Well, Now I did it!

[airshot]

You should probably adjust the motor in the water with it in gear so there is a bit of a load on it. My old Merc 90 had the infamous Mercury sneeze once warmed up and it took a while to get it adjusted correctly. I think the manual was off by 1/4 turn on the carb screws if I remember.

True, about adjusting in water and most all my factory manuals say to adjust in water while underway !! In my area we have a public ramp with a long canal ride to the big lake, over half mile at idle ( no wake). I have adjusted all my motors for idle speed and mixture adjustment where applicable in this canal ride. Yes it does make a big difference doing it this way !! On muffs or in a barrel are not the best ways to make these critical adjustments.

 

[Douglasdzaster]

True, about adjusting in water and most all my factory manuals say to adjust in water while underway !! In my area we have a public ramp with a long canal ride to the big lake, over half mile at idle ( no wake). I have adjusted all my motors for idle speed and mixture adjustment where applicable in this canal ride. Yes it does make a big difference doing it this way !! On muffs or in a barrel are not the best ways to make these critical adjustments.

That makes more sense than the way I did it. I think I’ll see if I can’t smooth mine out a little more.
Listen to these guys they know their stuff.

 

[LaqueRatt]

Was pretty nice out today, so decided to try the new round muffs. Man, these work so much better than the square ones! Very little leakage. Kind of weird considering the square kind seems to fit inlet shape better. Started her up which takes a bit of throttle on this one and she started peeing right away. Lots of water spilling out the back. The thing that bothers me though is at idle it's not pushing much water. That's not normal is it? Sorry for the dumb question. All motors should move water any time they're running methinx.

 

[airshot]

Idle speed is slower...not as much water being pumped ! I don't see a problem, don't overthink and create one...

 

[MrGiggles]

As I recall the water pressure on those older Mercs is only 1-3 psi at idle. On my 60 it was just enough to budge the needle off of zero on the gauge. You aren't going to see a very strong stream at that pressure, but it should be steady and not a dribble.

 

[Skunked again]

I agree with airshot and Mr giggles.
Take it out and run it. Put it through the paces. An on the water test is the best test.

Plus, your on the water!!!

 

[LaqueRatt]

OK, guess I won't worry about it, but having that motor running and then seeing the water slow to a dribble does not give me the warm fuzzies! This is my first Merc, but pretty sure my OMCs all pee even at idle. I will say though when I rev the Merc a bit the water comes flying out! First time I really noticed the stream had stopped, was when I noticed the muffs had fallen off! Before that I wasn't really paying a whole lot of attention to water flow to be honest. The guy I got it from told me just had a new impeller put in it. Sure hope I didn't screw it up.

 

[jethro]

They all move water when running but some don't indicate until the thermostats open. My Merc 150 takes a good 60-90 seconds before it starts peeing. I change my t-stats every other year just like my impeller.

 

[flatheadsteve]

Last merc I had was a early 90s 25hp and it took untill thermostat would open usually around 30seconds but it varied 15seconds + or -.

 

[thill]

Hang in there.
How far are you from a ramp? Best to test by backing into the water. If the stream is okay, take her for a spin. Put her through her paces. You may be overthinking.

I have found that some Mercury water pumps are sensitive to running without water. If you aren't happy with the water flow, and the motor is new to you, CHANGE THE IMPELLER. They are easy to do on Mercs and it might save you a lot of time and money in the end.

Worst case, you will know how the engine pees with a good impeller, and you will have a spare, if the old one is perfect, and all will be good.

Make sure to lightly grease the impeller with marine grease before installing. Don't gloop the cup full of grease, just wipe a film over all the surfaces to protect against a dry start the first few times.

I've gotten into the habit of changing impellers on any motor I get. For $35 or so, it's worth the peace of mind

 

[airshot]

I like Thills mention of a wipe of grease inside the water pump housing! I use Dow 111 valve lube for other things so I always have it on hand. Heavy duty silicone grease, use for high pressure water valves an rubber components. Perfect for using a small smear inside a water pump install. Also good for the impellor. As Thill mentioned, less is better !!

 

[LaqueRatt]

I could be mistaken, but don't think this motor has a thermostat. Scored a manual on ebay last night so that should help. If not for the fact the PO told me he paid a marina to replace the impeller recently I wouldn't hesitate to change it out. I agree with you guys who say it's cheap insurance. I'm a bit apprehensive to do it for the first time, but the manual will hopefully show how to do it.

 

[Douglasdzaster]

Was pretty nice out today, so decided to try the new round muffs. Man, these work so much better than the square ones! Very little leakage. Kind of weird considering the square kind seems to fit inlet shape better. Started her up which takes a bit of throttle on this one and she started peeing right away. Lots of water spilling out the back. The thing that bothers me though is at idle it's not pushing much water. That's not normal is it? Sorry for the dumb question. All motors should move water any time they're running methinx.

No dumb questions here. If there is trust me I’ve already asked them.
The water flow does slow down along with the engine speed.

 

[Douglasdzaster]

Idle speed is slower...not as much water being pumped ! I don't see a problem, don't overthink and create one...

That’s my job.

 

[Douglasdzaster]

I could be mistaken, but don't think this motor has a thermostat. Scored a manual on ebay last night so that should help. If not for the fact the PO told me he paid a marina to replace the impeller recently I wouldn't hesitate to change it out. I agree with you guys who say it's cheap insurance. I'm a bit apprehensive to do it for the first time, but the manual will hopefully show how to do it.

I may be mistaken but I think they all have thermostats. Mine is a 1992 and it has one. It was the first bolt I broke off when I got it. Come to find out it had the original in it. Easy to change like the impeller is. Your manual will give you more confidence as well as take pictures with your phone as you go to refer back to. Just make sure you have the impeller turned the correct way. That’s probably the most common mistake if any.
Go to a parts site and enter your model and serial number and look at the cooling system it’ll show you where the thermostat is as well.
Like atrshot and thill they’re good. Take it to the water and run it. It’s easy to keep an eye on the tell tail weather idling or WOT.
Good luck. You got this.

 

[LaqueRatt]

So 4 days ago I buy a manual from a guy who lives an hour from here. The manual is now 150 miles further away than where it was shipped from! Good thing I'm not in a hurry, eh? Lows this week are going to be in the 20s so looks like I'm done playing for awhile.