112 spl overheating

[Steve Wheeldon]

I have a 112 spl runs great 120 psi on all cylinders I just replaced thermostats and water impeller low idol it's fine seconds into plane alarm goes off says I'm overheating and the motor stalls dont know if that's normal or not just getting really frustrated

 

[interalian]

Crossflow assumed, sounds like the water deflectors have dislodged and are blocking flow. Have to take the heads off to look/replace. But if you just replaced the water pump impeller, you might want to go back and check your work.

If the motor stalls at speed when the hot alarm is on, you may be 'hot seizing' the pistons. Not good.

 

[racerone]

The 112 HP model was only marketed as a crossflow design.------Was the 120 PSI before repeated stalls with horn coming on ?----Time for a repeat on the compression test I would say.

 

[Steve Wheeldon]

Still had good compression on all I removed the heads pistons and cylinders look great deflectors look ok I think I'm starting from scratch and redoing pump I did notice water shooting steady stream out of back of lower unit on hose going to start there

 

[rothfm]

The stats are located "last" in the water flow...Its easy to pop the hoses off, and notice the water flow. With hoses water should be strong and steady. If not, you either are not "introducing" water from the impeller, or you have a block restriction.

 

[rothfm]

Measure head temps with a thermal IR type gun as well.

 

[James R]

Sounds like you failed to install the impeller correctly. Did you rotate the driveshaft clockwise as you pressed the pump housing down over the impeller to correctly orientate the fins. Running on a hose does not tell you that the pump is working. It tells you that the faucet pressure is good. He told me that he tested the cooling with the hose and it was good. He put it in the lake and then called me to rebuild it. No kidding.
Hope we can help you.

 

[interalian]

Sounds like you failed to install the impeller correctly. Did you rotate the driveshaft clockwise as you pressed the pump housing down over the impeller to correctly orientate the fins. Running on a hose does not tell you that the pump is working. It tells you that the faucet pressure is good. He told me that he tested the cooling with the hose and it was good. He put it in the lake and then called me to rebuild it. No kidding.
Hope we can help you.

If you install the impeller backward, the vanes will flip once the engine is running. Water pressure is amazing.

 

[oldboat1]

I would do a couple of simple tests with the motor not running. Drop the l.u., and rig a connection from the hose to the water tube. Run the water at about half pressure, and see if the water circulates through the cooling passages and exits out the leg. You are looking for an obstruction — can help to have an IR gun to check temps. In this case, look for temps of about 40F throughout (approximate temp of incoming hose water).

The second step is to check the operation of the impeller. First spin the driveshaft clockwise by hand — should feel and hear the impeller if it it turning properly. Next, you can spin the shaft with the l.u. immersed in a tub of water. Spinning the shaft with a hand drill, water should bubble up from the water tube grommet in the pump housing.

 

[James R]

Interalian I must disagree. I have had more than one motor in here with some of the fins in the wrong direction and poor water flow as a result.

 

[oldboat1]

Think interalian has it right:

The impeller cup is slightly elliptical rather than round (shaft offset, I believe), so there is a point in the impeller’s rotation where the fins straighten out, then would self correct if they were installed backwards. Additionally, the fins flatten against the hub when the motor is revved, then contact the cup again when speed slows (direction again self-correcting).

I guess if you drop the l.u. and rotate the shaft counterclockwise by hand, it’s possible one or two of the fins would be reversed — maybe all of them with continued c.clockwise rotation.

 

[interalian]

Rubber water pumps operate as positive displacement (sealed to the housing) at low speed, then gradually become centrifufal as speed rises and the fans bend against the resistance of water and float away from the surface of the cup.