'88 OMC 5.0L Cobra - not enough water at the impeller

[danieldi]

When i'm rising the stern and then lowering back in the water, the impeller is not getting enough water to pump it in the system and the engine is naturally overheating. I checked the impeller and is in order. When i've put it all the pieces of the pump back together, i did it under water and the pump being full of water, everything went fine, but as soon as i'm rising the stern, i've got the same problem. Please help me with this!

 

[hondon]

Re: '88 OMC 5.0L Cobra - not enough water at the impeller

You have a vent/primer tube coming off that water pump housing.Make sure it is connected,free of obsructions ,and in good health.

 

[danieldi]

Re: '88 OMC 5.0L Cobra - not enough water at the impeller

Thank you for your reply Hondon. Were it get's in the housing pump, it's connected propertly. On the other hand, the other end of the tube wich is going down in the upper unit is moving at the base. What is the role of this tube? Can you tell me were I could find a good diagram for the stern? I've tried to buy a repair manual from the internet but I didn't succeded.

 

[Boatin Bob]

Re: '88 OMC 5.0L Cobra - not enough water at the impeller

Daniel...try going to this site, it is an online parts catalog, just pick your year and engine size. It has blowups of the drives. If you pick the upper drive you will see the water pump, if you pick the lower drive you will see the rest of the components for the water passage...good luck!<br /><br /> OMC Online Parts Catalog

 

[danieldi]

Re: '88 OMC 5.0L Cobra - not enough water at the impeller

Thanks for the link. It's usefull! Now, what is the purpose for this hose? Vent ... from ventilating I presume, but how would I know if it's good or bad because just looking at it, it seems fine to me.

 

[Boatin Bob]

Re: '88 OMC 5.0L Cobra - not enough water at the impeller

One thing you could try with the boat out of the water would be to put muffs on it (water hose attachment) and take the cover off the water pump and watch the water from the garden hose go through the muffs and up the water passage to the pump. Do this with the drive down (engine not running), then when you see how much water is at the pump slowly raise the drive to the point where you are having the problem and see if the water flow has changed and if it has then see what is causing the restriction.

 

[danieldi]

Re: '88 OMC 5.0L Cobra - not enough water at the impeller

Tanks Boating Bob. I will try something this week-end.