7.5hp running hot??

[jddens]

When I fired up my 1980 merc 7.5 this year I didn't get any water from the pee hole....replaced the thermostat and impeller......now I get a weak stream from the pee hole, volume seems to fluctuate with the thermo maybe but the water is hot....I get no water from the exhaust at the top of the leg....seems to me I used to get a kinda spray out of there.......any ideas or is everything maybe ok.......don't want to seize it up.......thanks in advance.....John

 

[jddens]

Re: 7.5hp running hot??

Anybody???

 

[bktheking]

Re: 7.5hp running hot??

The stream or telltale is before the stat so the stat has nothing to do with the stream pressure. When you had it apart was the impeller missing any veins? Anytime I get poor flow I pull the lower and attach a garden hose with a fitting and a tube and connect it to the tube and backflush the system. Tell us this, when you pulled the lower, did the water tube remain in the powerhead or did it come off with the lower unit?

 

[jddens]

Re: 7.5hp running hot??

Water tube remained in the leg.....should there be water or mist in the exhaust at the top center of the leg?

 

[bktheking]

Re: 7.5hp running hot??

Hard to say , what are you testing in, lake , barrel , muffs?

 

[jddens]

Re: 7.5hp running hot??

Testing in a barrel...

 

[bktheking]

Re: 7.5hp running hot??

Make sure the water is deep enough on the skeg, chances are it's not.

 

[jddens]

Re: 7.5hp running hot??

water level is way above the skeg.......today i removed the thermostat and ran it....no water from pee hole.....put thermo back in and no water from pee hole.....back to the drawing board....tomorrow I'll pull the lower unit and check everything again.....this will be about the 5th time....all looks good and new impeller.......I'll try flushing with a garden hose with the lower unit off....the old impeller looked good....no missing vanes......

 

[bktheking]

Re: 7.5hp running hot??

Try putting just the gearcase in the barrel and spin it with a drill , see if the pump is indeed pumping, sounds like the powerhead may be plugged up or you have crap in the telltale.

 

[fishndirk]

Re: 7.5hp running hot??

I had the exact same motor a couple years ago, had to change the impeller after it went out. The water tube should remain in the lower unit when pulled. Dont worry about water leakage into that area, the lower gear case is sealed from where that water tube is. Your low water pressure could mean a number of things. If the tube from the lower gear case is not forming a good enough seal (it wont be perfect) than when you shut it off the lower unit case will be full of water and leak out of the seam point for a couple minutes. (Your lower unit above the gearcase will fill up with water). That tube from the lower unit is not suppost to be a perfect fit however so check the cover over the cylinders also. Its just a plate that covers the upper water passage and does not seal the cylinders at all. If all this is good, Id say you do have a blockage iether in the impeller pump output or in the entrance to the cylinder head water passages. Was your impeller shreaded when you replaced it?

 

[jddens]

Re: 7.5hp running hot??

The old impeller looked good, went ahead and replaced it. I had this problem before replacing impeller. The plastic short tube that goes into the water pump does come off with the lower unit, the copper looking metal tube it connects to stays in the leg. The short plastic tube slips over the metal tube in the leg but it is a very sloppy fit, not water tight. Is this normal? I try running the lower unit in the bucket with a drill and try to flush everything. I'll get back with the results this evening........Thanks for your help bktheking and fishndirk !!!!!

 

[jddens]

Re: 7.5hp running hot??

Bad to worse....pulled the lower unit today and the leg and area around the water pump is coated with oily water......looks like lower unit fluid is getting in there from some where......haven't torn it down further yet but will this afternoon..............

 

[fishndirk]

Re: 7.5hp running hot??

The fit of the tube is normal. Its got a diagnal cut at the top right? This is so it can slide onto the metal tube in the upper leg easily but theres no clamp or nothin so thats just how it is. If your water pump is running right it wont matter if its a perfect fit (not for that size motor). As long as its a snug fit its good enough, thats why its a semi-rigid tube. If its cracked or fits too loose replace it. Do this, take as many cowlings and covers off as you can and run it in a barrel. If your water pump, impeller and all its gaskets are good than your loosing water pressure somewhere else. You will be able to see water leakage somewhere else. Check the upper water passages around the cylinders. Mine were the original gaskets and after the impeller went out it dried up and fried that gasket. But if your impeller never really fried than id say one of your gaskets or seals just dried up and cracked from old age. As far as the oil above your lower unit thats a seperate issue. Mine had a little when I pulled it to change the impeller. It could iether be exhaust leagake into the hollow area in the leg or leakage around the water pump from the lower unit. Is it light brown creamy, or dark almost black creamy?

 

[fishndirk]

Re: 7.5hp running hot??

One more thing, remember that motor is not going to **** like a race horse when its at an idle. And oh yeah if it is just a trickle, do you see smoke comming out with the trickling water?

 

[jddens]

Re: 7.5hp running hot??

I give up.......ordered a new water pump and will try that. I have blown air through everything, ran the lower unit in a barrel with a drill (pumped water).....can't find anything wrong.....i can't don't see how the pump can pump water UP to the power head the way the pump connects to the leg....way too much slop. like fitting a 1/2 inch pipe to a 1/4 inch pipe.....gonna leak big time. If new pump doesn't fix it I'm going to figure how to seal the pump to leg connection...........

 

[bktheking]

Re: 7.5hp running hot??

If it's too loose going to the pickup you will need to replace the rubber fitting that sits down where it picks water up from the lake. The part # is 26-33613 , I had a 9.8 do this, I ended up making a fitting from a fuel tank fitting from a briggs and stratton lawnmower motor, hey I was in a jam and it worked. If it`s loose going into the powerhead, try wrapping the the tube end that goes into the powerhead with electrical tape to take up the slack (leaving the end open of course) and shove it up inside and retest, if it works then the powerhead will have to come off to replace the fitting (seal).


Seal part number should be: 36556, 26-36556, 2636556

 

[donaldboyer]

Re: 7.5hp running hot??

My 1984 7.5hp has the water pick up on the UNDER side of the anti vent plate just forward of the prop exhaust. I cant run it in a barrely because the exhaust bubbles get drawn into the pump and she gets hot and the tell tale is spluttery. In gear in the lake is no problem as the exhaust is blown rearward.

I am in the process of fashioning a plate to force the bubbles away from the intake so I can run her in a barrel.

Not sure if you 1980 model has the same L/U design as mine or not.

Hope this helps a little!

edit: clarify details

 

[who10]

Re: 7.5hp running hot??

I had a similar problem with my old 1954 Wizard outboard. Turned out I had a bad seal in the lower unit. the water passages were full of grease. I had to blow compressed air up the leg through the exhaust to get the grease to blow completely out. Did this several times until I was satisfied that the grease was removed. Runs cool now.

Also, how's your lower unit gasket? It's not blocking any water passage is it?