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.

[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.

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.

[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.

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.......

[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?