Bravo 1 low water pressure

[skyman2112]

Hi group, still having the same problem here. When engine is warm and thermostat is open, i dont have enough back pressure to build up enough water pressure fast enough to keep the alarm from going off. When the engine is cold it immediately jumps to 2.5 psi and doesnt have any problems. This rules out any intake restrictions, sensor errors, or pump issues. When the engine is warmed up, it takes about 25 seconds to get above 1psi.
This was the first year of the Catalyst motors, so i suspect there is too much water being sent to the exhaust and cats. I checked the poppet valve and the elbow used to send water to the cats and they seem to be fine, and correct (green) fitting. Is there some kind of mod i can do to increase back pressure so i dont get the alarm when starting the engine warm? Its never ran hot and the alarm always clears itself, its just annoying. Thanks in advance

 

[alldodge]

Serial number?

Is the impeller new?

 

[QBhoy]

Hi
Can I ask where you are reading the pressure from (is it an analog gauge or from the smartcraft) ?
And also if the boat is on a trailer or out the water when you find this ? I know that you’ll get next to nothing reading on the smart craft when you’re out the water and no back pressure. But don’t ever remember an alarm. You certain the alarm is for water pressure?

 

[tpenfield]

The OP mentioned that this is the first year of the CAT engines, so guessing around 2012-23 . Bravo 1 does not have much to do with it, unless it is Bravoitis.

Yes . . . engine & serial number would be good.

BTW - I'm fighting with the port engine . . . similar thing . . . low water pressure.

 

[tpenfield]

Just found the OP's boat/engine on a prior thread . . .

2011 Crownline 21SS with a 6.2L 377 MAG w/cats, Bravo 1,

S/N is 1A645849

Also do you have closed cooling or 'standard' cooling? I'm guessing closed cooling based on the Popeye valve

 

[alldodge]

Might be the check balls on the exhaust

Assuming it's open cooled

 

[skyman2112]

Just found the OP's boat/engine on a prior thread . . .

2011 Crownline 21SS with a 6.2L 377 MAG w/cats, Bravo 1,

S/N is 1A645849

Also do you have closed cooling or 'standard' cooling? I'm guessing closed cooling based on the Popeye valve

 

[skyman2112]

Might be the check balls on the exhaust

Assuming it's open cooled

Impeller is new and so is pump. Check balls would definitely keep me from having enough back pressure. How do you check those?

 

[skyman2112]

Just found the OP's boat/engine on a prior thread . . .

2011 Crownline 21SS with a 6.2L 377 MAG w/cats, Bravo 1,

S/N is 1A645849

Also do you have closed cooling or 'standard' cooling? I'm guessing closed cooling based on the Popeye valve

Haha yes thanks for finding my old post, Its standard cooling, the poppet valve is in the thermostat housing

 

[skyman2112]

Hi
Can I ask where you are reading the pressure from (is it an analog gauge or from the smartcraft) ?
And also if the boat is on a trailer or out the water when you find this ? I know that you’ll get next to nothing reading on the smart craft when you’re out the water and no back pressure. But don’t ever remember an alarm. You certain the alarm is for water pressure?

Yes im sure its for water pressure, all testing is done with the techmate pro scan tool and the boat in a fresh water lake with open cooling. Impeller and pump housing are new with great pressure on cold starts, just slow to build pressure when warmed up. Pressure is fine in cruise always.

 

[Scott Danforth]

use a mechanical gauge, not the failure prone mercruiser sensor to validate water pressure.

check for bravoitis.

 

[QBhoy]

Yes im sure its for water pressure, all testing is done with the techmate pro scan tool and the boat in a fresh water lake with open cooling. Impeller and pump housing are new with great pressure on cold starts, just slow to build pressure when warmed up. Pressure is fine in cruise always.

Ok. The sea water pressure sensors are quite often known to fail on these particular engines. But i guess that would show nothing at all or irrational readings perhaps.

 

[tpenfield]

. . . . boat in a fresh water lake with open cooling. . . great pressure on cold starts, just slow to build pressure when warmed up . . .

OK . . . the additional detail is helpful.

First thing is . . . I don't think there is a problem as long as you are getting some pressure and not running hot at any range of speed.

Keep in mind that when the engine is cold, and the thermostat is closed, essentially the 'volume' of water flowing through the cooling system is less, since the water in the engine block is recirculating (so it warms up) for the most part. The sea water pump has an easier go of it and the pressure probably reads accordingly. As the engine warms up, the entire volume of the 'active' cooling system is larger and flowing both to the engine block and the exhaust . . . more places for the water to go . . . probably a lower pressure reading at idle speeds.

IIRC . . . the cooling water pressure on my engines is around 2 psi at idle speeds and around 20 psi at cruising speeds. The only cause for concern would be a dramatic deviation from the norm.

 

[04fxdwgi25]

If there is a possibility is is a questionable sender giving a false reading, the water pressure senders do go bad quite often. There is a quick fix in this video to see if it is the problem.

 

[alldodge]

Impeller is new and so is pump. Check balls would definitely keep me from having enough back pressure. How do you check those?

Don't know for sure but I would Connect a garden hose to lower side. Turn water ON but at low flow. The check balls should restrict the flow a good amount

 

[skyman2112]

If there is a possibility is is a questionable sender giving a false reading, the water pressure senders do go bad quite often. There is a quick fix in this video to see if it is the problem.

no possiblilty at all i replaced it many times same result. If it was faulty it would do it wether the engine is hot or cold. Thanks again

 

[skyman2112]

Don't know for sure but I would Connect a garden hose to lower side. Turn water ON but at low flow. The check balls should restrict the flow a good amount

So use the muffs and see how much water comes out the bypass ports on the sides or the exhaust through the prop? Engine off?

 

[skyman2112]

OK . . . the additional detail is helpful.

First thing is . . . I don't think there is a problem as long as you are getting some pressure and not running hot at any range of speed.

Keep in mind that when the engine is cold, and the thermostat is closed, essentially the 'volume' of water flowing through the cooling system is less, since the water in the engine block is recirculating (so it warms up) for the most part. The sea water pump has an easier go of it and the pressure probably reads accordingly. As the engine warms up, the entire volume of the 'active' cooling system is larger and flowing both to the engine block and the exhaust . . . more places for the water to go . . . probably a lower pressure reading at idle speeds.

IIRC . . . the cooling water pressure on my engines is around 2 psi at idle speeds and around 20 psi at cruising speeds. The only cause for concern would be a dramatic deviation from the norm.

I agree, theres less backpressure when the thermostat opens, so less pressure at startup when its warm. Always runs fine, just trips the alarm when starting it after warmed up. Just an annoyance!!

 

[alldodge]

No
The valves are below the exhaust Mans, and any place where there is a self drain check valve

(Did I mention I hate self drain systems)

 

[skyman2112]

use a mechanical gauge, not the failure prone mercruiser sensor to validate water pressure.

check for bravoitis

only does it when warmed up, builds pressure right away when its cold and thermostat is closed. Maybe it needs more flow and cant get it when the thermostat is open. But it never runs hot. i did run a cam up through the transom just saw some surface corrosion nothing major