Johnson v4 120 hp Looper Overheat alarm at WOT

[forsete]

Hi!
My V4 120hp looper -89 overheats at starboard side at 4000rpm and above, with the alarm squealing (high temp measured with gun, so the alarm sensor is correct).

- The water pressure at idle is ~15psi, above 4200rpms it raises to 30psi (max what the gauge can show).

- Tried with the old and new thermostat housings (known as the black variant), same story..

- No issues at idle, then the temp is perfect on both sides (~160F).

- Running the engine with just the thermostat plastic housing on stbd side only (no thermostat inside) works, no alarm goes off, but the pressure does not as easily max out the gauge (quite understandable when no thermostat is inside).

- Started the engine without the t-stat cover and the water shoot out at idle about 3 feet. There was water coming through the line to the t-stat cover as well.


What could be the cause? The port side seems perfectly fine.

How important is the condition of the grommet that seal against the thermostat housing in the cylinder head, if it is a bit leaky connection, could it create such issues..?

Many thanks for any ideas!


//Steve the Swede

 

[Joe Reeves]

Re: Johnson v4 120 hp Looper Overheat alarm at WOT

There is a water control valve on the starboard side of the powerhead which is operated by a stainless steel link connected to the vertical throttle/timing advance arm. The purpose of this water control valve is to allow additional water to flow thru the powerhead as the throttle is advanced to the higher rpms.

This valve is easily identified by the mechanical linkage to the vertical throttle arm and also the water hoses connecting it to the starboard thermostat housing. Has someone bypassed it for some unknown and ill advised purpose?

 

[HenryB]

Re: Johnson v4 120 hp Looper Overheat alarm at WOT

Try switching all the housing parts to see what happens. You got all the water pressure you need, but a restriction somewhere.

 

[forsete]

Re: Johnson v4 120 hp Looper Overheat alarm at WOT

There is a water control valve on the starboard side of the powerhead which is operated by a stainless steel link connected to the vertical throttle/timing advance arm. The purpose of this water control valve is to allow additional water to flow thru the powerhead as the throttle is advanced to the higher rpms.

This valve is easily identified by the mechanical linkage to the vertical throttle arm and also the water hoses connecting it to the starboard thermostat housing. Has someone bypassed it for some unknown and ill advised purpose?

Hi, no all the hoses to the valve is in place. Just realized how the system works with the Diaphragm and water pressures on both sides of it, could it be that the T-stat doesnt move away from the hole? called boost cooling or something.. ? At RPMs above 2000 the water to the thermostat covers pressing the t-stats inwards should disappear, I think..?

 

[HenryB]

Re: Johnson v4 120 hp Looper Overheat alarm at WOT

If the thermostat is a small copper thing with a pin sticking out then all the rest is pressure relief stuff. Somewhere around 2500 rpm the relief valve part should open and release a full load of water.

 

[Joe Reeves]

Re: Johnson v4 120 hp Looper Overheat alarm at WOT

Running the engine with just the thermostat plastic housing on stbd side only (no thermostat inside) works, no alarm goes off, but the pressure does not as easily max out the gauge (quite understandable when no thermostat is inside).QUOTE]

In reading that over a few times, that says that the starboard side only overheats when a thermostat is present.

Switch the complete starboard thermostat and plastic housing assembly with the port side assembly. If the problem follows the starboard thermostat assembly to the port side, install new thermostats.

If the starboard side heat sensor still causes the warning horn to sound... replace the heat sensor.

 

[w2much]

Re: Johnson v4 120 hp Looper Overheat alarm at WOT

Also check your spark plugs. You may be running lean on the hot side causing friction and heat at high speed. Check your oil consumption. Perhaps try a run on premix .If OK you have a restriction somewhere.

 

[forsete]

Re: Johnson v4 120 hp Looper Overheat alarm at WOT

Also check your spark plugs. You may be running lean on the hot side causing friction and heat at high speed. Check your oil consumption. Perhaps try a run on premix .If OK you have a restriction somewhere.

I run on premix, VRO is deactivated. The plugs looks all the same. Restriction around the cylinders?

 

[forsete]

Re: Johnson v4 120 hp Looper Overheat alarm at WOT

Running the engine with just the thermostat plastic housing on stbd side only (no thermostat inside) works, no alarm goes off, but the pressure does not as easily max out the gauge (quite understandable when no thermostat is inside).QUOTE]

In reading that over a few times, that says that the starboard side only overheats when a thermostat is present.

Switch the complete starboard thermostat and plastic housing assembly with the port side assembly. If the problem follows the starboard thermostat assembly to the port side, install new thermostats.

If the starboard side heat sensor still causes the warning horn to sound... replace the heat sensor.

The thermostats have been shifted but the overheat issue stay on the stb side.
Since I have a water pressure gauge installed I will look at it when passing 2000 rpms and see if there is any drop in pressure as there should be when the control valve removes the "inwards pressure" on the stats that then should move avay from the inlet to allow the water to get in freely.. I learned about this today and have therefore not looked for that indication... Before I understood that this happened I actually tried to loosen up the spring inside the stats to allow the water to press down the internal t-stat more easily, this mod could actually make the issue worse since I then loose pressure pushing the t-stat housing away from the hole..

