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Water temperature gauge or water pressure gauge?

I’d go for temp…have them in most cars, never seen a pressure gauge. Looking at the pee tubes, there isn’t much pressure put out by a flexible rubber impeller. You’d need a gauge that showed something like 0-10 psi, over a large swing of the needle
The other issue,where would you mount the sender? You’d have to study the water flow schematic & figure out where water is leaving the engine.
my old legacy 2-stroke Seadoo has temp sender mounted in the middle of the head, there is a boss, cast into the head for that purpose.
 
I agree with adding temperature gauge. Typically, if a marine engine detects an overheat situation, it will shut down and will not restart until the temperature is back in an acceptable range.

I added one for each manifold water jacket of my Honda BF 225. I'm attaching the procedure I used. Some of the links may be outdated.
 

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On a two-stroke outboard, I'd use a water pressure gauge...most of them have a pipe plug in the block in the water jacket...
 
The OP didn’t state what size of motor he’s thinking of. I was thinking smaller outboards. With a pressure gauge, on smaller motors, if you had a blockage, wouldn’t it still show pressure, regardless of the temperature?
your an experienced tech, I’d be interested in your thoughts as to favouring the pressure gauge. I’m not that smart, (I flew big jets vs becoming a Dr), I’ve learned that listening to people smarter than I saves many beer tokens.
 
I'm sorry, it's a 1998 115 Yamaha (V-4). I'm struggling with overheating if running over 4000 RPM's. As I work to find and fix the problem, I want to be able to keep an eye on things and try not to run it until the alarm sounds. I also wat to make sure that it is actually running hot and not just a bad sensor.
Thanks for all your advice guys. My wife actually loves the slower ride! She can hear the bluetooth speakers, and it's nice that the ride is smooth and we have "a chance to talk to each other"!
Yeah, I've got to get this fixed so I can run wide open!
I love my wife, but after 38 years of marriage, I think I've heard everything I need to hear, right? I'm just anxious to get to whatever little island I'm meeting our kids and grandkids on and have some fun in the sun!
 
Ed - if you are oloking for my feedback, my two cents are actually based on your philosophy....the Merc Master Mechanic that taught me always put the water pressure gauge in the high end bass boats we sold...He always said you will see the pressure gauge drop when there is a cooling water delivery problem...long before the overheat warning horn will go off....

that was a little while ago...technology has changed and we have to evolve...the good part is physics hasn't changed...so I think the rationale still applies.

to the OP, I don't think either gauge will help you solve your problem...once its resolve and you baseline how the gauge woks, I think a pressure gauge will tell you when something has changed...
 
Gotcha. I'm not looking for this to solve the problem or probably even help diagnose it. I just feel that by the time the alarm sounds, it's already causing damage. Obviously, I can try lots of stuff in my driveway, but can't actually "see" the results of what I try. But the gauge might help me see if my work has accomplished anything, and at least help me to know when my cooling system is not working and help me to take it easy and not get to the point where the alarm sounds.
Hope that makes sense. I'll continue to use the boat and if it means cruising around at 25 MPH, I can live with that until I figure out what it needs. I'm ordering an OEM water pump now and thinking maybe the after market part that I order is simply just garbage. That would be great if it solves the problem! I'm alsolooking at a blown up picture of the water pump and all it's components and there are some washers that are supposed to go on top of the impeller before the cover bergoes on, and I honestly don't remember seeing those parts in the waterpump kit and I don't remember installing them either. They don't seem to be included in any water pump kit I'm seeing, so they may be parts that I was supposed to reuse, but I dont remember installing them. So, if they help to seal the pump, I may be having some "blow by" issues at High RPM's. Which would show up immediately with a water pressure gauge, but not so much with a temperature gauge, right? You guys are pretty smart!!
I've got some real Sherlock Holmes type of detectives helping me out here!
Thanks for all your input!!
 
makomark said:
Ed - if you are oloking for my feedback, my two cents are actually based on your philosophy....the Merc Master Mechanic that taught me always put the water pressure gauge in the high end bass boats we sold...He always said you will see the pressure gauge drop when there is a cooling water delivery problem...long before the overheat warning horn will go off....

that was a little while ago...technology has changed and we have to evolve...the good part is physics hasn't changed...so I think the rationale still applies.

to the OP, I don't think either gauge will help you solve your problem...once its resolve and you baseline how the gauge woks, I think a pressure gauge will tell you when something has changed...
Click to expand...
Thank you for that.
 
