steam from my Merc!

[m casey stock]

Hey Guys,

I've got steam coming from my water pump tale tale stream hole. I start the motor and at idle I get a nice stream of water and everything looks good. We can go out and run the motor at a moderate speed (mid twenties) and never get any warning lights or buzzer, I can trim the motor to where there is hardly no rooster tail around the motor sides (not from the prop, I know not to run it that way ) and see a nice strong stream from the tale tale as well. The problem comes when we slow to a medium speed around 12mph or so, in no time at all we loose the stream and start getting steam, lots of it, but still no warning light or buzzer (these two indicators were just checked for proper operation and appeared normal and okay). I was not expecting trouble, so I did not have my laser temp gun with me and have no idea just how hot it was running. We can take it out of gear and bring the rpms up to about 2K and the stream will pick back up and again everything looks normal. At this point we can troll around at about 5 or 6 mph and never show any signs of heat, just a good strong steady stream of water from the tale tale. This is not a new set up for this boat, so I wouldn't think it would have to do with height of motor on the transom and nothing has been changed or modified from the way we ran it last year. Could this just be a sign of a failing water pump impeller? It's a 2001 Merc 150 carberator (salt water addition, if that makes a difference)
Here is a picture of how it is mounted just in case.

 

[GA_Boater]

Re: steam from my Merc!

Casey - When did you change the impeller? Sounds like it's missing some ears or worn down.

 

[blackhawk180]

Re: steam from my Merc!

Casey, do you have any gauges that might help? Water temp? It sure could be the impeller but I'd be checking intake as well for any obstructions/salt buildup.

 

[m casey stock]

Re: steam from my Merc!

Casey - When did you change the impeller? Sounds like it's missing some ears or worn down.

I've never changed the impeller, but I've only had this motor/boat for a little over a year. It had a good stream last year and never showed signs of running hot so I didn't change it even though I didn't know the history, probably should have but I didn't. This was our first outing this year.

 

[GA_Boater]

Re: steam from my Merc!

First thing to change when you lack history or just because. Change the impeller before trying anything else.

 

[m casey stock]

Re: steam from my Merc!

Casey, do you have any gauges that might help? Water temp? It sure could be the impeller but I'd be checking intake as well for any obstructions/salt buildup.

No gauges for temp, just the warning light and buzzer. I do have a laser temp reader I could use to check actual temp. Surely it isn't supposed to be steaming out the tale tale without a solid stream of water regardless, correct? It does seem strange that it will stream good at idle and at higher RPMs and then quit at a mid. RPM. Sounds like checking the intake for obstructions is in order, maybe something that broke loose like a salt build up that you mentioned, blocking the intake at times and not at others?

 

[m casey stock]

Re: steam from my Merc!

First thing to change when you lack history or just because. Change the impeller before trying anything else.

Thanks, that's what I figured.

 

[m casey stock]

Re: steam from my Merc!

Just wanted to give a "final results" update to my problem. Friday morning I installed a new impeller and two new thermostats. The impeller had one torn vain and retained it's curved shape when removed from the housing, so it for sure needed to be replaced. One of the thermostats was an OMC and the other a very old looking Mercury style. The OMC was stuck WAY open, almost looked like it would have to have been forced that way. I don't know if the Mercury worked properly or not because I didn't test it. Didn't matter because it was getting two new ones anyway and my problem would have either been corrected or not regardless. The maintenance took a total of about 2hrs, and that included a trip to the marine store to match up my replacement parts (it seems Merc. had several possible pumps they might have used, which made it safer to just take the old parts with me to compare) so I would rate this as a pretty simple job that any mechanically inclined person should be able to do. The hardest part was pushing the foot back into place while aligning everything and reconnecting the speedometer tube, for this I put wood blocks under the scag and used the hydraulic trim to make the small adjustments up or down as I aligned the guide tube, the shifter rod and the drive shaft, and to hold it close enough to reattach the speedometer tube. I got the lovely wife to work the shifter back and forth to engage to "torx" style coupler and it slid right up. Now for the good news, IT'S FIXED!!! No real surprise giving the condition that the old parts were in. I wasn't ready for the "on again off again" "pee stream" caused by the opening and closing of the thermostats due to the lack of heat generated by the engine being run without a load. I guess I have had a stuck open thermostat on the one side from the beginning, because it's always had a steady stream at idle from the first time I ever started it. We used the boat on the water today for several hours straight ranging from no wake running, to mid speed running most of the day, to all out running as I attempted to race a similar looking boat as ours only to see that it had a four stroke Yamaha 200 mounted to the rear. I felt pretty good about our set up, because the new tech. engine with 50 more hps didn't pull us that much, but I can't take credit. We purchased the boat last year with a blown power head and the SS prop was already installed with the correct pitch and diameter already figured out for best all around use. Anyway, back to the subject matter, No steam at all, just a nice steady stream after the motor warmed up. Thanks for the input and advice guys!

 

[GA_Boater]

Re: steam from my Merc!

:thumb: MCS. Go run her like you stole her. :joyous:

 

[m casey stock]

Re: steam from my Merc!

:thumb: MCS. Go run her like you stole her. :joyous:

LOL, I did that some, but the Wifey gets too nervous at anything over 20mph so my fun is usually short lived