Overheating on plane (impeller question)

[Xesvuli420]

Ok, so the boat over heats on plane...

I have replaced the entire impeller housing and pieces (Since I was told this was a yearly maintenance item anyways, figured it couldn't hurt). Not to say this is the overheating problem for sure, but the old one was all kinds of messed up, and not allowing the designed amount of water to pass. However here's what I'm wondering about...

Boat stays cool as long as its sunken in the water, but once on plane, it begins to heat. I have been told that "typically" this means that a connection, or hose, or something that is under water before planeing is sucking air once planed due to the water level dropping as the boat gets on top of the water...

On my old housing, there is a small hole. It looks like it was designed that way, but I'm not sure.

When I got the NEW impeller, housing, and cage, instead of a hole, it has a new piece on it, with a barbed end (See pictures) like for hooking up a line to it. I asked Sierra what this was, and they said it was to visually be able to see the pump is working. If water shoots out, then all is good. Sorry but this answer just doesn't make sense to me for a few reasons...

1. Since it is on the "SUCK" side of the impeller, won't the boat just suck air on plane instead of water (least resistance) if left uncapped, or unplugged, or whatever?

2. if its to be left alone, WHY IS IT BARBED?

We already know that the boat doesn't cool once on plain, could this be a reason? How about the fact that the cage had been turned to the point it was shutting off half of the water passages? weather it fixes it or not, it obviously needed replacing!

P.S. DO I HAVE THE IMPELLER GOING THE RIGHT WAY?

Here are you some pics...

Description and notes (Just in case)
Pic 1 = NEW impeller with Barb'd elbow
Pic 2 = OLD impeller with NO elbow (and small hole)
Pic 3 = Inside view of hole
Pic 4 = See its on the suck side, if air is allowed to enter, wouldn't that throw off the suction?
Pic 5 = NEW vs OLD (notice how the cage on the old has been twisted, and now blocking HALF of the water passages)

Thanks everyone!

 

[Friscoboater]

Re: Overheating on plane (impeller question)

What drive is that?

 

[Xesvuli420]

Re: Overheating on plane (impeller question)

Cobra

 

[Gary H NC]

Re: Overheating on plane (impeller question)

That barbed hose connection is for the impeller to drain.
BUT on many Cobra drives i have worked on had the hose connected and routed down in the lower section of the drive.

See if i can find a diagram.

Just looked at it,It is a vent hose but the OMC parts diagram does show how long it is...looks to be about 6 inches and turns down through a hole in the drive just below the impeller housing.

As far as the over heat problem i would look close at the water hose next to the bellows.They can crack and suck air when on plane.

You can see it here if you go to the parts books and drill down to upper gearcase for OMC Cobra. Part number 14.

http://www.crowleymarine.com/brp_parts/diagrams/30306.cfm

 

[Xesvuli420]

Re: Overheating on plane (impeller question)

That barbed hose connection is for the impeller to drain.
BUT on many Cobra drives i have worked on had the hose connected and routed down in the lower section of the drive.

See if i can find a diagram.

Just looked at it,It is a vent hose but the OMC parts diagram does show how long it is...looks to be about 6 inches and turns down through a hole in the drive just below the impeller housing.

As far as the over heat problem i would look close at the water hose next to the bellows.They can crack and suck air when on plane.

You can see it here if you go to the parts books and drill down to upper gearcase for OMC Cobra. Part number 14.

http://www.crowleymarine.com/brp_parts/diagrams/30306.cfm

Well how about the lack of water being able to pump thru due to the cage being turned 90 degrees?

I took off the rubber hose that runs up from the stern and goes by the bellows to a connector that goes thru the transom, but it appears fine, and as far as I can tell, the connector looks good too.

Thank you for your help

 

[Gary H NC]

Re: Overheating on plane (impeller question)

Is this a new problem that just started after the impeller replacement?
Was the drive pulled off recently?

 

[Xesvuli420]

Re: Overheating on plane (impeller question)

Is this a new problem that just started after the impeller replacement?
Was the drive pulled off recently?

Actually, it first did it as I put the muffs on and unwinterized it. I only run it 5 minutes the day before the debut on the lake.

Once on the lake, that's when I learned it was fine in the water, and would over heat once on top. At first I thought it was a throttle thing (slow throttle, water cools, heavy throttle, overheats) until of course I learned WOT from a stop would cool thus proving it wasn't a rate of water per throttle problem.

BTW beautiful CC, that's the Cadillac of boats if you ask me

 

[Gary H NC]

Re: Overheating on plane (impeller question)

Thanks for the compliment!

I was thinking of the gasket and rubber seal in the water passage if the drive had recently been off...
Somewhere it is sucking air.
The old impeller did not look too worn out in the picture.

Here you can see the o-rings at the end of the water inlet hose,the gasket and water passage seal..part 35

http://www.crowleymarine.com/brp_parts/diagrams/30304.cfm

 

[Xesvuli420]

Re: Overheating on plane (impeller question)

Thanks for the compliment!

I was thinking of the gasket and rubber seal in the water passage if the drive had recently been off...
Somewhere it is sucking air.
The old impeller did not look too worn out in the picture.

Here you can see the o-rings at the end of the water inlet hose,the gasket and water passage seal..part 35

http://www.crowleymarine.com/brp_parts/diagrams/30304.cfm

Funny you should show me that, when I removed the stern, that gasket(O-ring) wasn't there at all, However, it looked like someone used that orangish silicon to make one, but the only thing left was remnants of the silicon. No worries tho, I ordered one to replace it!

P.s. Im in winston, why dont you just come by lol jk

 

[cr2k]

Re: Overheating on plane (impeller question)

The water hose you checked shouldn't be a problem as it is on the Pressure side of the pump. The cage turned is a problem ans you shouild probably get a new housing. The "O" ring needs to be glued in with type M or similar adhesive but no to the point where the adhesive will be between the housing and the sealing surface. Pull the wear plate and clean the surface behind it and replace the gasket and be sure to use some gasket sealing compound or Aviation Permatex to seal it. I have had fits with some cobra drives getting them to work. On one we had to try 3 housings to get on to work. Go figure. For such an easy pump to work on they can be temperamental.

The shaft the impeller goes on turns CCW from the back of the drive.

Next question..Are the plugs still in the side of the upper? The big screw plugs that are (or were) under the Cobra stickers? If not or loose they will leak air. They should never be removed and you have to take the drive off to replace them. They are just casting plugs, screws screwed in to a piece of metal with a rubber gasket on the inside of the drive cavity.

With very rare exception: NEVER remove a phillips head screw or any screw that is or was covered by a decal or emblem.

 

[Gary H NC]

Re: Overheating on plane (impeller question)

The cage will pull out if careful.There should have been a way to look at it and get it aligned.
I always glued mine in place with some gasket sealer.
Good point on using the Permatex aviation sealer on all the gaskets and the rubber seal.
I have always done that and never had a problem.
I also always replaced the wear plate or at least turned it over.You can get 2 uses out of it.New gasket behind it too...

Ugh! 4 am...off to work..

 

[Xesvuli420]

Re: Overheating on plane (impeller question)

The cage will pull out if careful.There should have been a way to look at it and get it aligned.
I always glued mine in place with some gasket sealer.
Good point on using the Permatex aviation sealer on all the gaskets and the rubber seal.
I have always done that and never had a problem.
I also always replaced the wear plate or at least turned it over.You can get 2 uses out of it.New gasket behind it too...

Ugh! 4 am...off to work..

do you think that lack of O-ring gasket you showed me could cause the air leakage, and overheating on plane problem?

Will do as far as the sealer!