Evinrude 120 Overheating

aloharichhaula

Recruit
Joined
Feb 19, 2002
Messages
3
This past Monday my engine overheated twice. The impeller and thermostats were replaced a year ago. The overheating problem only occurs when running at 3,500 rpm or above. I noticed that when I get above 3,000 rpm my water pressure starts dropping. When running below 3,000 the gauge indicates about 7-8 pounds pressure. When I get above 3,000 rpm the pressure drops to 2-3 pounds pressure. The water coming out of the site check hole seems fine at low rpm but seems to drop off at higher rpm.<br /><br />Questions:<br /><br />1. Shouldn't the water pressure gauge show increased pressure rather than decreased pressure at higher rpm?<br /><br />2. Any ideas about the cause of the problem?<br /><br />Thanks
 

Dhadley

Supreme Mariner
Joined
Feb 4, 2001
Messages
16,978
Re: Evinrude 120 Overheating

First of all -- are you sure you have the gage T'd into the motor in the right place? It almost sounds like you have it tied into the overboard line instead of the in coming circuit. Next -- what year is it? The early V4's had a white thermostat that may be contributing to your problem if that's what you have.<br /><br />Let us know. Good luck!
 

aloharichhaula

Recruit
Joined
Feb 19, 2002
Messages
3
Re: Evinrude 120 Overheating

Dhadley, thanks for the reply. The engine is a 1990 and the thermostats are black. The gauge is the original one installed, so I am sure it is tied into the right place. <br /><br />Never had this problem until Monday. Should the pressure increase or remain the same at a higher RPM? Any other thoughts?
 

Dhadley

Supreme Mariner
Joined
Feb 4, 2001
Messages
16,978
Re: Evinrude 120 Overheating

Did the gauge EVER read higher? Please verify where it is tied into the system. The pressure should be much higher than what you are seeing. <br /><br />It almost sounds as if you are blowing by one (or both) head gaskets. If the motor overheated you might want to replace them or at least retorque the head bolts. <br /><br />Let us know where the gauge is reading from.<br /><br />Good luck!
 

jegervais

Chief Petty Officer
Joined
Jan 18, 2002
Messages
646
Re: Evinrude 120 Overheating

Has the boat/motor gotten into any sand or mud lately? Pressure should definately be higher. Maybe you picked up a plastic bag, the blockage of water flow could have damaged the impeller. The only other thought I have is the seal between the waterpump housing and backing plate - if its not sealing now (for whatever reason) the pump may be ventilating itself with exhaust gasses - this might explain the water pressure drop, especially if the w/p gauge is tee'd in correctly.<br /><br />-John
 

aloharichhaula

Recruit
Joined
Feb 19, 2002
Messages
3
Re: Evinrude 120 Overheating

Thanks for the replies. I don't know if the guage ever read higher, really didn't pay attention to it until this problem occurred. I double checked the thermostats today and everything looks clean. I am religious about flushing after each use. The intakes are clean, did not get into any mud, sand, etc.<br /><br />I think I'll have to drop the leg and check out the impeller. It will be a few days before I can do that, so will get back to you. I'll also check and see where the gauge is tied in. <br /><br />Thanks for the replies.
 

Digdug

Petty Officer 3rd Class
Joined
Jan 23, 2002
Messages
77
Re: Evinrude 120 Overheating

Dahley/John from IL. I have a 1994 Evinrude 120hp. The water pressure guage is t'd into the "pee hole" line. Is this incorrect? Pressure at idle is 5-7 psi / 30 psi at WOT (5900 rpm). Thermostats are brown on my motor.
 

steve forsythe

Petty Officer 1st Class
Joined
Nov 7, 2001
Messages
245
Re: Evinrude 120 Overheating

I hear a lot about 'pressure gauges' around here.....I really worry all the time about cooling, overheating, etc. Is a pressure gauge easy to install??? And finally....rate it for me---- 1. "a must have" 2. "nice to have" 3. "just another gauge" 4. "dont bother" Thanks.
 

Dhadley

Supreme Mariner
Joined
Feb 4, 2001
Messages
16,978
Re: Evinrude 120 Overheating

Digdug -- the correct place to read water pressure on a looper is in the incoming circuit. There is a place for a fitting on the lower starboard side of the adaptor housing on the 94 models. Your readings are pretty good and normally if the gauge is reading the exit or tell tale side the readings are much lower. I like the 5900 RPM deal too. Sounds like all is well in your corner of the world. <br /><br />Purse*Snatcher -- The value of gauges must be determined by the operator. Personally, I like the gauge in conjunction with the warning horn. The pressure gauge tells you what is going on NOW at the cooling water source and therefore what WILL happen at the powerhead. A heat gauge tells you what IS happening. A horn tells you what has ALREADY happened and reminds you it's time to shut down. <br /><br />I like your rating system. I watch the water pressure gauge in my boats constantly (especially while using the hydraulic jack plate) so I would rate it as a 1. I guess the frequency that you look at it determines the importance. If you never pay any attention to it I guess it's a 4. And it's probably the easiest to install of all the gauges.<br /><br />Good luck!
 

Digdug

Petty Officer 3rd Class
Joined
Jan 23, 2002
Messages
77
Re: Evinrude 120 Overheating

Dhadley, Yes, things are good here in Dallas. Motor is running well and weather is getting warmer by the day. This is my 7th OMC engine and I think it is my favorite. I am purchasing a jack plate next week to add the finishing touch to my boat/motor combination (hope wife dont read this). <br /><br />Purse*Snatcher - This is my first boat that has a water pressure guage. I dont think I could live without one now. I monitor it constantly (even when cruising at low speed). I am like you (constantly think about "cooling / overheating). It just makes me feel better to look down and see that water pressure is good. It beats the heck out of driving around looking back at the tell-tale!
 
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