B mod cooling

[JohnsonM50]

I recently got an OMC 22 with a Bayer tower & an A-B lower. As I got it, it was made to be force fed by a propwash pickup. I want [at least for now] to use the pump, my question is.. The tower is about H height, the rear tube is about 5/8 ID, the water tube in an H tower being about 5/16, would it be too much of a water column for the water pump to maintain ? I know rear port cooled OMCs are backwards of normal and checked to be sure theres no thermostat. I also found a little sealant blob in it. I wanted to ask about whether I need a tube inside the tube so to speak before starting it again. :eek:

[Tim Chance]

I recently got an OMC 22 with a Bayer tower & an A-B lower. As I got it, it was made to be force fed by a propwash pickup. I want [at least for now] to use the pump, my question is.. The tower is about H height, the rear tube is about 5/8 ID, the water tube in an H tower being about 5/16, would it be too much of a water column for the water pump to maintain ? I know rear port cooled OMCs are backwards of normal and checked to be sure theres no thermostat. I also found a little sealant blob in it. I wanted to ask about whether I need a tube inside the tube so to speak before starting it again. :eek:

What is the make of the lower unit (Gear case, foot, whatever you want to call it). Mercury?, Champion? Konig? Yamato?

[mac19f]

The diameter of the tube has nothing to do with the weight of water causing backpressure on the pump. Only the height matters. On the other hand the larger tube would have less friction loss due to flow and therefore cause an overall lower backpressure on the pump.

[JohnsonM50]

What is the make of the lower unit (Gear case, foot, whatever you want to call it). Mercury?, Champion? Konig? Yamato? Its a Merc long skeg [single inlet hole]

[Mark75H]

Its a Merc long skeg [single inlet hole]

Single hole Merc AB is a water pump unit. Are you sure it has no pump?

[Tim Chance]

You have a Merc lower unit with the guts of the waterpump removed so you are using the speed of the boat to force water through the motor. Unless the crappies are biting somewhere and you want to stop and troll I don't see a reason to have a pump. None of the Pro motors have a waterpump: i.e. Arrens, Rossi, VRP, or Koney. I run a Pro 250 motor with a Rossi gearcase and no pump and a Mod FE motor and a Konig (aka Koney) gearcase and no pump. But if you want to run a Mercury pump unless you are severely restricted the pump should pump enough water to cool the motor. Take a short run and check temperature. Then a longer run and check again.

[JohnsonM50]

Single hole Merc AB is a water pump unit. Are you sure it has no pump?
There is a new impeller, with water not reaching the powerhead I will have to look at it tho. :confused:

[JohnsonM50]

You have a Merc lower unit with the guts of the waterpump removed so you are using the speed of the boat to force water through the motor. Unless the crappies are biting somewhere and you want to stop and troll I don't see a reason to have a pump. None of the Pro motors have a waterpump: i.e. Arrens, Rossi, VRP, or Koney. I run a Pro 250 motor with a Rossi gearcase and no pump and a Mod FE motor and a Konig (aka Koney) gearcase and no pump. But if you want to run a Mercury pump unless you are severely restricted the pump should pump enough water to cool the motor. Take a short run and check temperature. Then a longer run and check again.
Thanks Tim, When Im ready to race itll be easy to switch to force fed.

[mercguy]

There is a new impeller, with water not reaching the powerhead I will have to look at it tho. :confused:

the Merc A/B/C foot should have no problem pumping water up to your powerhead through a Bayer tower and keeping your powerhead plenty cool. I never had a problem keeping my Cmod Merc cool with that setup, although I have now switched over to a Yamato PRO foot with force feed water supply. I really would prefer having a water pump though, as you can run/adjust the motor while it is on the trailer in the water and saves the motor if you have problems getting on plane.......:eek:

[Tim Chance]

I know nothing about Merc gearcases, but I would think if it has as new impeller it should work. Have you tried pulling the gearcase off and blowing air through the system, or using a small pump and pumping water through to see if there are any leaks or any blockage?

