1987 120 looper cooling system

[mrfreon]

Hi everyone, this is my first post so go easy on me. I've just got a Shetland 610 with an Evinrude 120VRO looper which has seemingly been butchered a little. Apart from the VRO pump missing, the thermostats have been removed and discarded with the diaphragms cut out to leave the gasket portion. Now I am a mechanic but have had trouble working out the cooling system on this motor. After reading quite a few posts on this site I now have an idea how it works, I think. Without having any thermostats to examine I think it is something like this: At idle, pressure is put on to the diaphragm from the control valve to close the port to the head seating the thermostat, water flow is then controlled by the thermostat from the block to the head, as the throttle is increased towards 1/2 way point the pressure on the diaphragm from the control valve is reduced allowing the water pressure to unseat the thermostat and give full flow from block to head, this would explain the lower temperature at high revs with no restriction to flow, assuming water pressure is up to scratch. How does this sound so far?? If this is correct then with the mod to 1993 spec, the new spring is what controls the temperature at lower revs so it should be possible, if wanted, to adjust the spring pressure (cutting a coil off) and fine tune it to any particular engine/running condition, just thinking out of the box here for a moment. Does this sound correct? because I can't see any other way. Thanks for taking the time to read my post.

 

[lexer440]

Re: 1987 120 looper cooling system

I am not sure if the 87 had fast start, system advances timing for cold starting when temp is below 96f and/or 1100rpm. thought i would mention it as it may have some impact since at idle or low speed faststart may never disconnect. i do know that the temp is important and the v4's will not run well if not up to temp.

 

[j_k_bisson]

Re: 1987 120 looper cooling system

Yep you have describe the system and how it works correctly. I have converted over to the non water control valve. It works great other than you do need to trim a 1/4" off the springs in order to tune the timing when the t-stats unseat. Mine came in at 1.75 and I trimed them down to 1.5 I think. If you check out my 225 evinrude rebuild thread you will find what the actual numbers where.

Hope this helps....

 

[mrfreon]

Re: 1987 120 looper cooling system

Thanks for the reply, I will check out your thread as suggested. I have also received my service manual so if anyone needs any info give me a shout.

 

[Haffiman]

Re: 1987 120 looper cooling system

There are advantages and disadvantages with both systems.
The original manual valve secures full flow through the engine immediately if the throttle is 'hammered' down during water skiing etc. This reduces the risk of a temp increase peak. Further it gives a bigger chance of even flow through both banks and more even temp.
The disadvantage might be that it needs a bit more careful adjustments depending on load and prop selection to get the transition properly.

The spring system is all automatic, and works well as long as the springs are synchronized in tension. It may however as impeller starts loosing pressure, require a higher rpm (read load) before it starts to open, with the risk of temp peaks.

 

[j_k_bisson]

Re: 1987 120 looper cooling system

Yes I would agree with you about the advantages and disadvantages of each system. But with any system maintence is a must. The spring system will require a new impeller as per the maintence cycle listed by the manufacture, like every 2 years max time span. I sure some people will contest this b y saying they run the impeller alot longer than that. But in my opinion they are tempting fate. I change mine every year reguardless of how many hours I have on the motor.

It's alot cheaper then a new motor or a rebuild.

 

[mrfreon]

Re: 1987 120 looper cooling system

Hi Guys, right where to start? 1. I've had most of the outboard in bits, and parts were a real mess but now it's all back together. Problem is hoses for the cooling system, mine had the original throttle control valve for the thermostats, well sort of, they had removed thermostats and cut the diaphrams and the hoses from the covers then went back to the control valve where there were two other hoses connected, one small and one larger which both went to the tell tale outlet. Now I've been through the manual but can't find anything on where the hoses should be routed or come from. There is one hose that comes from the upper part of engine at front and is connected to the plastic elbow on the exhaust housing, although in the book it looks like that may be the one for the tell tale, but I still can't see any other that should probably have connected to the control valve, I assume the valve must have had a pressure feed from somewhere, but where? I want to fit a pressure guage, so if the elbow on the exhaust housing is a feed I could use that, job done. 2. I also saw the post that said you needed to take 1/4 inch off the thermostat springs, so I decided to use the old covers a spacers and faced them off on the lathe to suit, once I get the thing running I will be able to check operation and resize if necessary, hope it works how intended. 3. On the electrical side, near the main 8/10 way plug that goes to the remote control, at the engine end there is an orange lead that comes out of the loom just before the plug, where does that go, it's just swinging free, again the book shows it in the diagram but I can't see where it goes, it was already disconnected when I got the motor. I know some of this will be evident when eventually running but not quite at that stage yet, but nearly lol. Any help please? Thanks for reading