 

[HenryB]

Re: Johnson v4 120 hp Looper Overheat alarm at WOT

When you say that the thermostats have been switched are you saying that all the seven or eight parts in the housing were switched, or just the small copper thing called a vernatherm? I don't think you will see any noticeable drop in pressure, but you have a laser gun, watch the port side and note the temperature at 1500 rpm, then again at around 3000rpm, you should see a rapid drop from 150 degrees
to less than 120 degrees. It means that the pressure relief valve has opened on that side. If you do not see that drop on the port side then it is almost certain the relief valve did not open.

 

[Bosunsmate]

Re: Johnson v4 120 hp Looper Overheat alarm at WOT

are there water deflectors in that model ?

 

[Bosunsmate]

Re: Johnson v4 120 hp Looper Overheat alarm at WOT

hows it run at overheat? any splutterings etc?

 

[forsete]

Re: Johnson v4 120 hp Looper Overheat alarm at WOT

When you say that the thermostats have been switched are you saying that all the seven or eight parts in the housing were switched, or just the small copper thing called a vernatherm? I don't think you will see any noticeable drop in pressure, but you have a laser gun, watch the port side and note the temperature at 1500 rpm, then again at around 3000rpm, you should see a rapid drop from 150 degrees
to less than 120 degrees. It means that the pressure relief valve has opened on that side. If you do not see that drop on the port side then it is almost certain the relief valve did not open.

OK, is it ok to do that kind of revs in neutral..? its kind of hard to measure whilst driving..

I meant i switched the whole t-stat assy between the port and stbd side. The thing is also that on the port side there is a lot of other stuff in the way so I can almost only measure the top side of the cylinder side, not much further forward on the side of the head where the pistons runs inside..

 

[forsete]

Re: Johnson v4 120 hp Looper Overheat alarm at WOT

hows it run at overheat? any splutterings etc?

I shut it down immediately, so I cant tell.. But the head is definitely overheating if that is what you question?

are there water deflectors in that model ?

I think not, belive that is found in crossflow engines though..

 

[HenryB]

Re: Johnson v4 120 hp Looper Overheat alarm at WOT

when the temp max's out at idle take her up to 4000 rpm for about 20 seconds. Both banks should be at 120 degrees or less when you throttle down.

Your engine has a feature called S.L.O.W. that will cut out a bank of plugs when you reach critical temp. The experience is scary but your engine will not be harmed. Twice at full throttle I picked up a plastic bag that covered the water intake. I did not hear or see the warnings because my attention was forward and the engine noise obscured the warning horn. The last occurrence was about five years ago. Since then I have removed the heads for inspection and found no evidence of damage to the cylinder walls. The original cross hatch from the hone is still visible and the compression is 140 x 4.

The engine is a 1998 130 looper

 

[Bosunsmate]

Re: Johnson v4 120 hp Looper Overheat alarm at WOT

have you done a compression test?

 

[Bosunsmate]

Re: Johnson v4 120 hp Looper Overheat alarm at WOT

is it a salty ?

 

[Joe Reeves]

Re: Johnson v4 120 hp Looper Overheat alarm at WOT

are there water deflectors in that model ?

No water deflectors on a looper.

 

[Fed]

Re: Johnson v4 120 hp Looper Overheat alarm at WOT

BRP lists water deflectors for that model.

 

[forsete]

Re: Johnson v4 120 hp Looper Overheat alarm at WOT

Running the engine with just the thermostat plastic housing on stbd side only (no thermostat inside) works, no alarm goes off, but the pressure does not as easily max out the gauge (quite understandable when no thermostat is inside).QUOTE]

In reading that over a few times, that says that the starboard side only overheats when a thermostat is present.

Switch the complete starboard thermostat and plastic housing assembly with the port side assembly. If the problem follows the starboard thermostat assembly to the port side, install new thermostats.

If the starboard side heat sensor still causes the warning horn to sound... replace the heat sensor.

There is a water control valve on the starboard side of the powerhead which is operated by a stainless steel link connected to the vertical throttle/timing advance arm. The purpose of this water control valve is to allow additional water to flow thru the powerhead as the throttle is advanced to the higher rpms.

This valve is easily identified by the mechanical linkage to the vertical throttle arm and also the water hoses connecting it to the starboard thermostat housing. Has someone bypassed it for some unknown and ill advised purpose?

I called a OMC service company today and he told me there could be a restriction in the water control valve.. I Could either try and blow it clean with compressed air when throttle is at max or just bypass it by connecting the hose from the adapter plate(?) found on the stb side (got my pressure gauge teed on to that hose) and instead just put it directly to the thermostat cover on stb side.. I thought it sounded a bit strange because then the thermostats would be engaged/pressed against the cooling inlet at all times.. If you are sure about what the valve does, could you please explain it to me because now I feel extremely confused..

In my world it just routes incoming water to the outside of diaphragms at low rpms and then cuts the pressure to those at high rpms and dumps the water to the pisser, and therefore letting the thermostats move away from the inlets due to the (now higher) pressure pushing on the inner side of diaphragms, letting the water pass by freely without having to pass inside the t-stat assy..