I have little experience with 2-strokes, so I will defer to Makomark on that issue.

However, I do know these big 4-stroke Honda’s quite well, so let me walk you through my rationale for installing temperature gauge(s) instead of water pressure gauge(s.)

As in all outboards, the water pump is driven by the drive shaft, so at varying speeds, the water pump produces a varying amount of water into the block and heads. That pressure is moderated by the thermostats. On my BF 225, the t-stats begin to open at 140 F and are fully open (3 mm) at 160 F. On start up and prior to the t-stats opening, cooling water bypasses the t-stats into a pressure relief valve which, with sufficient pressure opens and dumps the cooling water into the exhaust manifolds. Even when the engine is heated up, at high RPM’s, the pressure relief valves may be activated because the 3 mm opening of the t-stats will allow more water pressure to build in the block and heads. So, where do you install a water pressure sensor? The only logical places are the block, the head, or just before the t-stats. In many cases that will involve drilling and tapping a hole where one doesn’t already exist. And as described, the pressure will likely vary depending on engine RPM’s, T-stat opening, and pressure relief valve activation.

My BF 225 (and most other larger 4-stroke outboards) have temperature sensors in the block and each manifold water jacket. If any one of them is activated, the engine will shut down completely after 20 seconds and will not restart until the temperature is back in normal range, which often takes a long time and may be a long way from home port. So, I want some warning before that happens. An extra bonus is that I can continuously monitor my engine heat, establish norms, and know when it’s time to change out the water pump or impeller before it gets bad enough to trigger the Honda overheat alarm and shut down. These “contact” heat sensors are easy to install and can be installed on the manifolds and/or block as described in my previous post.
 
My alarm goes off, but it doesn't kill the motor. I throttle down and put it in neutral. After idling for less than a minute, alarm goes away, and I'm ready to take off again. I know that I can run at 3900 RPM's all day long without issues, but over 4000 RPM's, it runs hot after a couple of minutes.
 
Well, my youngest son described my overheating issues with his father-in-law, who is a Yamaha Master Tech, and known for being "the guy" to go to for Yamaha issues. He heard my son describe the problems I'm having and said, "Sounds like he needs to replace his water pump to me." That was pretty frustrating after I spent the winter working on resolving the problem. I relaced the water pump, ran descaling solution through it, checked thermostats in a pot of water on the stove, repaced poppett, and finally removed the exhaust cover and cylinder heads to clean all the crud out of the water jackets. BUT, just for fun, I removed the lower unit just for fun and the impeller is TOASTED!! I Replaced the water pump before I ran a lot of descaling solutions through it. AND, I purchased and aftermarket Non-OEM water pump! The impeller is all gummy and soft and deteriorated. I've never seen an entire stainless insert that the impeller fits in that is completely black and coated with gummy rubber stuff. I have no idea what happened to this impeller, but I'm guessing that some of chemicals that I poured into a big drum to run my motor in just ate up the impeller. Pics attached.
 

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Someone on another forum asked if I had a live well and if it had a plug in the bottom. He said he had a similar problem and all logical fixes didn't work. Somehow he figured out that the through hull overflow for his live well, at a certian speed was sucking air through the overflow and causing a cavitation issue between the transom and the the water pickup on the lower unit. I can actually see that happening. My live well is under a set at the back of the boat. I don't have a plug in the bottom. I store and anchor in there and the lid doesn't close completely because of the anchor rope coming out of the live well and under the lid. I can picture how that could happen. I never run the motor without either being in the water or on muffs.
 
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