Why no temp gauges on O/B?

[FuriousMob]

I see all the basic O/B gauge sets have no temp gauge included. I have an 89 Evinrude 2 stroke V4. The RPM doesn't work on it (neither does the MPH, but I don't really care about that), and I was thinking about just replacing all the gauges with one set, and adding a temp gauge.

So why don't O/B's normally have temp gauges?

 

[Silvertip]

Re: Why no temp gauges on O/B?

Because they have an overheat/oil system warning system. Ever wonder why you hear that audible beeeeeeep when you turn the key on? Oh -- so you don't hear that? If not your warning system isn't working either. And since your engine is oil injected you will never know if the oil injection system has failed because you won't hear that warning either and in very short order your engine is toast. The stream of water that squirts out the side of the motor is called an over-board indicator or tell tale which tells you the water pump is pumping water to cool the engine. However, it does not mean the engine is actually being cooled properly which is why you have an overheat alarm. See how all of that made a full circle? But you can add two gauges (water temp and water pressure) if you wish. Water pressure tells you "how well" the water pump is working. Water temp tells you -- well, that the engine is either overheating, over cooling, or normal. Many people have no idea what gauges are indicating anyway which is why auto makers years ago installed, pardon the expression "idiot lights". Most people know that "red" is bad. But all they know about water temp or oil pressure is that they either have some or they don't.

The tach doesn't work but you aren't worried about that! So how do you know the engine is not overreving or being lugged to death because the wrong prop has been installed. Contrary to popular belief, there is no such thing as a standard prop. Motors don't even come from the factory with one because they have no idea whether the engine will go on a barge, pontoon, race boat, or fishing boat. All take a different style of prop. So fix the tach and make sure your engine revs to 5500 - 5800 rpm at wide open throttle with an average load (what you consider an average load will be for your type of boating).

 

[FuriousMob]

Re: Why no temp gauges on O/B?

Thank you?

I said I don't care about the MPH, not the RPM. I NEED the tach fixed, but I figured I'd look for a set to do the whole thing while I was at it, and while looking noticed they didn't usually come with a temp gauge for O/B's. My boat also did not include one, so it was simple curiosity really, and the "idiot light" explanation makes sense. I've been boating since I've been a kid with my father, so I'm not ignorant of them, but I don't know every little detail about why certain things are the way they are. I grew up with small I/O's and a small yacht, so O/B's are a touch different.

Yes, my engine has an alarm, and it works, but I prefer a gauge because it tips you off before the alarm or shows slight increases which may be minor at the time but can become bigger problems later.

 

[witenite0560]

Re: Why no temp gauges on O/B?

Here's my thought... Outboards have so many different applications, as far as from boat to boat, the temp guage would likely rarely match the rest of the guages in any given boat. Presuming the boat even has guages or a place to install them. A lot of people don't like that, so the manufacturers just decided the idiot light and noise maker would be a more standard configuration.

 

[4JawChuck]

Re: Why no temp gauges on O/B?

I installed a water temp gauge when I installed the water pressure gauge, thought it would be a good idea to keep an eye on the temps at the same time.

In two years I have seen it move from stop pin at 100F and hit 110F...but the water temp that day was 76F. O/B's run so cold a temp gauge is pretty useless.

Water pressure is a far more useful gauge.

 

[witenite0560]

Re: Why no temp gauges on O/B?

Interesting. But, shouldn't a properly functioning thermostat let it get warmer than that? How much water pressure does one run? How do you know how much is too much or too little? Sounds like a good idea.

 

[witenite0560]

Re: Why no temp gauges on O/B?

I checked my manual, 115hp, 1970 Johnson, and it says, using two temp stiks, 125 degree and 163 degree. The 125 should melt, the 163 should not. But, that's applied to the cylinder head, not the coolant. So, not sure how that temp will corellate to the coolant temp. Just info.

 

[jhebert]

Re: Why no temp gauges on O/B?

If you install a temperature gauge on an outboard motor with the sender located at the usually upper cylinder head position, you fill be able to watch the engine temperature--watch it go up and down. It will typically go up while you idle to about 140 to 150-degrees, and go down to less than 100-degrees when you increase engine speed. I have one. It goes up and down all day long, depending on engine speed.

 

[4JawChuck]

Re: Why no temp gauges on O/B?

