I replaced the impeller on my 1500. Got it outside and on the hose, started up easy. But, very little water from the telltale. Water pressure gauge reading 0. I took the tube off the head, and there was flow, but weak. So I took it back inside, pulled the lower, removed the pump and impeller and reinstalled. Pulled it out today, and same result.
Any ideas where I need to fix it? could I have the arms reversed? could it have missed the tube (twice?)?
It is best to put the beast in a 55 gallon barrel of water.
That eliminates the question of tap water pressure issues.
That water level in the barrel should be at least 6" above the top edge of the lower unit where it contacts the drive shaft housing.
If the beast has been used in salt water much, there is a possibility that salt corrosion has crushed the water delivery tube at its top end.
I have attached a picture of just how powerful salt corrosion is.
Doc- I wish I could use a barrel, but just not really doable where I'm at. The PO put her into salt a couple times (thats why I had to replace the trailer axle) but not much, and flushed after each time.
I used a bigger hose today, same result. I pulled the lower off again, inspected and cleaned, then reinstalled. I was extra certain the the tube lined up.
this time was much more water going through the engine. Im going to pull the fitting off that the tell tale goes to and make sure its clear. With as much water as I see going through, there should be more stream.
Will post results as I find them.
Does your tell tale tube come from a fitting on the spark plug surface ("top cover" in the parts break-down)?
Usually if there is a build up of dry corrosion flakes in the water jackets that subsequently break free and flow until they block up the exit fitting of the tell tale,...You can 'ram rod' a piece of small wire up the fitting while the beast is running, and get the flakes moving out. About 1.5 inches in is adequate.
Another way is to use a blast of compressed air up the exit fitting while the beast is running. This scatters the flakes, and after several 'purges' like this, the tell-tale should show a nice flow.
If not,...Remove the fitting from the top cover, clear the corrosion inside the top cover where the fitting was, and fire the beast off & see if you are getting a good flow there.
Don't let the beast run too long with this fitting removed, but a couple minutes is okay. You don't want the water to escape too freely here and possibly cheat the higher cylinders from their cooling water.
A couple of things come to mind.
First as a side note the water should be mostly escaping from the vents above the cavitation plate not through the exhaust in the prop. The exhaust is mostly dry with water surrounding the tuner rather than inside it to keep temps cool. Wet exhaust robs horsepower so not mixing water and exhaust was benificial, a big change from the earlier 60's Inlines where water and exhaust mixed and dumped through the hub. If lots is coming out of the hub the rubber grommet in the lower unit that seals the exhaust tuner needs to be looked at.
Now looking at possible reasons for what you are seeing:
The simple explaination is not enough water volume is being supplied by the muff hose to build pressure. This has nothing to do with what the pump can do, the pump can't provide anymore volume than is supplied by the hose. Keep in mind water can circulate fine but, unless more water is being supplied in greater volume than escapes no pressure will build. The fact that not much is escaping the muffs means the pump is drawing in the available water fine and it's getting up to the motor because it is running out the bottom, the weak telltail says not enough volume to build pressure. I run pressure gauges on all my motors and I find that the house hose is marginal on volume to build pressure. You will notice no real change in pressure when you go to high idle on muffs because it's the garden hose volume limiting not the pump.
When boat is in water I also find Idle speed pressure is low but, in this case it's not marginal volume (lake is infinite) being supplied, it's pump volume output not high enough at idle to build pressure, motor still has a weak tell tale. In this case reving off idle the pressure and tell tale stream increase as pump output goes up.
As far as things that could be wrong with the assembly of the new impeller, things to look for are the grommets on BOTH ends of the water tube. If one or both are not installed correctly, damaged, missing or the tube not seated a lot of water will discharge right directly into the mid section and run out the bottom, this also Might possibly get a small amount to the block giving a very weak tel tale dribble. So it can be misleading as it appears almost normal but, the motor is not getting anywhere near the water it should.
Also look for cracks on the top pump housing or an enlarged hole where the drive shaft goes in. Often if an old impeller self destructed due to lack of water, the plastic housing starts to melt particularly around the drive shaft hole. If housing warped it may not be sealing the pump gaskets and wear plate fully. Any of these defects greatly reduces pump efficiency hence volume reduction hence low pressure.
My two cents......
When I used the bigger hose, I had water escaping the muffs, so I'm
assuming there was enough supply. There is a lot of water coming out the vents, and only spittle from the exhaust. From the volume coming out of the engine, I'm hoping that its only the tell tale clogged. My pressure gauge also comes off the same fitting.
As Doc said, its a brass fitting next to the spark plug. I won't have a chance to fire up the motor today, but I'll pull the fitting and see what I can see.
So here's the latest. I pulled the plug for the tell tale, and everything looked clear. I then put the lower into a tub of water, and started the engine. I used a small, soft wire to clear the tell tale, and got a stream at idle. A few days ago, I lake tested. started with a stream, no indication on pressure gauge. then idling out, no stream (or rather, very little). at 2500 RPM, I show pressure, but not as much as last season, and not as much as I would like. I kept it a short trip, and didn't run the engine too hard.
In the next couple days, I plan to pull the lower (again) and hook up a hose to the copper pipe, and see what kind of flow. If its flowing good, then I will look further into the pump. If its flowing poorly, I know the lower is fine.
I know its been a while since the last update. I work in the soda bottling business, and this summer has been brutal on the work hours. I only now got a chance to get back into it.
I was (am) working on the basis of, pressure was decent before I fiddled with the impeller, then went bad after my meddling. I changed the impeller when I first got the boat, ran 2 summers, and wanted to replace it as a precaution. This leads me to where I am now.
I ordered and installed an entire pump kit. No improvement. Even tried it in a tub to eliminate the volume issue. Now I want to check where the pipe connects to the powerhead. What is the easiest way to do this? Is there a way to check the pump on the lower when its not installed for water delivery?
"Is there a way to check the pump on the lower when its not installed for water delivery?"
Yes,...Hose clamp a piece of automotive heater hose onto the top of the drive shaft, then hose clamp a socket into the top of this heater hose. Then I have a 1/2" drive extension that I cut off the female end, and secure it into a husky gear reduction 1/2" drill motor.
Install a 17" piece of 1/2" copper tubing into the exit port of the water pump housing.
Completely submerge the water pump housing in your tub, have a pal hold the lower unit firmly, hang on for dear life, and make the drill motor spin the drive shaft (clockwise only).
The water pump should be able to pump water up and out of the 17" copper tube plus at least a 1/2" or more.
"Now I want to check where the pipe connects to the powerhead."
To check to see if the water is freely able to fill and exit the power head,...
I hose clamp a piece of garden hose onto the bottom end of the Merc's copper delivery tube, install a common female garden hose end onto the bottom end of the hose, and connect it to your water hose & faucet.
Turn on the faucet a little bit and wait. If it takes more than 30-45 seconds to start falling out of the mid-housing (drive shaft housing),...Open the faucet a little more & wait again.
You don't want to apply too much water pressure, as it can (and will) push past your water jacket barrier gaskets, and could enter into the combustion chambers.
It should also exit your tell-tail fitting during this exercise.
12 psi should be safe if you have a way to monitor your faucet pressure.
If all this checks out, reassemble and put the beast back in the tub & see how it cools.
The tub needs to be deep enough to completely submerge the water pump housing, and have enough volume for the water to stay cool when the exhaust is doing its best to warm it up.
I leave the water supply to the tub running full blast to aid in keeping the tub water cool.