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After reading here many guys change their impeller every year I decided to do the same since it was a used boat but new to me. Before I installed the new impeller the water stream coming from the engine was a bit of a dribble then became a slow not too impressive stream. After we installed the new impeller the water was shooting out with unbelievable stream and flow. Ok so today the engine fired right up but after anchoring and starting the engine again it is back to its old way, a very sad slow slow stream. I dont want to blow my motor. Anyone have suggestions on why it would slow like this? Im thinking of taking it apart again to see whats going on.

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maybe a blockage of the pee stream from the engine, try to disconnect and blow out the pee line...

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Not to alarm you, and I am a huge believer in DIY maintenance but on balance feel that the impeller replacement can be tricky.

Again, in all likelihood all you probably have is some minor debris blocking the pee outlet...a little air or weed whacker line will clear it up.

My worry is that failure to replace an impeller before it breaks up or putting a new one in carelessly could block the water circulation with catastrophic consequences.

Wish yamaha had a screen to protect the water inlet tube between the impeller and the power head

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Ok thanks I will try to clean out pee stream line tuesday. the impeller was replaced by my nephew who is a certified Yamaha tech but he lives in New York and was down visiting when he replaced it.

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I am not familiar with Yamaha cooling systems but is it possible the water flow is simply a function of whether the thermostat is open or not (engine hot or cold)?

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Are we talking about a Yamaha or Suzuki 90? Seanwilmnc not sure about a 1985 Yamy 90 but, my 2007-8 Yamy 90 right from a cold start-up has a strong steady stream from the squirter so I feel that would rule out a flow restriction by the thermostat.

You mentioned having a good flow after impeller change, boat was still at home I assume? You did not mention how was the pressure at the start of your recent boat outting? Later on during that outting you observed a renewed weak water stream from squirter?

Any chance you sucked up sand or silt during the day? With the impeller change did you replace the plastic housing as well? Gaskets/seals where correctly installed,yes? There is a water feed tube that connects to the impeller housing and "plugs" into a port below the power head (through the mid-section). Typically the connection from feed tube to power head is done with nothing more than a rubber type sleeve. If pinched during assembly (cause raising the lower unit into place can sometimes be a real "pita") or now fits loose water pressure may be affected.

Just a few concerns that came to mind from past experiences...check out this web site and review their part diagrams for some posible clues: www.simyamaha.com

Good luck...

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Disconnect the rubber tube from the bottom left side of the block, it is a simple hose clamp. See if you have good stream at the block. If so clean the tube, if not get some fine wire [like bait rigging wire and ream out the block through that lower hole]. I have my second 70 hp Yamaha and also a 1989 90 hp Yamaha and have had to do this many times. It is always clogged with some kind of dried up tiny critters that have crawled in through the pee tube. Sometimes after sitting only a week. If your impeller is coming apart the clog will be rubber parts and even if it clears up I would drop the lower end and check the new impeller.

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Its a 1985 Yamaha 90 hp. I will check all tube connections tomorrow to see whats going on. But when I fired the boat up both after new impeller was installed and yesterday at the dock the flow was strong. Im thinking when i anchored i may have sucked up some sand.

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I went straight from work to the dock and took a water hose and put it right up to the pee tube and blasted it with water. It must have been sand or muck of some sort because when I fired up the motor she was pissin like mad. Thanks for all of the help. This website has been a God send for people like me with no mechanical back round!!!

http://www.flickr.com/photos/45988259...068929091/

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That is possible and if the sand or silt dries out it can block the tube. The 70 hp is the same motor as the 90 hp and my first one was a 1985 bought new. I recently sold it when I replaced it with the same motor. I ran that motor in silt/sand/mud for 25 years and replaced the impeller one time. It was one of the main reasons that I wanted the same motor again, it dealt with conditions that were unavoidable because of the water depth in the creek that had cause all sorts of overheat issues with previous motors. A good trick to see if your water pump and impeller are sucking is to hook muffs to intake, turn hose on low flow and have someone turn over the motor. If the rubber on the muffs sucks in it indicates good suction and the problem is downstream of the pump [water exit points].