I was at the lake a couple of weeks ago and as I was headed back to the ramp, I looked at my water pressure gauge and it wasn't showing any pressure. Never a problem like that before and it was working fine earlier in the morning. The tale-tale pee stream was still showing a solid stream so I idled it back 2 miles to the ramp with no issues. While at the ramp, I had my son rev the motor up while in idle so I could view it from the rear of the boat and the tale-tale was putting out a really solid stream with additional water coming from the 2 exhaust ports from the back of the motor. Had a chance to look at it today. I removed the fitting on the lower rear starboard side of the motor that the water pressure gauge hose connects to. I disconnected the water tube from the water pressure gauge, then used an air compressor to blow some air thru the line to check for obstructions. It blew out some nasty gunk, lol. I continued till nothing but clean air was coming thru then reconnected the tubing at the engine. I hooked up the engine to water, started it and allowed water to run thru the tube, albeit even at 2000 rpm, it wasn't a strong stream coming out of the tubing under the dash. I was thinking maybe because it wasn't connected to the gauge so less pressure. I connected the tubing back to the gauge, restarted the engine and still no pressure showing up on the gauge. So, at this point, should I assume my gauge is trash and needs to be replaced or could this be water pump related? Any other ideas I need to check out? I'm going to have the water pump replaced regardless since it's been 3 yrs now. Just didn't know if I should start shopping for a gauge too. It's a 1997 225 hp Evinrude Vindicator. I have a feeling finding a similar gauge will be challenging.

First thing first. DON'T ever rev a 2 stroke in neutral unless you want inside parts to become outside parts.

tmd is correct. You can slowly increase RPM, but never "vroom vroom". In my case, I am comfortable with easing up to 2000 RPM, but that's enough with no load.

Gauges are not specific to an engine. For the most part a pitot-actuated water pressure gauge is a water pressure gauge, and it will work with any engine with a similar pressure range. (pitot-gauge means tubing with water in it to a gauge that senses pressure) You might need to look some to find one that matches the other gauge faces, but those are made for years with little change, so not out of the question. A 30 psi gauge is all you need to focus on. Don't get an "electric" water pressure gauge; those have a remote sensor/sender, with the gauge really being a type of voltmeter. With that water tubing, you have a "pitot water pressure gauge".

When you reattach the tubing, it must have water running through it. Any air bubbles can compress and you may get a bogus or no reading. I have not run mine on a water muff in a long time. It is possible that you won't see a measurable reading like that. You may need to run it in the lake for a valid check.

Thanks for the information. We didn't rev it high, I just meant we raised the rpms above idle but not in a fast way. So, there is no question that water should be running thru the line to the gauge while I'm connecting it back up? I was reading some online posts elsewhere that made it sound as though there shouldn't be any water in the line and it should be reading via air pressure which means I hooked it up incorrectly.

the water pick up on front of the engine is likely clogged, use a small drill bit and HAND turn it into the hole to clean it out. they get junk in them and stop up.

water pressure on muffs is pretty much not gonna happen, not enough water moving thru. to check your gauge, turn the compressor down to 15psi and blow into the hose while attached to the gauge, it should read 15psi if not replace gauge.

Small hole in front of lower unit is for the speedometer. Water pressure gauge gets pressure from engine bliock

Air compresses but water does not, hence the reason to avoid air trapped in the pitot tubing. There is a pressure diaphragm in the gauge. If you have air in the line, the water from the engine pushes against a "plug" of air in the line, that air will compress, and you will likely not get a proper reading at the gauge. Hopefully, you have enough tubing to cut an inch off the end because it can get stretched out and not fit tight. You need it snug, and with a cable tie around it behind the bulge in the neck on the gauge fitting. I can't point to any source saying to avoid air trapped in the line, but feel confident I read it in an Evinrude service manual years ago.

You'll typically find the nipple with the tubing on it on the water jacket around the left side cylinder-head.

Thanks again. I found a small length of tubing and hooked it directly to the gauge and put 15 psi of air thru it and the gauged worked fine. So, for now, I'm going to go with the assumption the gunk I originally blew out of the air line (starting at the engine and blowing toward the gauge) is what was causing no reading to show up. I guess I never really thought about anything building up in that line over time but it's been 23 years since it was installed! I reconnected the water line at the engine, put the muffs on the engine and got it started. I let it run until I saw water coming out of the tubing next to the gauge, then slid the water line over the nipple on the back of the gauge, then tightly secured a small wire tie around it. Next up is to take it to the lake and run it around and see if I get pressure. If not, I think I'll replace the complete tubing from the gauge to the engine and probably the gauge too. It might be a week or so before I get a chance to go to the lake but I'll report back on the results just in case someone else has a similar situation. Thanks again everyone.