Johnson 90 VRO Overheating, IM LOST!!

[dethloff04]

Hello Everyone!I purchased a used boat which came with a 86 johnson 90 vro.Motor cranks right up but i have an overheating problem.So far i have:

1.)removed the thermostat housing(sand was in the housing, which i throughly cleaned and replaced with two new t-stats.
2.)I then cranked the motor up without the hoses connected to the t-stat housing to see if im getting flow through the cylinders=water comes out of each side
3.)didnt check impeller, only because the pisser is peeing good and there is water going through the water passages through each side

With the t-stat housing replaced the left side cyclinders dont overheat but the right side does.I checked both of the new t stats to make sure there opening in a pot of water on the stove.I steems like the water flow is getting blocked somewhere, but i dont know where because im getting water through the pisser, through to each side before the t stat housing, but the right side seems to become more pressurized after water fills the tstat housing and wherever else.

ANY ADVICE WOULD BE GREATLTY APPRECIATED~!!!

 

[emdsapmgr]

Re: Johnson 90 VRO Overheating, IM LOST!!

The thermostat housing valve body has two extremely small holes cast into it. Each hole feeds water to the backside of the thermostat which causes heated water to open the thermostat. If these holes get plugged (happens frequently), then you will get an oveheat at low rpm-regardless of anything else you do. Check those holes and make sure they are clear.

 

[dethloff04]

Re: Johnson 90 VRO Overheating, IM LOST!!

thermostat housing valve body?What piece are we talking about, the acutal thermostat with little holes in it, or the t stat housing which holds the t stats?just wondering where to find these holes to check them.From what ive read it could also be the water deflectors?can those cuase over heating a idle as well?please let me know. thanks

 

[emdsapmgr]

Re: Johnson 90 VRO Overheating, IM LOST!!

You will need to take the thermostat housing apart again. The part called the valve body is sandwiched between the outer thermostat housing and the exhaust housing. Has the two large holes for the stats, and two extremely small pinholes. It looks like a piece of hard plastic.

 

[johnson1989]

Re: Johnson 90 VRO Overheating, IM LOST!!

You have either a water pump, thermostat or Water Deflector Issue


Here is a simlar thread.. I once had a simlar issue.

Here is Joe Reeves Definition, it sounds like this may be your issue. You will need to remove the head, clean passages, and replace deflectors. Deflectors are #12 in picture

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

(Water Deflectors)
(J. Reeves)

Water deflectors are actually lengths of 3/8" outside diameter rubber hose, installed between the top cylinder and any cylinder beneath it, and also between the bottom cylinder and the block. The purpose of the deflectors is to have the water follow a deffinite path around the cylinder walls. Unfortunately the deflectors between the cylinders will at times swell sideways due to either a previous bad overheating problem, or simply due to age and salt corrosion. This causes a water flow restriction which usually allows the water to cool sufficently at low rpms but not at the higher rpms.

This hose material can be purchased reasonably at any automotive parts type store if you care to make your own, or you can purchase individual deflectors at any Evinrude/Johnson dealership at a somewhat higher cost.

Removing and installing them can be a hassle at times, but not always. I use a sharply pointed scribe with about 1/4" of the tip bent at a right angle whereas I can reach in, jab the tip sideways into the rubber, then yank it out. It's necessary to clean the seating surfaces where the ruber contacts the block with a small rat tail file to eliminate salt deposits etc. When installing the new rubber deflector, coat the deflector and the metal surfaces with WD40 which will act as lubrication to allow it to go in as easily as possible.

Make sure that you insert something into that deflector area before cutting and installing the deflectors if you make your own so that you will be certain that they are the right length and also that they will be seated properly. Usually a very small amount will be left extending about the block sealing area..... simply cut the excess off with a single edge razor blade.

 

[dethloff04]

Re: Johnson 90 VRO Overheating, IM LOST!!

im gonna go for the water deflectors but they dont come in till next week...Ill keep everyone updated!Thanks

 

[johnson1989]

Re: Johnson 90 VRO Overheating, IM LOST!!

THey are just a simple peice of tubing you could get from any hardware store. In the mean time might as well pop the head off and see if they are swelled up. I replaced the head gasket also when I replaced so I made sure to keep the compression up.

 

[dethloff04]

Re: Johnson 90 VRO Overheating, IM LOST!!

i ordered new head gaskets too; thats why i went ahead and got the deflectors there too.

 

[Outrage 19]

Re: Johnson 90 VRO Overheating, IM LOST!!

Hi dethloff04

I just went through troubleshooting the same symptoms as you with my 1988 90 VRO (over heat alarm goes off left side gets hot but right side gets real hot). Have you checked your Regulator / Rectifier? If you have the one that mounts on top of the block it gets very hot when it goes bad and it gets cooled by the water from the pump before the water goes to the cylinders. If your diverters check ok this is something else to look at.

 

[OBJ]

Re: Johnson 90 VRO Overheating, IM LOST!!

I hope your problems get resolved by the deflectors deth but I would also check those holes in the t-stat valve body as emd posted. I've opened mine up to 1/8th inch so they don't plug so easy.

Good Luck!