1988 Evinrude 90 Overheating

[Outrage 19]

It seems I have an overheating problem. I started my motor on the hose and after about 5 minutes I noticed there wasn?t any water coming from the tell tail so I shut her down and pulled the lower unit to replaced the water pump. While I had the lower unit off I wanted to confirm I didn?t have any blocked passages so I connected a hose to the water pick up tube, turned on the water and without starting the motor I had water streaming from the Tell Tale. To make sure I had water circulating through the heads I disconnected the two hoses going to the thermostat housing and sure enough I had water coming out there too. I replaced the water pump and reinstalled the lower unit. After about 5 minutes of running the motor on the hose the alarm starts sounding. I shut her down and did the 3 second test, sure enough she?s hot (at least I know my temp sensors are good).

Three things to note;
1) while the motor was running, I did have water coming out of the prop hub
2) I did not have water coming out of the 2 holes at the top of the mid section
3) My idle for some reason surges between 1000 and 1300 RPM.

OK sorry for the long story now on to the questions.
1) What?s causing the overheating; Thermostats, Lean fuel mixture, Blockage after the Thermostats?
2) Aren?t I suppose to get a spit of water out of the holes at the top of the mid section?
3) Could dirty carbs be causing the high surging idle and the overheating?

As always I appreciate any input and advise thanks in advance

Outrage 19

 

[Bilge Monkey]

Re: 1988 Evinrude 90 Overheating

I would pull your thermostats out, and with the covers off. Run your motor on the hose and see if you get water at the thermostats

 

[Outrage 19]

Re: 1988 Evinrude 90 Overheating

The thermostats are at the end of the circuit according to the Johnson / Evinrude Manual so when I pulled the 2 hoses that go to the thermostat housing that was in inlet side of the thermostats.

 

[ezeke]

Re: 1988 Evinrude 90 Overheating

Why do you think that the water pump is working properly?

 

[Outrage 19]

Re: 1988 Evinrude 90 Overheating

Hay Ezeke how's it going. With the motor shut off I don't get any thing out of the Tell Tail or the Prop Hub.

 

[ezeke]

Re: 1988 Evinrude 90 Overheating

Everything you wrote says the water pump is not right. Check the impeller and the key again. Also make sure the opening where the water tube enters the water pump is clear; the grommets get shoved down in there.

When you put the gearcase back on, make sure that you have that big rubber exhaust housing seal in place, even if you have to tape it down.​

 

[Outrage 19]

Re: 1988 Evinrude 90 Overheating

Will do Ezeke you haven?t steered me wrong yet. I?ll pull the lower unit again and make sure all is good and fitted, seated, and sealed.

 

[Marc III]

Re: 1988 Evinrude 90 Overheating

I second that diagnosis Ezeke. I learned from others on the board to go ahead and install the impeller and key on the shaft and then install the cup turning the driveshaft clockwise. A little grease or soap (and three hands) helps with chunky OMC impellers.

 

[Outrage 19]

Re: 1988 Evinrude 90 Overheating

Hi Marc III that's the way I learned how to do it when I worked at an Evinrude dealer in 83 & 84.

 

[emdsapmgr]

Re: 1988 Evinrude 90 Overheating

Another possibility. The waterflow schematic shows the impeller directly feeds the block first. The heated block water exits the block through the thermostat housing. The telltale may function properly, yet the engine could overheat if there is a problem in the housing. Any restriction in that housing can cause the block to overheat. The tests you did checked everything except the thermostat/hsg. There could be two issues in the housing: 1. the thermostats are bad. 2. The two very small holes in the thermostat valve body may be plugged. If these two small holes get plugged (not unusual), the hot block water will not get to the back of the thermostats to permit them to open. Probably time to open up the thermostat housing and have a look. Also, check the pressure relief valves to make sure they will function properly at high speeds. When the thermostat/housing is functioning properly, you should see water coming out of the exhaust relief holes.

 

[Walker]

Re: 1988 Evinrude 90 Overheating

Always test the waterpump with the motor in a test tank or barrel.

 

[johnson1989]

Re: 1988 Evinrude 90 Overheating

I had similar issues. Mine turned out to be the water deflectors had swelled up from a previous overheat or age. This thread might help you. I had replaced water pump and stats and still had over heat issue on the left bank.

http://www.marineengine.com/discus/messages/12478/71197.shtml

 

[Outrage 19]

Re: 1988 Evinrude 90 Overheating

Well I tried every thing suggested but couldn?t get the thing to run cool. I pulled the lower unit and made sure everything their was good. I pulled the heads and found the diverters in the wrong place (they were on the wrong side of the bumps that hold them in place) put them back where they belonged. I tried back flushing the system by pulling the lower unit and connecting the hose to the outlet spout on the heads. I didn?t get much junk out so I decided to pull the Regulator / Rectifier, which needed to be replaced any way (I?ve had the replacement sitting on the work bench for a month now). With the Reg / Rec off and the hose connected to the heads I flushed again (every thing looked good from that view) so I put it all back together with the replacement Reg / Rec and presto she run cool. So I?m figuring the Reg / Rec was getting so hot the water couldn?t pull enough heat from the cylinder walls and heads.

Well now that she?s running cool I take her out for a run and I find a new problem that I?ll start a new post for.

Thanks everyone for your suggestions