No cooling in reverse.

[Jayomc]

I'm at a complete loss at this point.

1989 28' harris flote bote with 3.0l merc and a OMC king cobra outdrive all seems stock.

Driving forward there usually is no issue but when put into reverse most of the time I have to watch the temp gauge to see if there's any water to cool the engine.

If it gets hot then I drive forward and get some water moving through the engine.

Water pump has been changed (twice) everything works when the muffs are on.

I don't know what to look at next.

 

[southkogs]

Re: No cooling in reverse.

Howdy Jay - welcome aboard.

How long you going in reverse, bro? I don't typically go into reverse long enough to matter - operating at 160? (normal for mine), even if I had to back outta' a small channel, I can't imagine climbing up to 200? too fast. Y'know?

I'm not 100% sure where your water pickup is on a Cobra, but I'm assuming their on the sides of the lower unit facing forward.

 

[Jayomc]

Re: No cooling in reverse.

Howdy Jay - welcome aboard.

How long you going in reverse, bro? I don't typically go into reverse long enough to matter - operating at 160? (normal for mine), even if I had to back outta' a small channel, I can't imagine climbing up to 200? too fast. Y'know?

I'm not 100% sure where your water pickup is on a Cobra, but I'm assuming their on the sides of the lower unit facing forward.

Santee Cooper fishing for cats, It is normal to reverse all day as slow as one can go, about .5 mph

Yes the pickups are on the sides of the lower unit.

 

[southkogs]

Re: No cooling in reverse.

Does it overheat at idle?

 

[Jayomc]

Re: No cooling in reverse.

Sometimes, it always works when going forwards and once its pumping it will at idle.

If i reverse and it stops pumping, just putting it in idle wont fix it. I have to move forward.

 

[jerryjerry05]

Re: No cooling in reverse.

Is the difuser ring still on the prop?
Pics of the prop and lower unit?

 

[Jayomc]

Re: No cooling in reverse.

I pulled the circulating pump out, looks fine.
At this point it does not want to pick any water up (its been sitting for 7 months)
I pulled the water pump off, its not burnt out, it looks just fine.
The whole thing works fine with garden hose water with muffs are put to the foot. (thermostat changed last year works)
By itself it just wants to over heat,

Next is to put the circulating pump back on, put the boat in the water, remove top water hose and see if the water makes it that far.
Any other things i can do or look at.

 

[Jayomc]

Re: No cooling in reverse.

I read this from another fourm "UN FRIGGIN BELIEVEABLE!!!!

So after sitting there in a state of flux since January, I decided to have another crack at finding the problem. I actually purchased another outdrive to swap and see if it was an internal issue or not. It turns out.. it was not in the drive. I disconnected every hose coming to and from the cooling system and backflushed the inlet once again. This time, i removed the two outer tranfer block and sealed the garden hose into the engine side of the inlet. After turning the water on,,it just trickled out the cavity's for 5 seconds or so..when all the sudden POP!!!
Water started pouring through unubstructed. I saw a wad of something come shooting out and found it...turns out there were some busy wasps that somehow made their way into the cooling system and made a nest in the inlet. I fugure it was loose in there and moved back a forward depending on RPM and pressure....
On the good side.. everything is working and i can get the outdrive off my boat blindfolded ni like 20 minutes ..
Happy boating peeps..and thanks for al the help!!!"

what does he mean by "two outer tranfer block"

 

[Lou C]

Re: No cooling in reverse.

the way to trouble shoot this is to put the boat in the water and put the drive down. Then remove the hose coming from the transom mount to the thermo housing. Hold the hose up and get someone to start the engine. If you do not get a 2"-4" head of water then you have a problem in the raw water supply system. Either the impeller is not pumping right, the wear plate is worn, there is a blockage in the line between the transom and the thermo housing, or the is a problem with the water tube or water tube grommets in the drive.
The Cobra lower unit is very similar to a Johnson or Evinrude lower unit. If the boat is stored in the water, marine growth can grow on the internal screen in the lower unit and in the water intake area inside the drive, eventually this can cause enough of a restriction to cause overheating. On mine I had a problem with barnacles growing on the inside of that screen, I wound up taking it out and painting the inside of the water intakes with anti fouling paint. This really helped my water flow issue.

