Offshoreonly.com - Transom water pickup vs through hull

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One riser being slightly warmer than the other is 100% normal. Both my 502mpi's do it as well.

Quote:

Originally Posted by SabrToothSqrl (Post 4788461)

I had a bad gasket/leak between combustion chamber and cooling system. I would compression test it, but it may not show at low RPM either. I think a few drops of water under the oil cap when cold is normal. Engines run hot enough to evaporate it then.
My one engine (ironically the running one) oil came out like a milkshake 2 years ago. I have a video of doing a cooling system test as well, where you can see air going into the cooling system at idle, indicating the leak between the combustion chamber and cooling system... it's a trick I was taught on another forum to trace cooling issues, by replacing sections of the OEM hose with clear hose. You can see the water from the raw water impeller has zero air in it. Then water leaving the block has air in it. Not ideal ;)

I replaced both of my engines 2 winters ago. Gained exactly 0 mph over the engines that both failed compression on multiple cylinders. and one was an intermittent no start for 2 years, the other was milkshaked.

SabrToothSqrl
On your comments about no speed loss with low compression. I recently had one motor with 2 cyl low on compression. Stock comp was 165. I only lost 1/2 to 1 mph when the compression was 75psi on one cyl and 90 psi on the other. Goes to show you that you can run a while on a motor with compression that's a little low. Won't even know the difference. I think Mercury says 100psi minimum. I agree, I would run it above that. If you've been a boater for awhile with BBC, you know it's just a matter of time, before you have to take it apart anyway for some other reason. Hopefully a few years though. Seen motors last thousands of hours, but in most cases, something else gets them besides normal wear. Good luck.

Quote:

Originally Posted by SabrToothSqrl (Post 4786377)

...why? MerCruisers number in the millions and all work fine...

I can only assume the boat worked fine new, and works now?
Do you have an issue you're trying to correct?
If not - leave it alone... go for a run and enjoy it...

For closed-cooled systems Mercruiser requires additional water pickups either through transom or hull. I'm about to install one and have the same dilemma where and how to put additional water pickup. Any hints would be appreciated.

Quote:

Originally Posted by Paraplan (Post 4907230)

for what drive application?

I run Bravos with closed cooling on 800HP motors and my temp never moves off 150 - EVER!!

The Bravo pump moves a LOT of water…..

Quote:

Originally Posted by seafordguy (Post 4907272)

for what drive application?

I run Bravos with closed cooling on 800HP motors and my temp never moves off 150 - EVER!!

The Bravo pump moves a LOT of water…..

Per 8M0085598 Closed Cooling Kit Instruction manual:

Notice
IMPORTANT: Bravo models with closed cooling require a through‑the‑hull or through‑the‑transom pickup in addition to the sterndrive water inlets to meet the minimum flow specifications.

Interesting.... my 525s set at 150 all the time and get water only thru the Bravo drives....

Quote:

Originally Posted by im MartinB (Post 4907278)

Interesting.... my 525s set at 150 all the time and get water only thru the Bravo drives....

My HP500EFI's with only a bravo LWP do the same thing, I have changed the thermostat once in 24 years and ran salt water the last 12. Granted open cooling but still, 790Hours.

I run a 800hp whipple supercharged 496 and with a 5" dia heat exchanger, it never gets above 150 degrees at 9lbs of boost. That's also running a 13 plate box oil cooler. All that is cooled via a low water pickup XR drive.

Quote:

Originally Posted by Paraplan (Post 4907277)

I’d try it using the standard Bravo pickup before you turn it into a goat screw.

https://cimg1.ibsrv.net/gimg/www.off...0653de6c6.jpeg

Quote:

Originally Posted by Paraplan (Post 4907230)

since when? Every mercruiser sterndrive I have ever worked, that was close cooled, got its water thru the drive