosion and even "holes" so it would have been impossible to build much water pressure. we also pulled off the cylinder heads and it was amazing how much salt had built up in what I would describe as cylinder water jackets. Today we are going to run it hard but even in the tank last night is was pissing like a horse!!<br /><br />Seahorse thanks for your input but I now believe my powerhead is a 92 or older - so will have to change my engine description in future.

 

[seahorse5]

Re: engine overheats with thermostats

It sounds like you have a "pieces-parts" engine. That can make troubleshooting difficult at times.<br /><br />Do the thermostats on your motor have a black rubber diaphragm where a plastic thermostat body screws in to? Are there water lines from the thermostat area to a valve on the throttle lever?<br /><br />A '93 midsection has a different water flow than a '92 and earlier, that is why the different water pumps are needed.<br /><br />Keep us posted, and good luck.<br /><br />Where in Panama are you located?

 

[Don CHICHO]

Re: engine overheats with thermostats

PAPAS TOY.<br />O.K. YOU KNOW HENRY!!!. GOOD!!!!<br />WHAT'S ABOUT : PERCHA, BROCE OR IVAN LEE ???<br /><br /><br />DON CHICHO

 

[pjb]

Re: engine overheats with thermostats

Don Chico, Percha is doing well, Broce lost a leg in a car accident and is now in a wheel chair and Ivan Lee died about a year ago, his son who is called Ivan as well is also a mechanic and has been helping me with this problem.<br />Seahorse I have the power head with the valve on the the throttle and black tstats with the diaphram. When I next change the pump should I be asking for apump that matches the leg or the power head? Also if you have time, tell me more about how I could improve the cooling of the V.R. and where exactly to drill the hole. Is it a one way valve that is inserted etc

 

[seahorse5]

Re: engine overheats with thermostats

Since you have a '92 or earlier engine block, the "blow off" valve and drilling out the plastic valve tip does not apply. That was only for '93 and later engines.<br /><br />Make sure you have the complete #5001595 factory water pump kit installed.<br /><br />Good luck

 

[pjb]

Re: engine overheats with thermostats

Seahorse, I just got back from a 100 mile offshore run (Las Perlas Islands) and she ran perfectly. I live in the city. Water here close to shore is pretty muddy hence the build up and corrosion problems in the cooling systems. The help I got from all posters was invaluable and I learned quite a bit from the experience. Begining to realise my engines are on borrowed time, next ones will be a pair of the big carburreted Yamahas - you definitely dont want anything sophisticated down here like 4 strokes, HPDI's or even EFI's.<br />All the best .<br /><br />Peter