No cooling in reverse.

[Jayomc]

Re: No cooling in reverse.

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

Foot might be wrong but as the only difference from the cobra 400 and 800 sterndrive is the foot, its how I wrote it.

GLM Products Inc - 30 Years of the OMC Sterndrive
OMC 800 Water Pump Questions & Answers
OMC Cobra Sterndrive Tech Info

 

[bruceb58]

Re: No cooling in reverse.

OK...typically, Cobras aren't described that way. Only stringers typically use the 400/800 designation.

 

[bruceb58]

Re: No cooling in reverse.

Look at the hose that goes form the pivot housing up to the transom housing and make sure its not kinked.
#37 in the following picture.
OMC Stern Drive Transom Mount Parts for 1989 3.0 L 302AMRMED Stern Drive

On the inside of the boat, also make sure the hoses that go to the power steering cooler(if you have power steering) are also not kinked.

So, this engine that you have was originally used with a Mercruiser and put into this boat? Have you verified that the hoses were hooked up properly? Not sure if Mercruiser does anything differently than OMC on their 3.0L engine hook ups

 

[Jayomc]

Re: No cooling in reverse.

 

[Jayomc]

Re: No cooling in reverse.

 

[Jayomc]

Re: No cooling in reverse.

 

[bruceb58]

Re: No cooling in reverse.

Looks like you have a Mercruiser spark arrestor on the original OMC engine.

 

[Scott Danforth]

Re: No cooling in reverse.

why did you pull the circulating pump?

 

[Jayomc]

Re: No cooling in reverse.

I was at a loss what else could be the problem and pulled the circulating pump, in hindsight i didn't need to, now I'm waiting on a gasket.

 

[QC]

Re: No cooling in reverse.

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.

And I suspect the exhaust as well Does anybody know anyone that operates a boat like this? I am not saying that it is wrong or bad, but I suspect any thru prop exhaust system could be hampered by extended operation in reverse. Never thought about it before.

 

[Howard Sterndrive]

Re: No cooling in reverse.

the only thing Mercruiser is the flame arrester someone took off a Mercruiser engine and stuck on yours

 

[Jayomc]

Re: No cooling in reverse.

And I suspect the exhaust as well Does anybody know anyone that operates a boat like this? I am not saying that it is wrong or bad, but I suspect any thru prop exhaust system could be hampered by extended operation in reverse. Never thought about it before.

The exhaust from the bellows is not touching the water, to eliminate this, the bellow was removed and tested, the exhaust is not a factor at this time. (but noisy as 10 Harley's)

there was a new bellow put on last year with the back pressure holes built-in still noisy but not likely a factor.

The marginal raw water flow i think is the problem. i hope to have it tested today.

 

[QC]

Re: No cooling in reverse.

I had a 3.0 Stringer, so I know that sound. LOL

 

[bruceb58]

Re: No cooling in reverse.

I doubt much exhaust will be coming out of the prop at idles speeds, especially in reverse. Probably most of it will be coming out the relief ports.

Also, OP says that just putting it in neutral at idle doesn't fix the problem. Has to be an obstruction somewhere(old impeller blades, kinked hoses, thermostat not opening all the way, clogged exhaust manifold) or a bad raw water pump housing.

What is the general condition of the raw water pump housing and plate? Have you replaced the o-ring and used gasket sealant when reinstalling?

 

[bruceb58]

Re: No cooling in reverse.

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.

 

[Lou C]

Re: No cooling in reverse.

That's why I asked the question a few posts back. Also if you look closely at the pic of the water intakes, there is something in there, can't tell for sure what. I'd want to clean that out first and replace the water tube grommets

 

[Lou C]

Re: No cooling in reverse.

That's why I asked the question a few posts back. Judging by the waterline on the pontoons and the drive, the water level is lower than the impeller. On my boat the drive is fully submerged when it's down and the water level is just below the 'OMC' on the transom mount. So I think for it to prime everything on the raw water side has to be perfect.
On the water muffs you got water pressure to help you. Do the water test in the water.

 

[Jayomc]

Re: No cooling in reverse.

 

[Jayomc]

Re: No cooling in reverse.

So i have water flowing everywhere with no obstruction that i can see.
I have a small slow drip from the impeller housing, should i use silicone on this?
I did not get it in the lake today and its weather permitting for the next two day.
It looks like the impeller is not doing its job but all it has to do is spin.

 

[Lou C]

Re: No cooling in reverse.

You have some kind of debris in the water intakes get nice bright LED flashlight and look in there, I could see it behind the plastic water screen.
There should be no drip at all from the impeller housing. You may need to replace that gasket and you should also use OMC gasket sealer on it.

Water flow tests look good. Are you using an OMC impeller or an aftermarket?
Here is another little tidbit, you supposedly can't mix OE impellers with aftermarket impeller housings or vice versa,the size of them is a bit different. IF you are using aftermarket, try replacing the whole impeller, housing, cage, wear plate with the OE stuff.