1996 OMC 5.0FI (50FAPNCS) Fuel Reservoir/Cooling

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May 2, 2021
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Hi guys, new to this panel and am grateful for any guidance. I have a 1996 OMC 5.0FI (50FAPNCS) engine on which I just installed a Monitor MFH 5057 Fresh Water Cooing System. After being told by the supplier that this was the correct kit, I found that SEVERAL modifications were necessary. The kit's instructions do not account for the water line coming from the underside of the intake manifold to the old thermostat housing. Tech Support for Monitor advised to just connect that line to the thermostat bypass nipple at the front of the intake manifold, which I did.

Question: upon further inspection, I see what appears to be a cooling line coming from the side of the Fuel Reservoir. From what I can see without removing the upper intake, it appears that it attaches to the underside of the upper intake, and then continues into the line I described earlier that went to the old thermostat housing. I believe there is also a line off this leg that runs to the Map sensor? If my observations are correct, would this line from the fuel reservoir have raw water in it from the two larger lines that connect to the reservoir that are obviously raw water fed?

I have searched and searched for information and/or diagrams of the reservoir, but nothing is really clear in this. I obviously don't want to feed raw water through the reservoir and into the intake and then the engine.

Any help is greatly appreciated.
 
Joined
May 2, 2021
Messages
7
Hi guys, new to this panel and am grateful for any guidance. I have a 1996 OMC 5.0FI (50FAPNCS) engine on which I just installed a Monitor MFH 5057 Fresh Water Cooing System. After being told by the supplier that this was the correct kit, I found that SEVERAL modifications were necessary. The kit's instructions do not account for the water line coming from the underside of the intake manifold to the old thermostat housing. Tech Support for Monitor advised to just connect that line to the thermostat bypass nipple at the front of the intake manifold, which I did.

Question: upon further inspection, I see what appears to be a cooling line coming from the side of the Fuel Reservoir. From what I can see without removing the upper intake, it appears that it attaches to the underside of the upper intake, and then continues into the line I described earlier that went to the old thermostat housing. I believe there is also a line off this leg that runs to the Map sensor? If my observations are correct, would this line from the fuel reservoir have raw water in it from the two larger lines that connect to the reservoir that are obviously raw water fed?

I have searched and searched for information and/or diagrams of the reservoir, but nothing is really clear in this. I obviously don't want to feed raw water through the reservoir and into the intake and then the engine.

Any help is greatly appreciated.
Ok guys, sorry for the mistakes in my previous post. Upon reinspection, please disregard my questions about the MAP line. I now see that the line on the side of the reservoir is the same line that I connected to the thermostat bypass nipple at the front of the engine. With THAT knowledge, is there any reason to run that small line from the reservoir to the thermostat bypass? Seems like I should just plug it at the reservoir and at the thermostat bypass nipple and that will close up the loop for the engine cooling system. does this sound correct?
 

Bondo

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67,542
Ayuh,..... Welcome Aboard,...... Is this a brand new motor in a '96 boat,..??
Or is this the original '96 motor that's been raw water cooled all these years,..??

If the latter, yer wastin' yer money on the freshwater coolin',....
 
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May 2, 2021
Messages
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Ayuh,..... Welcome Aboard,...... Is this a brand new motor in a '96 boat,..??
Or is this the original '96 motor that's been raw water cooled all these years,..??

If the latter, yer wastin' yer money on the freshwater coolin',....
Thanks for the response, Bondo. It's actually a 1975 Skipjack 24 Open that was repowered with a 1996 engine and outdrive. There were few hours put on the drive train before the last owner let the boat sit, and eventually let it go to me. I figured I would try to get as much life as I can out of the drive train with the fresh water kit. Either way, the kit is bought and installed. I am just trying to make sure I have the system closed up properly.
 

Scott Danforth

Grumpy old guy who plays with boats
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Jul 23, 2011
Messages
34,487
if the motor saw any salt water prior, you wasted your money on the raw water kit.

the only time you can put a HX on a motor is a fresh water motor that you mechanically clean the sediment out of.

a salt water motor has rust scale in the water jackets that flakes off. these flakes of rust will plug your heat exchanger.
 
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Thank you Mr Danforth, but that horse is already out of the barn. Just hoping for some advice on the fuel reservoir, deleting that line, and closing up the engine cooling system.
 

Scott Danforth

Grumpy old guy who plays with boats
Joined
Jul 23, 2011
Messages
34,487
you need to keep the fuel reservoir cool. otherwise you vapor lock by fuel boiling in the reservoir. hence the water-cooled nature of the reservoir.

you will need to be creative in plumbing it to the raw water side. suggest between the raw water pump and the discharge on the exhaust elbows
 
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you need to keep the fuel reservoir cool. otherwise you vapor lock by fuel boiling in the reservoir. hence the water-cooled nature of the reservoir.

you will need to be creative in plumbing it to the raw water side. suggest between the raw water pump and the discharge on the exhaust elbows
Thank you, Sir. Exactly the information I was seeking. I do have the large (1.25 inch or so?) lines on the aft wall of the reservoir. Are those both supply lines to the reservoir? Is the small line (3/8 inch or so?) off the starboard side of the reservoir that ran to the thermostat housing used as the exit line to remove the raw water supplied by the two larger lines?
 
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you need to keep the fuel reservoir cool. otherwise you vapor lock by fuel boiling in the reservoir. hence the water-cooled nature of the reservoir.

you will need to be creative in plumbing it to the raw water side. suggest between the raw water pump and the discharge on the exhaust elbows
Mr. Danforth, thank you again for your response. I was able to make a clean tee into a raw water line feeding the exhaust. I feel much better about how it is set up now.

I really appreciate the information you provided.
 

Scott Danforth

Grumpy old guy who plays with boats
Joined
Jul 23, 2011
Messages
34,487
Thank you, Sir. Exactly the information I was seeking. I do have the large (1.25 inch or so?) lines on the aft wall of the reservoir. Are those both supply lines to the reservoir? Is the small line (3/8 inch or so?) off the starboard side of the reservoir that ran to the thermostat housing used as the exit line to remove the raw water supplied by the two larger lines?
you should have a 1.25" inlet to the reservoir. the 3/8" line may be an overflow or a vent line. what does Monitor say?
 
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you should have a 1.25" inlet to the reservoir. the 3/8" line may be an overflow or a vent line. what does Monitor say?
Meh, Monitor's Tech Assistance admitted that he wasn't familiar with the Ford engine kit, as he has only dealt with Chevy engines. He recommended I connect the line in question to the thermostat bypass nipple, which I did, but then realized later upon final inspection that this was really wrong, and would likely mix raw and fresh water. That's what prompted this thread.

Like I said in my last reply, I was able to tee into the raw supply for the exhaust. So, now that small line is run just like before, only it goes into the exhaust supply line instead of the thermostat housing. essentially it is the same, just 2 inches further down the line than it was before. Even retained the anti-siphon ball valve!

I believe I'm all good now on this front. It's the other 1,000 things to do on this project that haunt me :)
 
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