My sender is in the head near #1 plug, and the motor has a new thermostat mainly because I thought it was shot when I installed the gauge and didn't see it move, it takes a lot of low speed idling around to see any temp rise on my gauge and it has never gone above 110F on a Merc 90hp two stroke...a four stroke is a different animal altogether.

Water temperature has a lot to do with how hot the water in the motor gets, being in Canada the water here does not get much above room temperature even in the middle of summer.

If it wasn't already installed I wouldn't bother with it, the 0-30 psi pressure gauge is what I watch...way more important.

 

[FuriousMob]

Re: Why no temp gauges on O/B?

I guess while I'm at it, I'll install a pressure gauge as well. Thanks for the info, very helpful.

 

[Silvertip]

Re: Why no temp gauges on O/B?

When installing a water pressure gauge it is best to also install a new impeller. Then record the idle, mid range, and wide open throttle pressure readings. Any deviation from these readings down the road will tell you the impeller needs servicing.. If you just install the gauge you have no idea what normal water pressure is for "your" engine. Not every engine will exhibit the same water pressure. Temperature gauges for outboards are very generic and do not require anything special. The senders are 33-240 ohm units and the gauges are typically calibrated from 100 - 240 or so, 60 - 240 or so, or C - N - H (cold, normal, hot). Any of them can be used but the gauge calibrated at 60 degrees on the low end is the most desireable and also the hardest to find.

 

[AguaSki]

Re: Why no temp gauges on O/B?

Pressure Gauge = Tells you what is about to occur.

Temperature Gauge = Tells you what is occurring

Warning Horn = Tells you what just occurred

I like having all 3 systems installed and functioning. You can probably get away with 2 of the 3, but I personally would not operate an outboard without all 3 systems.

 

[Mike Robinson]

Re: Why no temp gauges on O/B?

If you install a temperature gauge on an outboard motor with the sender located at the usually upper cylinder head position, you fill be able to watch the engine temperature--watch it go up and down. It will typically go up while you idle to about 140 to 150-degrees, and go down to less than 100-degrees when you increase engine speed. I have one. It goes up and down all day long, depending on engine speed.

Ditto

 

[john from md]

Re: Why no temp gauges on O/B?

If you have a warning buzzer, it is all you need if you routinely maintain your engine. Impellers don't shred themselves unless they are allowed to run dry or harden from not being changed every couple of years. Open system cooling is not like closed circuit designs where you can loose coolant or have a clogged radiator or heat transfer coil. If you get grass covering your intakes, it happens so fast you will hear the buzzer go off before you notice the gauge at the high end. Pulling the throttle back when you get the buzzer will preclude any damage from occurring from the higher temp. Ingoring the warning or having and inop buzzer will cost big bucks.

As for,thermostats, I have never had to replace one in my boat in 25 years. I check it when I change the impeller but they don't get corroded if the engine is flushed after use and properly maintained.

This info is only for trailered boats. All bets are off for boats that are left in the water all season.

There are enough things to worry about regarding outboard engines. Let's not add to it.

John

 

[jaymasta]

Re: Why no temp gauges on O/B?

Pressure Gauge = Tells you what is about to occur.

Pressure Gauge = Tells you what is about to occur.

Temperature Gauge = Tells you what is occurring

Warning Horn = Tells you what just occurred


I like having all 3 systems installed and functioning. You can probably get away with 2 of the 3, but I personally would not operate an outboard without all 3 systems.

My buzzer warns when engine is getting close to overheating not when its already to late. It also has an Overheat alarm As well as my engine has oil injection it starts beeping intitally when the oil level is low, and gives me near 20 hours of notice before its empty. This tells me what is about to occur if I don't change something, it tells me when something is occuring, and it could tell me what just occured if I were to ignore the previous warnings. And it warns me without having to keep an eye on guages, so I can keep my eye out on the water. I think guages are usefull and good to have, but there is nothing wrong with a properly setup and working warning system that come with most outboard motors, and most of them have steps of warning, not just a loud beep and your engine is gone. I find the warning buzzer or noise much more usefully in typical boating conditions in a smaller craft then guages.

 

[Silvertip]

Re: Why no temp gauges on O/B?

