Is this normal water flow? Bravo 2 outdrive

[dwolsk2]

Hello

I was wondering if anyone can verify if the water flow i have coming from the transom to my raw water pump is sufficient?
1998 Maxum 2700 SCR
5.7 Mercruiser 2-barrel
Bravo outdrive.

I started a thread earlier on air in the cooling system. If anyone else has any ideas or tests I'm happy to try them.


Thanks in advance

-Dan

 

[dwolsk2]

Here's one of the videos with air in the cooling system.

 

[alldodge]

If your first video is with the engine off (I think it is) then the flow is equal to the hose being barely below the water level of the boat. Now if the exit hose is below the water level of the boat then you have a restriction.

The second video leans me to where you may have an air leak in the intake hose/line/fitting

 

[Fun Times]

The water flow in the first video!! Is that the hose from the transom assembly disconnected from the sea water pump? (< Pump intake side).

Are you using a garden hose or is the boat sitting in a body of water?

The info below is from Page 6A-5 + in the following link,
COOLING SYSTEMS - Boat Parts, Marine Engine Parts, Boat ...
Seawater Pickup Pump Output Test If an overheating problem exists, use this test to determine if a sufficient amount of water is being supplied to cool engine.
IMPORTANT: The following information should be observed before proceeding with test:
&#149; BOAT MUST BE IN THE WATER FOR THIS TEST. This test CANNOT BE performed with a flush-test device and water hose.
&#149; The ability of this test to detect a problem is greatly dependent upon the accuracy in which it is performed. An error in setting the engine RPM, timing the test or measuring the water output will affect the overall accuracy of the test and may produce misleading results. To help ensure accurate results, a shop tachometer with an error of less than 5% should be used. The boat tachometer definitely should not be used as its accuracy is questionable. A stop watch should be used to time the duration of the test to help ensure that the accuracy is maintained within one second. An 8 qt. (7.6 L) or larger capacity container calibrated in 1/4 qt. (250 cu. cm.) increments should be used to measure water output.
&#149; Due to the manner in which this test is performed, it may not be possible to detect a marginal condition or a high-speed water pump output problem.

b. Belt Driven Seawater Pickup Pumps: (Bravo) Remove water hose, which runs between pump outlet and engine, and replace with another hose of same diameter, but approximately 3 ft. (1 m) longer. Hose should be wire reinforced or of adequate wall thickness to prevent it from kinking when performing test. Clamp hose at pump outlet only. Do not clamp hose at engine end.

2. Repeat test four times to check repeatability of results.
Alpha

Belt Driven Pump Output for 15 Second Period
7.5 U.S. Qt. (7.1 L) Minimum

 

[muc]

The end of the second video showing air in the intake hose of the sea water pump. If this was taken with the boat in the water, tells you that there is a suction leak somewhere between the pump and the water pickup that you must find.

 

[dwolsk2]

Thanks for the quick responses. I forgot to clarify that YES the boat is in the water, not on muffs. The hose shown is the inlet hose from the transom.

-Mr AllDodge if the boat is in the water, is it possible for the pickup hose to be in a position just barely below the water line? I was trying to confirm that myself. The outdrive is completely submerged but if i remember the routing of the water pickup hose it was almost near the top of the outdrive housing. My initial assumption was that when i remove the inlet hose ( which is the hose that goes to the inlet side of the sea water pump... i just had a section of clear tubing when i tested for bubbles on the inlet side) i would've been bum-rushed with water..... that obviously didn't happen. The water pickup hose is new. I did a complete bellows service last year. Is it possible the hose is collapsing?

-Mr Fun Times yes that hose is the intake side of the raw water pump. Before i had installed these clear tube sections I had completed that specific flow test you had listed in your response, and each time i had passed. The water flow on the outlet side was filling half of a 5 gallon bucket in the time frame required (15 seconds).
I apologize but i should've started my post with my original problem that i am chasing. I have an overheat issue (slow temperature climb, idle to low rpms are fine) above 3000 rpms. Manifolds, risers, elbows are all new. Pump is new, and i backflushed the cooling system. That is why i'm trying to rule out cooling before i jump on the head gasket.

-Mr Muc do you have any suggestions on how to find a suction leak in that area? It's basically the 1 1/4" steel reinforced hose, coupled to the inside transom fitting, then the water pickup hose which is eventually submerged. This is what i'm struggling with.... where else can a leak form in this section water routing? I completely agree with you, it's like trying to suck through a straw that has a hole in it. Is there some component I'm missing.

So far thanks again guys for the responses. Now i know for certain no air should be coming in through the inlet.
I guess i'll have to pull her out of the water and take the leg off.

-Dan

 

[Fun Times]

The water flow from the intake hose does seem just a little on the slower side knowing the boats in the water so you may want to check for the type of damage at the intake water fitting like seen in the following link, http://www.amarket.com/BRAVOblock.htm

If the area behind the fitting seems okay, then you'll want to check the bell housing to transom intake water hose, then remove the drive and inspect the water passage area and O-Ring at bell housing.....If okay then there's also an O-Ring between the upper and lower stern drive unit that could be compromised.

Hope for the best, good luck.

 

[muc]

I would also check the water hose where it goes thru the gimbal housing. MerCruiser has had some problems with corrosion that causes reduced flow or suction leaks.

To test for leaks, pull the drive, cap one end and apply pressure to the other end.