1996 Mercury 150 EFI (Nitro Series) Water Cooling Question

[Eric Combs]

Hey Guys -



This past weekend I purchased a used 1996 Nitro 884 Savage with a 1996 Mercury 150 EFI, Nitro Series, motor. The boat runs terrific and I was going through my regular maintenance and found something a bit strange.



I took it out on the lake on Sunday to run it around for a bit. I noticed the telltale wasn't very strong at idle and I got a reading of about 3-5psi on my water pressure gauge. I thought it was a bit low but decided to take it for a spin anyway. I gave it some throttle and the water pressure jumped up to around 10PSI. I ended up running it WOT for about 20-30 minutes total and not once received the dreaded 'BEEEEEEP' indicating high engine temperature. Before heading back, after having just started the motor and right after the thermostats opened up and the telltale started 'peeing' again, I stuck my hand back there and it was pretty darn hot... But still, no warning beep (and it does work - it beeps at me when I turn the the key in the ignition).



I was somewhat concerned about it so I went ahead and replaced the water pump impeller - that was a fun job for one person to handle (lol) - but I got it done within about two and a half hours (my first impeller change ever). I started the motor up and it took a bit for the thermostats to open up and for the water to begin coming out of the telltale again - but it was the same as before. I checked my water pressure gauge and it read about 5psi.



Now - here's where the odd part begins. With the muffs on in the driveway, I gave it throttle and the telltale stream got more constant and stronger - the water pressure jumped up to about 10 PSI or so. I gave it a little more throttle (maybe 3500 RPM) and the telltale stream completely stopped. I laid off the throttle and let it go back to idle and after about 30 seconds the stream began flowing again - water pressure read about 5psi. I let it idle for a bit and then tried again - got the same result.



I let it back to idle and watched it for a few minutes. I could see steam coming off the telltale - by no means a giant cloud of steam (which is how I saw one guy describe it on a forum) but enough to be noticeable from about a foot away.



My question: Do I seem to have a problem or is this normal for these 1996 Mercury 150 EFI (V-150EFI) motors? Any help would be greatly appreciated.



Eric

 

[Bob Bourget2]

Couple of things.....

First...good job on tackling the impeller replacement. You'll never know if you don't try. When replacing pump parts, did you replace the whole kit or just the impeller? On many occasions, people do not inspect the housing, wear plate, or base and they are crucial to proper pump operation. I like to use a skim coat of perfect seal on all gasketed surfaces. Torque housing bolts properly. Too much and the plastic housing can warp causing a pressure breach.

Whenever a pump job is performed, you should also address the poppet valve and thermostats. The poppet controls water flow out of the block {pressure}, and the therms control temperature. All are crucial to this motor for proper efficiency.

It is very normal for this series of engine to have a VERY inconsistent tell-tail. Ranging from barely a dribble to a scalding hot steady stream, and anything in between.

Barometer.....no less than 15psi at anything over 5000rpm. If pressures are LOWER, look to stuck open therms, stuck poppet, worn pump. If pressures are HIGHER {not to exceed 23ish}, look to stuck closed therms, or a closed poppet, or a restriction on the adaptor plate outlet.



OH...and one other thing. Just because the motor "beeps" at you...does NOT mean the temp sensor is operating! You are hearing the oil injection module. The sensor is located on the starboard cylinder bank, between cylinder 1 and 3, and has a single beige wire with a blue tracer. Test it by turning the key on, use a test light and ground it......alarm should sound.



EDIT: Ground the wire! :blink: Sorry....

 

[Eric Combs]

Bob - you are awesome. Thank you so much



Water Impeller Replacement: I did replace the entire kit - the wear plate, two gaskets, housing, plastic tube, etc. I made sure that I put on everything I took off -whether it was from the kit I got or the original parts (screws and what not) - nothing was left over.



Water Pressure: I haven't had a chance to run it over 5000 RPM's and seriously monitor the water pressure - yet. I'm going to take it out tonight and see what she does. I'm guessing the muffs can cause inconsistent water flow, too. I was just out in the driveway and it was getting about 5psi at idle and jumped to between 8-10psi when I took it up to 2500rpm or so. I'll report back with what I get tonight on the lake test.



I'll also look into replacing the thermostats and poppet. How difficult are the stats? I've seen videos and how-to's for the poppet and that seems easy (minus getting the lower cowling off.. grr) How about price?



Thanks again!



Eric

 

[Bob Bourget2]

'Stats are easy. One on each cylinder head at the very top, two bolts each. Remove, replace. Should take about 15 minutes. Poppet {rubber diaphram} not costly at all, about 12 bucks plus a few gaskets.....

 

[Eric Combs]

Hey Bob - looking at your edit up at the top - how can I test to make sure the temp sensor is working? I'm not familiar with a test light. Also, I took the cover off and I see two beige wires with blue tracers - they go to the same place and connect to the same bolt.



Thanks!



Eric

 

[Bob Bourget2]

You are looking at the wrong side....stbd side. You can also use a wire with a couple of terminals to "touch".........:blink:

 

[Eric Combs]

Hey Bob -



I was looking on the starboard (right) side of the motor. I didn't see any wires on the other side of the motor, though.



E

 

[Eric Combs]

Also - here's a video I took of the telltale stream - thoughts?



http://www.youtube.com/watch?v=BwtQ_MtW9Bo

 

[Bob Bourget2]

The port side should have two, possibly three beige wires with male / female plugs within about two inches from the sensor. The stbd side {below #1 cylinder} has only one, and it is the temp sensor for the alarm. The port side sensors are for the ecm to read temp for fuel / air ratio control.

 

[Eric Combs]

You were right. I was looking in the wrong spot (right side, wrong spot). I found the wire you're talking about. Should I undo the bolt holding it in and inspect it?

 

[Bob Bourget2]

Yes, you can. The block and mating surface of the sensor should be clean and corrosion free.

 

[Eric Combs]

Cool, thanks



How do I go about testing it, again? What should trip the BEEEEEEEEEP?!



Thanks in advance.



E

 

[Bob Bourget2]

"OH...and one other thing. Just because the motor "beeps" at you...does NOT mean the temp sensor is operating! You are hearing the oil injection module. The sensor is located on the starboard cylinder bank, between cylinder 1 and 3, and has a single beige wire with a blue tracer. Test it by turning the key on, use a test light and touch the hot side of the solenoid...alarm should sound."

 

[Eric Combs]

Hey Bob -



I read that but wasn't sure what you meant - that's why I asked again. I think I've got it now. Thanks a ton for all your help!



Last night I decided to take the boat out on the water. It got 5psi at idle, 10psi at about 2000RPM then it kind of bounced between 18 and 25 at WOT, depending on how high I had the motor tilted. When I turned the pressure went down to 10 or so but as soon as I straightened out it went right back up to the 20's.



With the motor tilted as high as it will go, it didn't seem to be getting enough water because the pressure would drop to 10 - does that mean I've got my jack plate too high out of the water? Easy fix, though -I just didn't tilt the motor up all the way. Half on my gauge is as high as it will tilt in gear and I was able to tilt it up about 3/4 of that and still keep excellent water pressure.



Anyway - I ran it around for a good hour and I absolutely love it. I've got a few more cosmetic things to do to it but as soon as I get those done I'll post a bunch of pics



Thanks again for all of your help!



Eric

 

[Bob Bourget2]

Sounds good! Do not let water pressure fall below 15psi at wot. Either trim down or jack down. Have fun!!

 

[Eric Combs]

Thanks, Bob. I'll probably end up jacking down a bit to make sure I get good pressure all the time. For the time being I'll just make sure to keep trimmed down a bit.