cobra drive water pump not priming

[rlgraham]

I own a 1987 5.0 liter cobra drive that has recently developed a heating problem when first put in the water and/or after raising the drive after a few minutes. New pump on good adapter surface, installed per omc book. Pump is not priming upon first start up or after drive has been raised a few minutes. It hits 200 degrees for about 5 minutes than finally starts cooling. Tested at thermostat housing to verify. Vent hose solid and in place, where does "bottom of vent hose attach?? Whats keeping pump from not priming! Any help is greatly appreciated!

 

[cobra 3.0]

Re: cobra drive water pump not priming

I'd look at your bottom intake screen for debris. It should prime if it was installed correctly.<br /><br />That little vent hose off the impeller housing goes into the hole you see in the drive below the impeller.<br /><br /> http://www.sterndrive.info/id26.html

 

[rlgraham]

Re: cobra drive water pump not priming

Thanks Senior Chief for the reply....I'll take a look at the intake screen....although after about 4-5 minutes it does start pumping and cools off to normal temp....My vent hose does go into the lower housing as you suggested. What is it attached to below that?

 

[Boatin Bob]

Re: cobra drive water pump not priming

When you say it starts pumping after 4 or 5 minutes, are just sitting there idling or are you running? The reason I ask is because the pump changes characteristics depending on the RPM's, when idling the impeller vanes actually rub on the pump casing (needs water to lubricate it) but after a certain RPM the pump becomes more like a centrifigal one because the vanes then stretch out on an angle. When idling is when the pump should have the easiest time trying to prime. Is it possible that the pump is leaking, did you use and sealant to put it together?

 

[rlgraham]

Re: cobra drive water pump not priming

Boatin Bob,<br />First of all thanks for your reply.<br />I start out with it idling at the dock for a couple minutes as I load passengers....(I have pulled the hose off the thermostst housing at this time to verify it is not pumping). I then move away from the dock and idle away at a "no wake" speed....within another 3-5 minutes it starts to show the heat problem. It will get up to about 200 degrees on the temp gauge, hold there for 3-4 minutes than cool right down to normal (160-170). Yesterday, before starting I pulled the water inlet hose off the thermostat housing and "manually primed" it by pouring 2-3 bottles of water down the hose. Upon starting it did not exhibit the "over heat" condition that time! Coincidence??? I don't know! I did use new "Johnson-Evinude gasket sealer" on it and initial testing in the drive way showed NO LEAKS!<br />I forgot to check inlet screen yesterday as suggested by Cobra 3.0....It will get checked this weekend. Thanks for your comments. Any other thoughts?

 

[stressfree]

Re: cobra drive water pump not priming

i had the same problem,i changed the outdrive pump and the engine pump,and the thermostat.same problem.went nuts.took off hose from power steering cooler to waterpump and there was something restricting it.when i blew in it it flew out.never saw what was in it.it also could be a hose collaping inside.i pulled my hose off to the pump and started the engine and it pumped good.if ypu dont get water there dont look any further.let me know.

 

[rlgraham]

Re: cobra drive water pump not priming

Thanks Stressfree,<br />I'll pull all the hoses and make sure the're clean with no restrictions....I'll let you know! Thanks!

 

[rlgraham]

Re: cobra drive water pump not priming

Stressfree...you still out there?<br />checked hoses from thermostat housing down to the water tube coming thru the transom shield....all clear. couldn't check hose from transom to gimbal housing but it is solid and looks to be in good shape. I prime the pump manually by pulling hose off thermostat housing and pouring a couple of bottles of water down the hose....replace hose and start engine and NO HEAT problems...@#$%#@@!<br />What am I missing??