Mariner MagnumII 150 / Mercury XR4 2.4L water intake/inlet - where is it?

I can't find my water intake (inlet)?

Here's a pic:


It's very different from every other XR4/Magnum II I can find on the internet which shows water muffs where I would normally expect the water inlets to be as shown in this photo I got from a YouTube video:



As you can see, I don't have water inlets where the muffs typically go. Are those slits at the front the water inlet? How would I fit muffs on those?

I put the lower unit into a water trough with water deep enough to cover those slits in front (that I think might be the water inlets) and idled the engine for maybe a minute or 2 but no water circulated (no water came out of the outlet tube) so either those slits aren't the water inlet or the pump isn't working, or maybe the thermostat is closed?

How long should I idle an engine waiting for the thermostats to open? I'm worried about overheating it. To test the water pump/impeller, could I temporarily remove the thermostats and idle the engine in water? Water should immediately circulate if the pump/impeller is working, right?

You have a "coned" unit and yes those holes are the inlet. You have to purchase a special set of muffs or use a trash can to operate out of water. The lower unit must be submerged above the cavation plate for it to operate. If its a 2.4L it will "pee" within a few seconds.. Is that a Stratos STV or Lazer its on??

Thanks for the reply fazbullet! The boat is a Shadow VT200. I was using a horse water trough so it isn't quite as deep as a trash can, I don't think I had the water above the cavitation plate so I'll get a trashcan or 55 gal barrel and try again.

Is that cavitation plate factory on that engine or an aftermarket item? And why would a 150HP engine have a coned lower unit? Aren't those typically used for high perf engines 200 HP and above?

For most folks the " pointy lower units , are obviously faster " by looking at them.----In fact they are not really beneficial untill you get to 60 MPH and above boat speeds I am told..

I took the housing off where I thought I'd find the thermostats and find no thermostats. And it doesn't look like it was intended to house a thermostat. Does my engine not have thermostats or are they elsewhere?

She still doesn't pee water so I guess the next step is to look at the impeller. Any other suggestions? Oh, the serial # appears to be 088347 if that helps? Does that mean 1988 model year?

Somebody has tried to Hi-Po the cooling system...The t-stats was removed and washers installing as restrictors, and the one in first pic is to big. Look and see if poppet valve has been dinked with..

Thanks for the info fazbullet - I'm looking into the poppet valve now looking at internet pics and YouTube videos. Is it located on the prop side between the 2 cyl banks down towards the prop? How would I know if it's been messed with? And what good does removing the thermostats do? Seems like it'll always run cold (too rich) until it warmed up?

What good does modifying the poppet valve do? I think I understand its function but can't imagine why anyone would modify it?

Post a pic of starboard side of block with poppet valve.....

So the poppet valve is on the starboard side? I'll take a picture tomorrow.

I took the lower unit off to look at the water pump/impeller - it needs replaced. But I had a question about my missing "engine rotation compensation fin". In a YouTube video for "Impeller Replacement - Mercury 150 Outboard Engine" he points out this fin that I don't have. Here's a screenshot:


Also, what's that hole I have the arrow pointing at? I don't think it's for exhaust.

I'm missing this fin:


Is this another intentionally removed thing by the PO? Why? The YouTube guy said it's to compensate for the engine rotation as it's not mounted exactly straight so isn't it necessary? Or does that cavitation plate make it not needed?

The square hole is for exhaust on cowling..the lower hole is for a mounting bolt. The "torque tab" was removed as yout prop(big ear chopper) would hit a standard tab.