5.0 GXI-N Cooling System

[JP_R]

I am doing a bunch of maintenance on a new boat that I just purchased and got the a point that I am a bit confused. Broker stated the boat needed new impellers and or new water pumps along with a few other items given the boat had been without use for a while.... I am doing all oils, impellers, plugs, gaskets, etc.....

Bought new impellers to start and to my surprise, current impellers look and feel perfect. Rubber is still in great shape and they look like they have not been used much since last replaced. Pump looks good too. Bearings spin fine and no strange grinding noises.

Engines run great when connected to flush fitting and they spill out lots of water. When connected to the muffs though, absolutely no water comes out via exhaust. I am new to Volvo engines so wondering what it could be?

I considered some kind of blockage on transom hose but the thing is that when the engines are off, lots of water comes out of the drive pickup.... that leads me to believe that if the water can flow down to the drive, then water should be able to flow up from drive to motor. Am I correct in thinking this?

 

[alldodge]

There is a flush fitting
Follow the fitting to see if there is a valve (manual or auto) which shuts off water going back to the drive.

If valve is open, then check the drive for a clog (maybe even things like mud dobbers)

 

[JP_R]

There is a flush fitting
Follow the fitting to see if there is a valve (manual or auto) which shuts off water going back to the drive.

If valve is open, then check the drive for a clog (maybe even things like mud dobbers)

thinking out loud here.... if when connected to the flush fitting (engines off) the water if flowing back and escaping via the drive pickups perfectly, wouldn't that rule out blockage?

 

[alldodge]

OK, you said water came out drive pickup, didn't catch the term

If the motors have been drained, did the motor run long enough to refill and let water exit?

 

[JP_R]

OK, you said water came out drive pickup, didn't catch the term

If the motors have been drained, did the motor run long enough to refill and let water exit?

yes, at this point I have ran the engines connected to the flush fitting a few times and even for 10-15 minutes at a time.

I just read another post where it states that if the muffs do not seal GREAT then they will not pressurize the system and impeller might now be able to pull the water.... I will also try with drive submerged on a tub.

I will retry holding the muffs as tight as possible and run the engine. My prior boat had a merc 5.0 MPI with an Alpha One so it was easy for the impeller to pull the water being on the drive.

 

[alldodge]

Don't do it with drive in a tub, this will burn up the impeller. The pump doesn't do much sucking, so it will not suck the water up. The muffs need to be tight.

Remove the inlet side of the hose going to the pump and with muffs connected see if water comes out (it should).

 

[Lou C]

Try the round Merc/Quicksilver muffs with the metal steel rod clamp these work better than the rectangular dual inlet ones.

 

[JP_R]

Try the round Merc/Quicksilver muffs with the metal steel rod clamp these work better than the rectangular dual inlet ones.

Thank you Lou. Will give them a shot if the current square ones don’t work.

Reality is that I just need to make sure that pump and impellers are working as they should. Moving forward I will always flush via the itting.

 

[bruceb58]

These are the best muffs. Put water on both sides

Moeller 380160 Moeller Marine Professional Dual Water Engine Flushers | Summit Racing

Free Shipping - Moeller Marine Professional Dual Water Engine Flushers with qualifying orders of $109. Shop Marine Engine Flushers at Summit Racing.

www.summitracing.com

 

[alldodge]

^^ the ones I use also

 

[Lou C]

The last ones of that style I bought (Tempo or Moeller square dual inlet muffs) the rubber was too stiff for them to conform to the lower unit contours and a lot of water was exited around the sides. The Merc/Quicksilver ones are much softer rubber and flex to the shape of the lower unit. That and the metal clamp makes them fit very tight and the impeller primes right away. There is also a round style made for V/P drives that might be worth trying if you have one.

 

[BRICH1260]

I`m confused. Have you tried the blue flush port on the starboard side of the engine, behind the fuel cell. That is what you should run your engines on. Are you doing that and not seeing the water exit?

 

[Lou C]

It sounds like he said it worked on the flush port but not with muffs.
Here's what I used.

 

[bruceb58]

The last ones of that style I bought (Tempo or Moeller square dual inlet muffs) the rubber was too stiff for them to conform to the lower unit contours and a lot of water was exited around the sides. The Merc/Quicksilver ones are much softer rubber and flex to the shape of the lower unit. That and the metal clamp makes them fit very tight and the impeller primes right away. There is also a round style made for V/P drives that might be worth trying if you have one.

You will always get water exiting from the sides. That is excess water that the engine can not accept. This is especially true before you start the engine. If the engine is not running, the water is not getting by the impeller.

BTW, at least on my Volvo drive, you can't use that Mercury type anyway. There is casting in the way that prevents you from putting anything all the way through. I have a Duo Prop drive. Maybe single prop drives are different.

 

[JP_R]

I`m confused. Have you tried the blue flush port on the starboard side of the engine, behind the fuel cell. That is what you should run your engines on. Are you doing that and not seeing the water exit?

I have! Via the flush port everything works perfectly. I wanted to try with the muffs to verify that pumps were working fine and pulling water in.

The boat has yet to go in the water as I am doing tons of service items. Next on the list is shifter cables, gimball bearings, and bellows

 

[Lou C]

I have! Via the flush port everything works perfectly. I wanted to try with the muffs to verify that pumps were working fine and pulling water in.

The boat has yet to go in the water as I am doing tons of service items. Next on the list is shifter cables, gimball bearings, and bellows

Well in either case if you use muffs or the flush port you have your water pressure helping the impeller move the water. The only true test is to put the boat in the water and test it under operating conditions. Normally, the raw water hose will be full of water due to the fact that its below the static water line of the boat. The things that can cause trouble in the water are a cracked water nipple in the pivot mount that can leak air in, when the boat's up on plane and similarly old, rotted or heat damaged water tube gaskets, or a rotted water tube which connects the lower and upper gear housings. These last 2 things can only be checked by splitting the lower and upper gear housings. So what you'll be looking for is does the impeller pump enough water to keep the engine and exhaust system cool at idle (engine approx 160*, exhaust may be between 90-115 degrees or so at idle, when getting up on plane the engine temp may drop slightly until you slow down and drop off plane, then it may temporarily rise to about 170-175, usually after idling a few minutes it will drop back to about 160, the exhaust may rise to approx 135 after coming off plane, but after idling a few minutes it will drop back to about 100 or so.
And keep in mind that the raw water pump is only half the cooling system so to speak, normal engine temps also depends on the exhaust being able to let warm to hot water exit fast enough to prevent heat build up. So the exhaust manifolds and elbows must not have clogged water passages so hot water from the engine can exit when the thermostat opens and lets hot water out of the engine via the exhaust. You can have a situation where the engine is not technically overheating but the exhaust system is, because it is partially clogged. This is why you should bring an IR Temp gun on your test runs to take readings of the engine (the intake manifold right under the thermostat will read about 10* lower than the dash gauge, it is about the closest to what the engine temp will read on the gauge) and the exhaust manifolds and elbows. You can then spot problems if anything is hotter than it should be.

 

[BRICH1260]

I bet you have a mud dobbers nest in the drive. Since the boat is new to you, I`d go ahead and pull the drives and use the time

 

[JP_R]

I bet you have a mud dobbers nest in the drive. Since the boat is new to you, I`d go ahead and pull the drives and use the time

We’ll the bellows will need replacing so I will be inspecting once we take the drives off.