I go back to the auto industry with their use of audible warnings and, pardon the expression, "idiot lights". The same holds true for the marine industry. Many, in fact a large majority of folks would have no clue what normal gauge readings are and would continue to operate the boat with abnormal readings. Addition of the audible warning is what people tend to understand. When an engine overheats people immediately say, but the engine tell tale is flowing just fine. There you go -- the water pump can pump gallons of water through an engine but it can still overheat due to defective stats, bypass (poppet) valves, blown head gaskets, bad ignition timing, etc. So why put gauges on a boat that most people don't know how to interpret. As for the temperature swings, at idle, two strokes need to be warm. Therefore the poppet valve closes and the thermostat controls engine temp. At wide open throttle the engine needs lots of water to stay cool and the stat cannot handle that amount of flow when open so the poppet valve allows that flow. Then there is the voltmeter -- again, most people don't know an amp from a volt so the gauge has no meaning. Then engine fails to start and the dead battery should be a clue that the voltmeter should be watched and understood. Tachometer? Same deal. Trim gauge -- unless you cannot see the engine or outdrive from the helm, this is a meaningless gauge. The seat of your pants and the tach tell you what the best trim setting is. Oil pressure? Here is the grand daddy of misunderstanding. Low oil pressure means we need to add oil huh! Wrong. It means the engine has a bearing issue or impending oil pump failure and it is rarely the oil pump. Anyway -- that's why outboards don't have temp gauges although with the modern EFI/DFI engines with ECU's, that data is now available for display since temp senders are required for proper engine operation.

 

[AguaSki]

Re: Why no temp gauges on O/B?

I can't disagree with Silvertip. There is always going to be a portion of the population that has no clue what their gauges are telling them. For them buzzers and idiot lights are the way to go. Likewise there is also going to be a portion of the population that does understand their gauges, and they want the ability to monitor as many systems as possible. The buzzer is probably sufficient for most, but I will always want as many gauges as possible. I wish I had a bigger dash so that I could add more gauges. My needs may be overkill, but the performance information from the gauges is what helps me to feel comfortable on the water.

 

[john from md]

Re: Why no temp gauges on O/B?

I'd like to take a look at this from another perspective.

Boating is similar to flying as you need to see and avoid other craft while you are operating yours. Lakes and bays have more and more boats running around and too many of them are meeting each other.

In the aviation field, even the most basic pilot is trained in see and avoid techniques and the importance of keeping your eyes out of the cockpit.
Boating does not have a hard and fast training requirement and although some states have implemented basic safety training, there are many loopholes that exempt certain people from taking the course.

Boats are not the only obsticales for other boaters. If your head is down watching an indicator and you hit a rogue wave or swell, your course can be changed 90* in a heartbeat. In some cases, this can result in a swamped boat or ejected occupants.

When running my boat, I cruise by rpm mostly as I know what speed I will get for a given sea state. I constanly have my head on a swivel looking at the water and for other craft. My warning systems get tested periodically so I am conifidant they will warn me of impending problems and my hand is always on the helm and throttle in the event i have to make course or power changes. I rarely look at my instruments except to check my heading.

You might think I am operating a large boat but I am not. My current boat is a 16 foot bayliner and it gets operated in one of the busiest bodies of water in the country, the Chesapeake Bay. It doesn't make any difference whether I am operating a 46ft Bertram or a 13ft Carolina Skiff. I want to keep an I out for the things that can hurt me and most of those are not in my boat.

Just some food for thought.

John

 

[barryll]

Re: Why no temp gauges on O/B?

Very good information and explanations from all the above!!!

I installed water temp, water pressure, and a Cylinder Head Temp (on the hot cylinder of course). I installed the CHT because it is much more responsive. I know from experience (nagging overheat problem) that the cylinder head temp indicates an overheat long before the water temp caught up - just my 2 cents worth.

 

[FuriousMob]

Re: Why no temp gauges on O/B?

Lots of good info to take in. I'm going with a cylinder head temp gauge, and a water pressure gauge. Much like in my truck, I'm not going to be staring at the gauges constantly, but having them to check on once in a while adds comfort, and lets you know things are running normal (once you find out what normal is for your boat).

Growing up there were too many occasions where the good times came to an end too quick while out on the water, and since then, I've taken after my old man and take every precaution I can when it comes to boating/vehicles/house. I'm not so much a worry wart like the wife, but take these things very seriously. If I didn't have a temp gauge, I'd constantly wonder if the last time I checked the thermostat and warning alarm, did I put it back together right? Is it going to go off if it does overheat? In dummy lights a bulb could go out, and with the boat, something can stop working the next day after checking if it works. With the temp gauge and water pressure gauges on board, you'll know if it's working and can get back to catching the next big cat.