Project Swap..93 3.0LX Mercruiser swap to a 86 Mercruiser 140 (part 2)

[buckz6319]

Good splines:



Bad Splines:

Rich, here is a pic of my coupler splines...I see that it matches your Bad Splines photos. I think I will use the coupler off the 93, provided the flywheel has the 3 threaded holes for mounting.  the splines look good on that one. If I can't use the 93 coupler, then I have to go another route, some new ones cost 200.00 and up

[Rich_V174SS]

That coupler looks like a failure waiting to happen. I've seen the splines strip out clean when they get that worn.

The coupler for my 3.7 liter engine is almost $400 new. I've found used ones on ebay that were in practically new condition for under $100.

[buckz6319]

That coupler looks like a failure waiting to happen. I've seen the splines strip out clean when they get that worn.

The coupler for my 3.7 liter engine is almost $400 new. I've found used ones on ebay that were in practically new condition for under $100.

yep!, I believe your correct. I will see if my 93 coupler will work, if not I will search for this older type

[buckz6319]

Gosh! the humidity is awful here...wish I had an air conditioned  garage to work in:)

[buckz6319]

update...

I thought I would get the Merc ready for the cooling jacket pressure test tomorrow. I removed the t-stat housing, so I could remove the thermostat, and I didn't find a thermostat to remove. It makes me wonder a little.

I guess that the manifold, and riser was bad enough ( I posted pics of the riser and manifold earlier in Reply #25) , that removing the thermostat would allow the engine to run cooler, so that is why she didn't get hot running.

I hope that my pressure test tomorrow goes better than it did on the 93 3.0


ready to pressure test

[ChfBrianB]

removing the thermostat would allow the engine to run cooler, so that is why she didn't get hot running.

I've heard of this being done from time to time.  I had a problem with my CVX-20 / 460BB spiking in temperature when I would come down to idle after running at high rpm. What I did was experiment with different size washers in place of the thermostat.  This way, I was getting constant water flow through the cooling system, and could regulate the amount by the inside diameter of the washer opening.  I think that I tried this method because I was having a hard time finding a thermostat with the proper opening pressure rating.  Not to say that it was a good solution, but it was an interesting experiment.  I think that it's pretty common in race motors as well.

b~

[buckz6319]

removing the thermostat would allow the engine to run cooler, so that is why she didn't get hot running.

I've heard of this being done from time to time.  I had a problem with my CVX-20 / 460BB spiking in temperature when I would come down to idle after running at high rpm. What I did was experiment with different size washers in place of the thermostat.  This way, I was getting constant water flow through the cooling system, and could regulate the amount by the inside diameter of the washer opening.  I think that I tried this method because I was having a hard time finding a thermostat with the proper opening pressure rating.  Not to say that it was a good solution, but it was an interesting experiment.  I think that it's pretty common in race motors as well.

b~

I never heard of doing that, however I can understand the theory
thanks for your input

[dorelse]

The only thing pulling the thermostat ever got me, was a guaranteed overheat...its an old 'trick' that doesn't work in most situations...the water needs some restriction to absorb heat and pull it away from the metal...

[Rich_V174SS]

In some cases the thermostat provides direction for the water to flow and without it it's still possible to have an overheat if water isn't taking the right path. In the case of my engine with closed cooling the thermostat has a "foot" around the base of it that closes the bypass port in the thermostat housing as it is opening to exchange hot water for cooler inside the block. Without the foot water circulation around the block will not be as effective, water redirection will not be as intended.

[buckz6319]

so, given the information on the " no thermostat, causing the engine not to get hot when running "

should I concern my self with it at this point? I know she needs one, and I got one, but right now I will pressure test the water jackets with out one...does that sound right lol

I would be more concerned with the manifold and riser being the possible cause of what the po called " an over heat issue one time thing"...

I too have removed plenty of t-start from engines, so they would run cooler than the normal operating temperature, not sure, and can't remember if it did the trick or not...I guess it is debatable.

[75starflight]

Removing the thermostat is also a way to prevent a cracked head, manifold, block, or blown head gasket from leaking.

[Rich_V174SS]

Removing the thermostat is also a way to prevent a cracked head, manifold, block, or blown head gasket from leaking.

How so? never heard that one before. Water pressure inside the block is generated by moving water from the intake pump and by whatever restrictions there are where the water exits the cooling system, like at the riser. So, whether there's a thermostat or not the water pressure in between should be the same. There's still a bypass around the thermostat for free-flowing water.

[75starflight]

Removing the thermostat is also a way to prevent a cracked head, manifold, block, or blown head gasket from leaking.

