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One riser being slightly warmer than the other is 100% normal. Both my 502mpi's do it as well.
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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. 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. |
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... |
Originally Posted by Paraplan
(Post 4907230)
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.
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….. |
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….. 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....
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Originally Posted by im MartinB
(Post 4907278)
Interesting.... my 525s set at 150 all the time and get water only thru the Bravo drives....
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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.
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Originally Posted by Paraplan
(Post 4907277)
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. https://cimg1.ibsrv.net/gimg/www.off...0653de6c6.jpeg |
Originally Posted by Paraplan
(Post 4907230)
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.
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Originally Posted by obrien
(Post 4907424)
since when? Every mercruiser sterndrive I have ever worked, that was close cooled, got its water thru the drive
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Originally Posted by Paraplan
(Post 4907426)
The official Mercruiser closed cooling kit requires it. It is in the manual.You probably have an aftermarket kit.Of course, there is nothing that can stop you not to install additional pickup.
Edit: I just cruised through Mercurys parts catalog and can not find that part number, care to share a link to this information? |
Originally Posted by Wildman_grafix
(Post 4907448)
I do not get that, I have friends with both factory Merc closed cooled 525's, 600SCI and they all used the factory water pickup through the drive. Pretty sure the 39 Velocity with 565's also did.
Edit: I just cruised through Mercurys parts catalog and can not find that part number, care to share a link to this information? |
If you go through this catalog, it is Y-shaped fitting, part #2, that connects to alternative transom/hull water pickup.
http://www.boats.net/catalog/mercrui...g-system-bravo |
and moreover, Mercrusier's official closed-cooling kit (part 864920A02) requires an ECM change. Fortunately this one is a free swap, you buy a new one (part 866125T06) and return your original one for refund.
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Originally Posted by boater24178
(Post 4788474)
I already did all that stuff and also put on a drive shower. The Bravo 3 drive is working fine.
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Interesting.
maybe because it’s a full system and they feel they need more flow to cool exhaust? I stand by my comment - I’d install without initially and monitor your temps. They move a LOT of water and I’ll bet you won’t have any issues. |
Thank you for the link.
Like seaford said that is a full system including the exhaust (nice) when most performance installs do not cool the headers with the closed cooling. I would try it without if you are using it on something like a 300hp 5.7 and monitor. Unless the motor is out already. |
Running a full system off the Bravo raw water feed depends on a few factors. Boating location and expected raw water temps. Exh manifold size and style. Fresh water circulation flow through the heat exchanger.
Generally, fresh water heat exchanged engines run a bit warmer at a 160°F thermostat, where the temp differential in the heat exchanger is greater. Also having a consistent block coolant pressure etc. Often the full systems have the thermostat in the heat exchanger, to enable coolant flow through the exh manifolds before thermostat opening. Will also warm up the engine faster. One of the potential coolant flow bottlenecks is the exh manifolds. |
Originally Posted by JaayTeee
(Post 4907499)
What are you doing with the water that use to come thru the drive?
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Originally Posted by CheckmateScarab
(Post 4907554)
You can use it for the drive shower if you wish. I cut my tube from the upper to the helmet and just let the water dump
It’s worth it |
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