king cobra drive sucking air

[jboulay]

I just had replaced the impeller. all is good at idle in water but when i plane off it starts sucking air. anybody ever split a king cobra drive? Could it be the intake hose or tube on the pick up? ( the boat has thru hull exhaust so i can see the water stop blowing out on plane)

 

[marinemech1]

Re: king cobra drive sucking air

it could be the water pocket where the water tube goes from lower to upper gearcase<br />there was a warpping issue with this part definitly order a new one if spliting drive

 

[jboulay]

Re: king cobra drive sucking air

Sunday I will be pulling the boat back out of the water. That is a good thing to check, I was thinking maybe the tube split but all in all the drive needs to be split apart. So it has been known for these drives to have a warping issue on the input side of the impeller? And that would make it suck water on plane. Makes sense I will keep you posted.

 

[marinemech1]

Re: king cobra drive sucking air

good luck

 

[jboulay]

Re: king cobra drive sucking air

Well i did not pull the drive yet but i did check to make sure the passages were clear. all water jets are clear but at 3000rpm it stops pumping water in the boat. i also hooked up a garden hose to the first heat exchange (oil cooler boat is raw water cooled) and all ran fine. at 3500rpm water was blowing like mad and never stopped. i also pushed water from inside out and outside in and did not see any leaks anywhere.At first i thought it was when i went on plane that it would suck air but it does it at high rpm on a hose also

 

[Alexo1us]

Re: king cobra drive sucking air

After looking at the parts breakdown for your lower unit and the symptoms I would check the top of the water inlet the cover where it turns into the tube cracks breaks the cover where it mates. <br />Mine did exactly the same thing how I found was to brake it all down again after I confirmed it. when my baby would run at low rpms mine was about 3000 bring her back down to 1000 she would cool down run all day at 2000 above that she would always push the bow down and plane then the rpms go up and so did the temp. Turned out that the exhaust was leaking into water inlet where it joins the cover in the bottom part of my lower unit under the swivel housing. Hope I explained this right..<br />anyway it would run fine until the exhaust builds enough pressure to blow though in to the water passages stopping water flow I Installed clear hoses to help me find the problem the inlet hose stayed full until about 2000 then I started to see bubbles then got worse all the way up to around 3000 then it went dry.<br />this is where I would look since I went all summer and listened to all kinds of it is an OMC they all over heat they crap, but since then she has been nothing but a joy.<br />please give me this spot <br />OMC's work just fine as long as they are fixed RIGHT.....<br />Sorry i just had to<br />Mine doesn’t have the tube but they both could suffer this problem.

 

[jboulay]

Re: king cobra drive sucking air

Thanks for the info. I will keep on posting. Hope this is it! Starting to get warm out.

 

[Striper Blues]

Re: king cobra drive sucking air

J,<br />I lived through a similar experience with a OMC cobra, which has the same basic pickup pump assembly on the outdrive. After much work and I do mean much (outdrive off three times, seals, even some machining, etc) it turned out to be new plastic housing, impeller and plate that fixed the problem. Mine was the same issue, sucking at at rpm's fine on the hose. The pump kit I replaced(including housing) was a new install during a rebuild, so we didn't think it could be the problem. But it was. Before you spend any real time/cash, spend the $40 for a new kit with housing. Here is one on ebay for example...<br /> http://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?ViewItem&rd=1&item=4550182948&category=26455