Cooling & rotation help. Model number shows RH, but engine rotates LH

[FlyinRyan324]

I’m really stumped. I’ve spent hours searching google and forums and can’t figure out my issue. I had a mobile marine mechanic come out and change my oil, transmission oil, and impeller. I can do these things myself, but wanted to save time and test out this guy on a “simple” job.

My cooling was working perfectly fine (stayed at 160°) before he replaced my impeller. It appears he put the impeller housing on upside down when he put it back together ever though he said it’s “impossible” to screw this job up. Now, my boat overheated first ride out. Unfortunately for me, it took us 6 weeks to finally use the boat and question his job. He therefore believes I’m lying about it being my first ride out and won’t help.

When watching a ski dim video of impeller install on my same pump, it shows to keep that flathead screw on the outside if it’s a RH rotation motor. As per forums, people say the 2nd letter (a R or L) on your model number, will show you if you have a RH or LH rotation motor. He put it on with the screw pointing out (starboard side). I don’t blame him for this based on the model number. It’s confusing.

Looking back for pics, I found an old pic showing the impeller pump DIDN’T have the screw facing starboard. Then I did a slow motion video of the motor. Looking from the nose towards the rear of the motor, it’s spinning clockwise, so that means it’s counter clockwise (CCW / LH rotation) when looking from the rear. Also, it appears to me (correct me if I’m wrong) that the impeller was spinning the wrong way. See photos.

Now, the point I’m at is:
I’ve reversed the impeller housing to what I think is correct. The engine only cools when I have a hose blowing pressure in via the cooling hoses on the Nautique. I’ve verified this by watching water come out the exhaust and the impeller housing is cold. If I use the plunger (aka fake a lake), then it doesn’t seem to have enough suction to pull water through the cooling system.

Looking at my old impeller that he pulled out, and knowing my cooling system worked fine, this new impeller should still be “good enough” I would think. But just in case, I have 2 new ones on order.

What do you think is my cooling issue???!?!?! Could it really be just the impeller still? I checked for leaks between the intake grate and impeller housing, but only super small drips at the hose clamp areas could be found (only when blasting water through the lines). These leaks didn’t show up on the hose plunger.

Do you think I have a LH or RH rotating engine?

Do you agree I have a Ford 351 PCM motor? I just bought this 1990 Sport Nautique in April and put a good 10 hours on it before this maintenance point. I am coming from 10+ years of owning a ‘84 SN 2001, but I am no where’s near calling myself a mechanic. I hate wrenching, but will do it since ya know, it’s a boat.

Thanks in advance!
Ryan

[NautiqueJeff]

I would say your engine is a LH rotation engine.

Flip the water pump around (as you suspected), replace the impeller, and enjoy a nice cool engine. Make sure the impeller that was run dry did not disintegrate and send pieces into the cooling system.

Fire your mechanic.

[NautiqueJeff]

Here's some additional info on your engine.

[jpwhit]

I checked for leaks between the intake grate and impeller housing, but only super small drips at the hose clamp areas could be found (only when blasting water through the lines). These leaks didn’t show up on the hose plunger.

Your cooling issue doesn't sound like the impeller. It sounds like you have air leaking in on the suction side of the raw water pump. The hose between the intake grate and impeller is a suction hose. It's under negative pressure, water won't leak out of that part of the hosing, air will leak in. Even a very small air leak in that part of the plumbing can cause overheating. Since that part of the cooling system is under negative pressure, even a small amount of air leaking in expands to large bubble and displaces most of the cooling water. Especially at idle and lower engine speeds.

The reason you see the leak only on the water hose, is because the pressure from the hose does make that section positive pressure instead of the normal negative pressure when you're not forcing lots of high pressure water in with a garden hose.

[Jonny Quest]

Left v Right rotation. When looking from the rear of the engine (from the bell housing end) toward the front of the engine, a standard or L/H engine rotates COUNTER clockwise in the marine world. When looking from the front of the engine toward the rear, a standard or L/H rotates clockwise. This can be a bit confusing…

If the PCM engine ID tag has “PLD” as the first 3 letters, you have a standard rotation with a 1.23:1 transmission. This assumes the engine hasn’t been secretly changed out for a reverse-rotation “righty”.

JQ

[fly135]

I diagnosed my pump being upside down by taking off the output hose and pouring water in when running. If it sucks up the water, it's backwards.