1987 Johnson 150 Gt temp gauge question ??

[MMarshall88]

I have a 1987 Johnson GT outboard motor and I'm looking to add a temp gauge. I'm about to buy a set of faria gauges for my boat as i have restored it. And I've noticed after reading some threads that I can add either a water temp gauge or a cylinder head gauge. But I can't find on my motor to where I can pull out a plug to install a Water temp sender. Some say that there should be a blind hole to install and others I've read says I need to drill and tap a hole. I'm wanting to know if anyone knows where I can do this or should I use a bracket to attach the sender to the head to read the temp. All I'm seeing from the faria gauges is the water temp gauge. One gauge comes with a sender and reads 60-220 degrees and the other comes with no sender and the other reads 100-250 degrees with no sender. I'm really confused as to whether these temp gauges will work against the head on a bracket. They say water temp gauges. I see no where the faria gauges do they offer a cylinder head gauge with sender. I've also read that everyone seems to prefer the sender against the head vs reading the water temp. I'm also installing a water pressure gauge but that is simple to hook up on this motor. I'm really confused on what to do. I know if this will work on the heads, I will install one for each head and install 2 gauges on my boat to read each head. If anyone has any info on this please let me know as I am supposed to purchase the gauges next week when my new dash and toggle switches and wiring are complete. Thanks.

 

[SparkieBoat]

I have a motor with a temp gauge, I have never really paid attention to how it is hooked up, but I will take a look. I will try to let you know tomorrow.

 

[emdsapmgr]

The crossflows did not come with any provision for mounting a temp sender into the water jacket from the factory. Most mount a temp sender so that the tip mounts flush to the face of one of the two heads. A "Z" bracket is needed to hold the sender to the head. Technically, you should have one sender for each head, but I only run one sender on one head. (The hot horn should still notify you of any overheat on either head.) You could mount two senders, then switch between them to drive just one gauge. It will give you an idea of the typical head temp, whether mounted to the face of the head, or whether it's reading water inside the water jacket. That engine will idle at 143 to 150 degrees in the summer. Maybe up to 155 in a warm lake-that's tops. Temps will go down maybe 20 degrees once the boat planes out and the pressure relief valves open. I run a water pressure gauge too. It is hooked direct to the telltale hose barb-I've eliminated the telltale. The water pressure gauge is nice to have, used esp in those situations where pressure monitoring is required-such as when you run an electric jack place in high speed situations.

 

[MMarshall88]

After searching and searching all weekend, I was able to find that faria does offer a cylinder head temp gauge with sender bracket. So I believe that will work. emdsapmgr , I do believe your right. I searched and searched for a spot on my motor to put a threaded sender in for the water temp but could not find none. I would have hated to have a spot drilled and tapped. I think I will go with the cylinder head gauge with sender. I think that maybe my best option. I will more and likely go ahead and by 2 gauges for each side. I have a extra spot on my dash to put the double gauges for that. Also when I install my water pressure gauge, emdsapmgr, you said you just ran the tube right up to the water Jacket where the tailtail comes out ? Did you use a T tube ? If not. I'm assuming that you don't have a stream coming out the motor now. I was told to take a T tube and attach the water pressure line into it and still have my stream come out the motor. Some call it the pisser stream but I don't think that's the correct term for that. Just let me know thanks.

 

[MMarshall88]

I do have the hot horn that I'm assuming works. I had it go off several time last year and I replaced the water pump and stuff and it didn't come back on. The only horn im getting now is from end of last year, I would be running down the lake and I would notice my primer bulb was squeezed down really tight. When it done that , my horn would go off and my engine would start to bog down. It was starving for fuel. That's the only problem I've had out of mine. I replaced a couple of lines and new Johnson primer bulb as well as rhe fuel filter. Haven't got to take it out yet, but I will as soon as I get the gauges and new dash installed back in. That's one reason I want the temp gauge in. So that I can monitor what the heads are doing to be sure and as well as the pressure gauge.

 

[emdsapmgr]

When your engine sucked the primer bulb flat, likely the constant horn was probably due to the fuel vacuum switch, whose job it is to sense high fuel suction-not an overheat. Not unusual for the ball valves in the primer bulb to stick shut, causing he bulb to collapse on itself. Once the fuel suction reaches 7" hg of vacuum that switch turns on the constant (overheat) horn-to prevent internal powerhead damage due to fuel starvation. Hopefully this is not the reason for your abundance of caution regarding the temps in your engine. I'm really cautions about putting a "T" into the water pressure hose line. I always wonder if the gauge pressure will read lower if some of the water is being bled off to the telltale nozzle. The potential that the gauge reading could read low has led me to just connect it direct to the telltale hose barb in the exhaust cover. No telltale. Guess if you have a gauge the telltale is less important.

 

[MMarshall88]

The only thing I would be concerned about stopping the tell tail is , where does that water go? I was assuming that since the water comes out of the motor, once you stopped it and made the water go straight to the pressure gauge, then the water would have to exit somewhere. ? I may be second guessing it or something.

Also for a note on the hot horn , it was going off last year when the bulb was working fine. That was before I changed the water pump/ impeller. After that it never got hot. We used a laser gun to check it a few times running it on a hot day. Reason I wanted the gauges was to have it so I would know if it was getting hot. That's why I also wanted to add the pressure gauge. I heard some say it was ok to add the T tube and some say it Mihht loose pressure Depending on how it was hooked up. I'll only know when I hook it up. If it does , I may eliminate the tell tail like what you done. I'm assuming from some other threads that I read, the pressure is supposed to somewhere around 8-12 psi. Is that right ?

 

[MMarshall88]

hopefully when i changed the primer bulb and fuel filter, it will cure the problem i was having with the fuel starvation. I hope that doesnt lead me to have to replace a vacum switch or the fuel pump which i think is also the vro pump. the oil vro has been done away with when i got it 6 years ago. been mixing the fuel and oil myself. ive seen some pumps new online for like 500$$. would hate to have to dish that out. II guess thats another problem in itself if it cntinues to do it. I wont know unil i get to take it out here soon when my dash and gauges are in.

 

[SparkieBoat]

you should also check to make sure that you do not have an obstruction in your tank pick up or sometimes there is a backflow preventer at the tank connection that can get clogged. Also make sure that your tank air vent is not clogged. I never buy those stupid overpriced VRO pumps, I premix my fuel anyway and use the old style pumps or a low pressure electric pump. (I know that electric pumps are not the safest way to go, but they work great and are cheap, just check your hoses regularly for wear or leaks.) and you can rebuild the fuel pump side of your VRO, but even those rebuild kits are pricey.

 

[Bosunsmate]

hopefully when i changed the primer bulb and fuel filter, it will cure the problem i was having with the fuel starvation. I hope that doesnt lead me to have to replace a vacum switch or the fuel pump which i think is also the vro pump. the oil vro has been done away with when i got it 6 years ago. been mixing the fuel and oil myself. ive seen some pumps new online for like 500$$. would hate to have to dish that out. II guess thats another problem in itself if it cntinues to do it. I wont know unil i get to take it out here soon when my dash and gauges are in.

Non vro pumps are like $100 if you are unlucky

 

[emdsapmgr]

If the fuel pump on that engine has enough suction to collapse a hose bulb and set off the vacuum warning, it's probably functioning ok. Look elsewhere for your problem-such as the restriction items Sparkie mentions.