Mercury 90 water pressure

[mike daniels]

Gents,



On my Nitro 175 sport the, my water pressure reads about 9PSI when the engine is running at about 4200 RPM (40-41MPH). It's not wide open (wife and kids in the boat) and trimmed for a smooth ride. Prop is a 23P SS mercury unlabled prop (not laser, trophy etc).



I noticed my water pressure was steady at 9 PSI. The "taddle tale" stream coming out of the motor was very strong and hitting the water like a laser. I has alsway hear the the PSI should be in the 12 - 14 PSI range. Is the 90 different?



I asked the previous owner when was the last time he changed the impeller and he said never. (year 2000 engine).



Could I have a string stream but low pressure at the same time?





I think I'll change the impeller just due to age. Anyone have a link to a procedure for changing the impeller on the 2000 mercury 90 ELPTO?



thanks

 

[David Sailer]

Mike: I have the same boat, same set up. Since new, my water pressure has always read a little low on the pressure gauge. I have been told, over and over, as long as I have a strong stream comming out the back, I am ok.



If you sit in idle and speed up the motot, water pressure, on the gauge picks up.



I think the same tube that feeds the speedo, also feeds the water pressure gauge, resulting in low readings.



Good Luck

 

[TOMMY RICH]

I think it's fine but, would replace it due to age also.

 

[mike daniels]

How low is a little low?



as low as 9 PSI?

 

[Dan J.]

Positive pressure at idle is good. Gage, if equipped, should read about 2+ lbs. static idle. WOT look for 12+ PSI; not on flush muffs, but in the water. With the age stated I HIGHLY recommend replacing the impeller, if not a complete housing kit. That pump is on borrowed time as exposure out of the water will take almost as much toll as use/abuse. I attached a video link to help. Good luck!



Just an FYI - Your pitot (speedo) and water pressure lines are independent and should never be tee'd.
http://www.youtube.com/watch?v=NtJXv2GqhYM

 

[Berry Lindley]

You are about 7 yrs overdue on that impeller, git r done.

 

[TOMMY RICH]

I do know that the plastic impeller on the 90's are smaller than you think.

My impeller I had replaced year before last by a marina here in Springfield, Ohio did not do the job like they should have. The following Spring I got caught out on Dale Hollow with a faulty pump and had to be towed in. After taking it to Hendricks Creek Boat Dock and them replacing it with a new one...I found out why it was bad.

When the prior marina had installed it, they smacked it with a rubber mallet or something and cracked the nylon inner bushing.

Next time...I'm doing it

 

[mike daniels]

Thanks



The video and others like it are just the ticket. Looks like a pretty straight forward job.



I actually like the other video that has the British sounding fellow better as he showed lubing other splines and gear lugs as well.



I have a impeller kit on the way.



thanks guys.

 

[mike daniels]

Looks like the impeller was the problem. The old one was installed with the fins going any which way and they were pretty worn.



installed the new one in under one hour and put the motor in a bucket. My pressure at idle was 10PSI and the taddle tale was much stronger.



I'll have to get it out on the water to see what it does at WOT but it look pretty good so far.





thanks for all the tips guys.