No cooling in reverse.

Lou C

Lou C

Supreme Mariner
Joined
Nov 10, 2002
Messages
13,065
Re: No cooling in reverse.

Well then take it off, and make sure the gasket is seated properly because they can get out of place when you are putting it on. There should be no drips etc when you run it on the hose.
 
bruceb58

bruceb58

Supreme Mariner
Joined
Mar 5, 2006
Messages
30,589
Re: No cooling in reverse.

Another few things to try requires the boat to be in the water.

1) Remove the hose where it goes to the thermostat housing and see what your flow is like there.
2) Put a short piece of clear hose between that hose and the thermostat housing to see if there are any air bubbles in there indicating an air leak at either the raw water pump itself or between it and the water pickup at the drive.

Have you removed the thermostat housing to make sure it is completely clear of any rust, debris or old impeller blades?
 
J

Jayomc

Cadet
Joined
Nov 22, 2013
Messages
23
Re: No cooling in reverse.

bruceb58 said:
Another few things to try requires the boat to be in the water.

1) Remove the hose where it goes to the thermostat housing and see what your flow is like there.
2) Put a short piece of clear hose between that hose and the thermostat housing to see if there are any air bubbles in there indicating an air leak at either the raw water pump itself or between it and the water pickup at the drive.

Have you removed the thermostat housing to make sure it is completely clear of any rust, debris or old impeller blades?
Click to expand...

Thermostat works fine with garden hose pressure,
Pushed water from foot to the hose disconnected from thermo housing, lots and lots of water
Good idea on the clear hose for bubbles, it should be 1" id hose?
 
bruceb58

bruceb58

Supreme Mariner
Joined
Mar 5, 2006
Messages
30,589
Re: No cooling in reverse.

Jayomc said:
Thermostat works fine with garden hose pressure,
Click to expand...
I would still look. Its just that its on the marginal side right now and using the garden hose may mask if its a marginal flow caused by it. The only cost will be a new gasket.

Leave no stone unturned!
 
Last edited:
H

HT32BSX115

Supreme Mariner
Joined
Dec 8, 2005
Messages
10,083
Re: No cooling in reverse.

bruceb58 said:
Another thing that is unusual with this setup is how high the drive sits in the water. Typically at idle, the water line would be at least at the level of the impeller. Seems like this is setup, the impeller is sitting above the water. This makes it way harder for a raw water pump to keep its prime. Any air leaks at all are going to affect it greatly.
Click to expand...

This is fairly important! Most ALL stern drives are designed to sit in the water with a resting water line far HIGHER (ON THE DRIVE)! It's not as much a problem with a Mercruiser Alpha, (and probably most outboards) because the raw water pump is located physically LOWER in the in lower unit. This puts them in the water so there's water in them when you start the engine.

If you locate the pump higher, like in your case (or with a Bravo, or Volvo) , That makes it MUCH MORE important to ensure that there is NO leaks in the raw water line between the pump and the water line. If there are leaks, then you suck air when you start the engine.............. if it's enough air, THE PUMP DOESN'T prime immediately (or at all) ........if it's just a little air, the pump "runs dry" briefly while water is making it to the pump. This can wear the pump out quickly if it takes too long.

In any case, you can check by replacing the transom raw water supply hose with a clear vinyl hose. Then start the engine and observe looking for bubbles.

If there's no bubbles, then you can disconnect from the t-stat housing and observe flow rate at idle, fast idle etc.....
 
Last edited:
J

Jayomc

Cadet
Joined
Nov 22, 2013
Messages
23
Re: No cooling in reverse.

From the impeller to the foot are channels for the water to run in, (correct ?)
Where else might I get air in the system besides those to places?
I looked at the screen foot intake holes tonight and they are clean
Ill get the impeller 100% tomorrow.

And thanks for all the help so far!!!
 
bruceb58

bruceb58

Supreme Mariner
Joined
Mar 5, 2006
Messages
30,589
Re: No cooling in reverse.

There is a water passage the connects the lower to the upper gear cases. Check out the parts in the upper left of the diagram.
OMC Stern Drive Lower Gearcase Parts for 1989 3.0 L 302AMRMED Stern Drive

Normally, even if these leaked, you wouldn't have an issue but since your drive sits so far out of the water, these parts may actually may not be submerges in water. It may be an issue in your case.

If the drive was ever taken apart and these weren't put together correctly, it could possibly be your problem.
 
Last edited:
Lou C

Lou C

Supreme Mariner
Joined
Nov 10, 2002
Messages
13,065
Re: No cooling in reverse.

Well when you look at the impeller mount area, the flat surface that is horizontal underneath the impeller housing is right above the upper grommet for the water tube. If this is above the water line, and that grommet was worn or leaked that could be part of your problem. I've had the upper and lower apart 2x to clean barnacles out of the water intake area. The upper grommet and tube get put in the upper gear housing right under the impeller. A plastic guide fits into the lower grommet in the lower gear housing, the guide actually guides the brass water tube into the grommet. It's not hard to do it right but you never know.
 
Last edited:
J

Jayomc

Cadet
Joined
Nov 22, 2013
Messages
23
Re: No cooling in reverse.

Circulation pump is in, silicone all around the impeller, raw water intake hose has a chunk of clear tub and a rad flush part.
Put it in the water and the first 3 starts I have raw water. :)

It has not run long enough to heat up and do more test, tomorrow will be the the day.
 
bruceb58

bruceb58

Supreme Mariner
Joined
Mar 5, 2006
Messages
30,589
Re: No cooling in reverse.

Not sure if silicone is the best thing to use or not for down the road. Gasket sealer on the impeller housing and the plate that it mounts to would probably be best. Its good if this solved the issue as now you know what was causing it.
 
Lou C

Lou C

Supreme Mariner
Joined
Nov 10, 2002
Messages
13,065
Re: No cooling in reverse.

Good that you're using the clear hose test, because at least then you can see for yourself what's happening. If the gasket seals around the impeller housing and the water tubes in the drive are sealing well, then it should prime. I would use OMC gasket sealer or similar (Permatex aviation sealer) on the gasket and wear plate gasket for the impeller. If the motor has ever had a bad overheat, you can have burned and slightly melted water tube grommets because the exhaust water all goes through that area. If you lose the flow of cooling water the hot exhaust can melt them and can melt that plastic guide that fits into the lower one. When you are backing up is the drive all the way down? If you are tilted up, because your drive is a good 2" higher than the optimal height that could be adding to your problem. If the water is deep enough try keeping it all the way down.
The height of the drive and reverse thrust of the water when in reverse are factors that are making it harder to prime. With the prop turing in reverse, it is forcing water past the water intakes and there is no natural forward motion to force water in the intakes. So your raw water system has to be perfect to get it to prime.
 
Last edited:
J

Jayomc

Cadet
Joined
Nov 22, 2013
Messages
23
Re: No cooling in reverse.

So, today after i got my circulator to not leak, I noticed when I first start the engine there was no water, i give it a shot of high throttle and the water pumps.

While the water is pumping i removed the rad flush cap and have a jet of water a little over a foot long.

I ran it through its paces forwards and backwards fast and slow and as long as I can see the clear tube the $#%%er is working.
No air just lots of water.
 
Last edited:
You must log in or register to reply here.
Top