It sounds like your raw water flow is marginal at idle and when you shift to reverse the turbulance coming off the prop is disrupting the flow of water to the intakes.

 

[Jayomc]

Re: No cooling in reverse.

@Lou C It was stored on a trailer, that second part sounds about right, but other then putting in a new impeller kit (again) i just dont know.

I could run from a cooler of water to the thermo housing intake with a small pump while I monkey with the water pump for some testing.

 

[HT32BSX115]

Re: No cooling in reverse.

I could run from a cooler of water to the thermo housing intake with a small pump while I monkey with the water pump for some testing.

That will not work. The pump MUST be submerged in water at the normal waterline or it will not prime.

You need to put the boat in the water and disconnect the raw water supply hose from the transom mount as Lou C suggests.

That's the only way you'll determine where to look for problems.


Regards,


Rick

 

[bruceb58]

Re: No cooling in reverse.

1989 28' harris flote bote with 3.0l merc and a OMC king cobra outdrive all seems stock.

This doesn't make sense at all. Have pictures?

 

[HT32BSX115]

Re: No cooling in reverse.

This doesn't make sense at all. Have pictures?

Yeah......everybody calls a Cobra a "King Kobra"......

 

[jerryjerry05]

Re: No cooling in reverse.

The floatboat is a project boat.
Built by the owner.
The KING COBRA is a sticker that's been put on a LOT of units.
It was used first on the Big Block Ford in 88.
Then they decided the 2.3 could be a King Cobra and 4.3 and anything where the sticker would fit.

 

[Howard Sterndrive]

Re: No cooling in reverse.

If i reverse and it stops pumping,

That sounds like an assumption that hasn't been verified by taking the hose off and measuring flow.
Need to do that.
It sounds like low rpm flow is just low. Could be poor sealing along the suction lines from the lower unit to the impeller housing.

but stuff like temp sender wire be rubbing on the shift linkage.... other electrical issues has to be eliminated.

I'd probably start with a compression test of the engine to ensure a head gasket issue isn't fighting with cooling water at low rpm.

 

[Jayomc]

Re: No cooling in reverse.

Sorry not king cobra, its a 2.5l gmc "merc" with a cobra 800

 

[Jayomc]

Re: No cooling in reverse.

Ill have some pics soon, When I had to get a new prop is when it was determined I had a cobra 800 foot.

 

[bruceb58]

Re: No cooling in reverse.

Ill have some pics soon, When I had to get a new prop is when it was determined I had a cobra 800 foot.

That will be good because there is no such thing as an 800 Cobra foot.

 

[Lou C]

Re: No cooling in reverse.

I'd like to see a pic of the transom when the boat is in the water. Is the top of the upper gear unit submerged? It should be for the impeller to prime. A few more tips:
Remove the plastic cover that covers the impeller the next time you test it on the water muffs. Look closely all around the housing, there should be no water seeping or squirting out. If so that rubber o ring gasket for the housing is not seated right. Also with the engine running pull off the little hose attached to the nipple on the impeller housing. Water should squirt out. If not that little passage is clogged. It has to be open to let the impeller prime (as the drive submerges, it lets air OUT so water can get IN).

Next if you take off the impeller housing again, try these 2 tests:

Get your water muffs put em on the lower unit and turn on the water. Hold the muffs tight to the lower and water should squirt out of one of the passages that is behind where the impeller fits. If not you have a problem withe the water tube grommets, water tube (rotted) or the intakes are clogged. Now take off the muffs. Remove the raw water intake hose at the Thermo housing. Stick you garden hose in the end of that hose. Have some one hold the garden hose in there and turn on the water and go look at the same water passages. Now water should squirt out of the other one. If not there is an obstruction th the hose, ps cooler or the transom to drive hose. Those are all the more common problem spots I know of....

 

[Jayomc]

Re: No cooling in reverse.

@ Lou C
- Yes top of the upper gear unit submerged
- on the muffs when running the nipple on the impeller housing does push water in a nice stream
- water does push up from the lower unit via muffs through the passages that is behind where the impeller fits
- water pushes back from the thermo housing raw water feed to the passages that is behind where the impeller fits and when the impeller is on to the foot intake

when the garden hose is put to it everything works, I will be testing volume of raw water going to the thermo housing once i get it back to togeather