[JohnsonM50]

the Merc A/B/C foot should have no problem pumping water up to your powerhead through a Bayer tower and keeping your powerhead plenty cool. I never had a problem keeping my Cmod Merc cool with that setup, although I have now switched over to a Yamato PRO foot with force feed water supply. I really would prefer having a water pump though, as you can run/adjust the motor while it is on the trailer in the water and saves the motor if you have problems getting on plane.......:eek: Thanks Daren, When you got somone on the rope and all ya gotta do is drive fast,, then the fishin motor mentality might slow ya a little but I still prefer a pump. If you have to limp in on a barely runnin motor,, :eek: :o

[JohnsonM50]

I know nothing about Merc gearcases, but I would think if it has as new impeller it should work. Have you tried pulling the gearcase off and blowing air through the system, or using a small pump and pumping water through to see if there are any leaks or any blockage? Yes I removed the powerhead and poured water thru, I pulled a small chunk of silicone out of the powerhead and suspect that, just wanted to be sure I wasnt shov-lin it against the tide with the 5/8 ID tube. Im also going to remove the cone nut and check the pump.. then re-try Thanks. :cool:

[fbref5269]

make sure the water pump is in correctly. if you're using it there is a certain way the pump has to be in the unit. if you look at the pump housing as it would be installed in the foot there is a 'bump' by one of the holes in the housing. that hole shoud be by the exit hole by the tube going to the block.

frank

[JohnsonM50]

I took the cone etc. off and the pump looks OK. Ill run it again when I get a chance to set up the custom-made [from junk] motor jockey with barrel-o-water attachment and lawn mower throttle cable. Thanks for all of your input, Mike :)

[JohnsonM50]

I took the cone etc. off and the pump looks OK. Ill run it again when I get a chance to set up the custom-made [from junk] motor jockey with barrel-o-water attachment and lawn mower throttle cable. Thanks for all of your input, Mike :)
I just tried to run it again and still no water, next Ill have to take the lower unit out and see whats what. I made a copper tube [same size as stock], copied the end cut and length that goes from mid to foot and siliconed it into the foot adapter. Its the last thing I can think of. :confused:

[mercguy]

I just tried to run it again and still no water, next Ill have to take the lower unit out and see whats what. I made a copper tube [same size as stock], copied the end cut and length that goes from mid to foot and siliconed it into the foot adapter. Its the last thing I can think of. :confused:

I also drill and tap the sides of the foot adaptor to install a 1/4 hose fitting that taps into the hole in the foot adaptor for the water. Then, run another water inlet hose to the powerhead. The other side I just put in a 1/4 pipe plug. This also allows to make make a flush fitting that would thread into the tapped hole (that has the pipe plug), so that you could run your engine on the garden hose.

[JohnsonM50]

:cool: I like the idea of tapping into the sides of the adapter, got all weekend to think about it since Ill be away at a wedding. :eek:

[jeff55vDSH]

Just some food for thought.
I've worked on more than a couple OMC service motors that would not pump water. I looked and looked for a water pump problem. Came to find out the powerhead had a blown head gasket that was pressurizing the water jacket, making it impossible for the good water pump system to overcome. I replaced the head gasket and SHAZAM! pumped water again!

[JohnsonM50]

Just some food for thought.
I've worked on more than a couple OMC service motors that would not pump water. I looked and looked for a water pump problem. Came to find out the powerhead had a blown head gasket that was pressurizing the water jacket, making it impossible for the good water pump system to overcome. I replaced the head gasket and SHAZAM! pumped water again! Thanks Jeff, Ill check compression too. [Just replaced a worn tester]

[JohnsonM50]

Ive got one more question just in case.. Ive noticed that on my 1 to 1, older short skeg - multi inlet hole foot theres a bushing on the top mount surface where the cooling tube goes in about 1/8 to 1/4 and stops. On another 20H tower I have around the tube sticks out of the bottom about 2 in and has a slanted cut facing back towards the waterpump housing. Which of these types should be used for a long skeg single hole foot or are they interchangable? Thanks, Mike

[mercguy]

Ive got one more question just in case.. Ive noticed that on my 1 to 1, older short skeg - multi inlet hole foot theres a bushing on the top mount surface where the cooling tube goes in about 1/8 to 1/4 and stops. On another 20H tower I have around the tube sticks out of the bottom about 2 in and has a slanted cut facing back towards the waterpump housing. Which of these types should be used for a long skeg single hole foot or are they interchangable? Thanks, Mike


Mike, where the brass water tube enters the lower unit, there is a rubber grommet on top, then the bushing on the bottom. You can interchange lower units. The tube length varied over the years and the slant is not a factor, as the channel is much deeper than the tube depth. Hope this makes sense......

BTW, with the use of the tapped fittings on the adaptor plate, you will know exactly how much water is going to the powerhead by flow and visualization......

[JohnsonM50]

Mike, where the brass water tube enters the lower unit, there is a rubber grommet on top, then the bushing on the bottom. You can interchange lower units. The tube length varied over the years and the slant is not a factor, as the channel is much deeper than the tube depth. Hope this makes sense......

BTW, with the use of the tapped fittings on the adaptor plate, you will know exactly how much water is going to the powerhead by flow and visualization......
Thanks Daren