Really stuck on what I think is an issue with my 1999 Nissan 25hp 2-stroke. This motor is new to me, but started first pull, ran great since I bought it.
Here’s where I am stuck. I cannot get this thing to pee out the telltale consistently while flushing it. Have tried different muffs, put it in a trashcan full of water, everything. Sometimes it does, sometimes it wont and I shut it down right away.
Drop it in the water and it pees right away idling at the ramp. Pees while running no problem, steady stream.
I’m going to flush it with Rydlyme, replace the impeller, and put a new thermostat in it. Tempted to pull the head and get a peak at the water jacket channels, but other than that I’m at a loss for ideas or causes.
Hope the lime stuff works. I have used toilet bowl cleaner to try to clear out salt build-up. My old Merc 2-smoke got cranky about flowing water and the culprit was the plastic sleeve that connected the tube from the water pump to the tube into the power head had partially melted, due to an overheating incident. It reduced the water flow enough that the pee tube wouldn’t flow, but the engine ran cool enough. Took a while to find that. Good luck, TexasJim
Rydlyme has never let me down. That stuff works. Get a cheap pond pump from Harbor Freight, some clear tubing & a bucket. Pull your lower off, then connect your tubing & fill up your bucket. Let it run for several hours. You’ll be amazed (& horrified) at all of the salt & deposits that end up in the bottom of the bucket!
I’ll echo the rydlyme stories. The gunk and trash that came out of my HPDI 200 on an old flats boat was absolutely astounding. I used the pond pump method/clear tube and 5 gallon bucket(s) with a crude filter/straining system and let it run overnight.
Also, when replacing the impeller, I would recommend doing the whole water pump housing, seals, and related components. I can only speak to yamaha and merc, but I typically get the whole “water pump kit” which has all the items you would need. I do this because I had a warped water pump housing years ago that to the naked eye looked fine, but gave me intermittent issues like you are describing. Once I replaced the housing, seals, and bolts, it was good to go.
Thanks for the tips everyone. Going to replace everything and flush. Hoping it’s a combo of restricted flow from years of build up, and some worn components.
My 40 Mariner does the same thing. Pees great at the lake, I’m 90% freshwater use. But I can’t get it to pee at all on muffs, and does ok in a barrel full of water. I’ve changed pumps and run a weedeater cord up into the block. It doesn’t matter if the thermostat is open or closed. So, I’m interested in what you find.
When it is in the water any leaks on the suction side of pump are underwater and it will not suck air and lose pressure. I would make sure the water pump housing seal is seated right. Just a guess, take it for what it’s worth… lol
Have you tried pushing a short piece of weed eater line down the “pee hole”? I’m not optimistic this will help but since it is so easy to try, I would.
Had an old set of one side fed round ones, those worked about 60% of the time. Bought some double side feed rectangle ones, have only used them a couple times, but batting around .500 with them.
A leak or warp in the pump housing makes sense to me, boat in the water there’s enough pressure to push past/equalize any leak or air lock.
Gonna dive into it this week when parts arrive. Will document if I open up the head/exhaust. Not sure how deep I am going to go, but as a guy with ADHD and an internet connection there’s no telling where this will lead.
Another random thing I’ve noticed here at my house, Is garden hose difference.
My front hose is a traditional garden hose, 3/4” rubber deal, nothing fancy. Using the rectangle dual feed muffs, even with the shallow water scoops, mine flushes and pees fine.
My back yard hose is some stainless thing my wife bought. It’s smaller in diameter and noticeably doesn’t have the flow of the front hose. My motor will NOT pee on that hose.
Good to know. Might try a different hose. I put one of those retractable hose reels on the side for ease of washing the boat down, etc. It is a smaller hose than your standard garden hose.
If that works, now I’m in the mindset of do I just do a full service with new parts and know the install date to track it going forward? Probably just because it’s a 25 year old motor and I’d love to treat her right and get plenty more time. It has great compression and starts up with ease and runs great. Would be nice if my kids were running a motor 20 years older than them in the future.
Definitely something to think about. I’m using a standard hose, but I have 100ft plus. If I shortened the run, it could increase the pressure and volume. Thanks for the tip!!
Since its a smaller motor I would run it with the lower unit in a washtub or suitable container filled with water.
Add that flush stuff if you got it.
Add more cool water as needed to keep temp down and maintain level.
I agree with having an issue on the suction side. When submerged, it picks up fine. On the muffs, there is air leaking through somewhere. I have experienced this with mine as well. Works fine when running but can be finicky otherwise.
Update: cut a section of garden hose down to 8’ and hooked it to the muffs. No quick connects, etc. got the motor to pee from the telltale. Picture makes it look like a weak stream but it was solid coming out. Gives me some relief, but I’ll likely still do a Rydlyme flush and put the new parts on that I have so I can track wear and replacement schedule going forward.
Ah, give the poor old thing a break! Pressure is SUPPOSED to be down a bit from the pee hole at a certain age! Seems to me that thing is doing just fine!
Seems to me that thing is doing just fine!