How so? never heard that one before. Water pressure inside the block is generated by moving water from the intake pump and by whatever restrictions there are where the water exits the cooling system, like at the riser. So, whether there's a thermostat or not the water pressure in between should be the same. There's still a bypass around the thermostat for free-flowing water.

The 140 I rebuilt that is now in Phoenix was that way. I tried running it on the hose after I got it from Joe and never had any water intrusion. Pulled it apart to find no thermostat and a head with three cracks.

On another note I have known a few friends over the years that have had head gaskets go bad in their vehicles and removed the thermostat to release the pressure on the cooling system to stop the leak until they could afford to repair it. And it did work.

[Rich_V174SS]

On another note I have known a few friends over the years that have had head gaskets go bad in their vehicles and removed the thermostat to release the pressure on the cooling system to stop the leak until they could afford to repair it. And it did work.

But in a vehicle (car or truck) it's a closed cooling system so the pressure will increase as the engine gets hot and water/prestone expands and increases the pressure. Without a thermostat in that case the engine will run cold so there won't be as much pressure generated. In closed cooling systems there's also the radiator cap designed to push open to relieve excess pressure at 13 or 14 psi and send the excess to a catch bottle.

[dorelse]

On another note I have known a few friends over the years that have had head gaskets go bad in their vehicles and removed the thermostat to release the pressure on the cooling system to stop the leak until they could afford to repair it. And it did work.

But in a vehicle (car or truck) it's a closed cooling system so the pressure will increase as the engine gets hot and water/prestone expands and increases the pressure. Without a thermostat in that case the engine will run cold so there won't be as much pressure generated. In closed cooling systems there's also the radiator cap designed to push open to relieve excess pressure at 13 or 14 psi and send the excess to a catch bottle.

I've actually found it to be the opposite.  I had a '79 F100, w/302 that I was told before I used it for a towing trip, to pull the thermostat to keep the engine 'cooler'.  So...following that advice, pulled the thermostat, the truck overheated in 75 miles...put the thermostat back in ran just fine, temp never went passed the thermostat's temp setting.

When I asked a trusted engine mechanic I was told that without a thermostat, the coolant runs through the engine so quickly that it never allows thermal transfer into the coolant, so the engine overheats.  It has to have some degree of restriction to slow the coolant down a bit so it can heat up in the engine, and then also cool down in the radiator.

Anyway, that was my real world experience in the old Ford.  I'm not a master engine builder, but I know that my F100 had to have the thermostat in it to keep it from overheating...

[buckz6319]

Well, from my experience working on  vehicle engines throughout the years. I know that without a thermostat, radiator in conjunction with the fan,  fan clutch, or electric fans these days. The fluid in the radiator will not set idle long enough for the fluid in the radiator to be cooled, then released when the t- stat opens, thus cooling the block ect.

I am no professional mechanic tech, just a professional  IWTDIMS ( I Want To Do It Myself ) mechanic

Given what I know, which is vary little compared to the professionals on here, who I respect and admire.
other opinions are appreciated:)

oh..and I am pressure testing the block, after yard work, feeding the dogs, eat some lunch, wait for my wife to get back, rake the dirt in the back yard, makes it look more better lol

[Maclin]

From Rich:   "...the coolant runs through the engine so quickly that it never allows thermal transfer into the coolant, so the engine overheats. "

This is definitely what goes on inside the engine without a thermostat.

[buckz6319]

Well, I'm now pressure testing the block, but trying to get all the air leakage under control. The main air leakage as of now, is that leaking casting plug in the head. The hoses were leaking but I have them under control I think

I am looking for suggestions on stopping the leak temporary for testing, and if the pressure test holds, then I will be satisfied that this engine will be good to keep moving forward on...

btw the pressure doesn't drop on this 86 140, like it did on the 93 3.0. The 93 3.0 pressure test dropped like a rock once that internal crack opened up

[buckz6319]

Well, I thought I would update this thread...

I found a way around that leaking head expansion plug ( aka, Freeze plug) worked perfect!



Now, I was able to pressure test the block:) before I move forward with the project. The Block is holding steady pressure. I put 20 psi in it, and it vary slowly starter to drop down a little to 17.1 psi. I still have a few air leak gremlins that I need to address. I am sure that once the air leakage gremlins are taken care of, I should hold pressure, sorry my gauge is upside down

Rusted temperature sender air leakage gremlin at 20psi

Water pump hose air leakage gremlin at 20 psi. The clamp is tight, but maybe i can crank on it a bit more


and here is a pic of my new tool I got today

[buckz6319]

I forgot to mention that I also got the Delco distributor installed, and seated

Now I will use the 93 3.0 manifold and riser on the 86 140
And keep moving forward