Temp Gauge or real problem???

[imported_scott_m]

Hi again iBoats and Happy Easter. I need some help thinking this through. I've got a 1990 Merc 135 2.5L V6 on a 1990 21 Sea Ray Laguna. I've had this boat about a year now, and think I either have a chronic overheating problem, or a gauge that is not reading right. About 6 months ago she started running warm, so not knowing the maintenance history on the boat I had the impeller changed. I also pulled the thermostats out of both heads (South FL). It seemed to be OK for a while, then about a month ago started getting hot again. So out of the water it came and in to the shop. This time, the shop (different, the boat was in GA when I had it done the first time) did a rebuild on the water pump as well as serviced lower unit. I got the boat back in the water 3 weeks ago. I ran it hard from the ramp back to the house and all was fine. Yesterday had the boat out idling around and it was fine, but then when I throttled up she shot up to 210 or so. Interestingly, last time it was overheating, I could put it in neutral and raise the RPM to 2500 or so to get it to cool down. That did not work yesterday, although just riding at idle speed would drop it down. Anyway, yesterday I felt the water coming out of the pee stream, and it was almost hot enough to burn your hand, although I would not say it was anywhere over say 150. Also, when I got back to the dock, I pulled the cowl and felt the heads and block and nothing seemed warmer than it should be. Also the pee stream is strong and there is water coming out of the ports. I'm wondering if I can put a DVM on the signal wire for the temp gauge to see if it is a problem with the gauge, sender, or wiring? Or is there any other way to determine flow through the motor? I have not checked the timing recently, but I think if the timing was so out of whack to make it run hot that it would not run well (performance is excellent right now).<br /><br />Sorry for the long post, but I'm out of ideas, and although I've done a lot to get ready for the spring king run (plugs, lower unit, water pump, carbs, decarbon the motor, etc.) here I sit with 71 degree sea temps, kingfish off shore and I'm tied to the dock. Look forward to your insight.<br /><br />Scott

 

[robalofish]

Re: Temp Gauge or real problem???

Happy Bunny Day,<br /><br />1) I'll get lots of feedback on this BUT ---Put new thermostats back in. They make the water flow correctly.<br /><br />2) Check the poppet valve - it may be sticking. Located lower Stbd side near the switch boxes on mine. (94-200hp).<br /><br />Also : water on the Indicator stream comes out after the thermostats so it will be warm. If you want catch in styro cup and measure (with thermostats it shoud be 140 deg.).

 

[imported_scott_m]

Re: Temp Gauge or real problem???

I read a couple of other messages on the poppet and that does sound like it may be the problem. I also noticed yesterday when I had the cowl off that there was some water down around the bottom of the block, so that may indicate the telltale is working for the poppet. I have to go out of town this week, but should know more by Friday.

 

[imported_scott_m]

Re: Temp Gauge or real problem???

Thanks again to iBoats! Looks like the poppet valve took care of the problem. I also rebuilt the fuel pump while I had the boat out of the water. Temps now do not exceed 145 WOT, and with the fuel pump rebuild, idle is a little smoother, and I may be getting 100-200 RPM more on top end (5,700 OK for this motor)?<br /><br />Kingfish Beware!

 

[achris]

Re: Temp Gauge or real problem???

5,700 is just fine.... <br /><br />Have fun.....<br /><br />Chris............

 

[gss036]

Re: Temp Gauge or real problem???

Scott, what parts did you have to change, is there a kit for the rebuild?

 

[imported_scott_m]

Re: Temp Gauge or real problem???

Hi Gary. Funny thing about the "parts kit", my wife went to our local Mercury parts place in St. Pete. Real nice bunch of folks there. Anyway, she asked for the "kit" (per my instructions), but they gave her the right parts. Basically all that is needed is the new diaphram, two gaskets for the valve housing, and a rubber grommet (although I've yet to figure out where the grommet goes). I think the total for parts was about 18 bucks. The fuel pump rebuild did come in kit form and was about 10 bucks.<br /><br />I had tried to make the repair in the water last Friday, but could not get comfortable working at the position the motor was in, so I hauled out. The poppet (at least on my 1990 135) is on the lower starboard side of the motor behind all the ignition box stuff. I had to take the bolts free for the box, then undo most of the wiring connections. Then I tied the box out of the way and could get to the poppet. It's 8 shaped and held on by 4 half inch bolts, and has a water line coming out of it. I'm not sure if my diaphram was bad (although it was MUCH more flexible than the new one), or if it was just all the salt/corrosion/accumulated gunk up in the housing that was keeping it from working. BTW, Vineager works great to clean the salt out.<br /><br />Hope this helps.<br /><br />Scott

 

[robalofish]

Re: Temp Gauge or real problem???

Scott,<br /><br />Right about the kit, there isn't one but you can look up all the numbers on Mercurys parts site then you can call to be sure they have them.<br /><br />The rubber grommet goes inside the opening, the old grommet peels out and the new one will slip into a plastic carrier. The grommet is what the poppet valve rides on. You should be able to peel old one out with your finger. Also your old one might be gone. Also I found it easiest to change by dropping the lower cowling pan, only about 5 bolts.

 

[gss036]

Re: Temp Gauge or real problem???

What about the valve itself and the spring, don't you replace those? I think I've done most of the other small things, thought I'd do this also since the boat is out of the water for a couple of months.

 

[imported_scott_m]

Re: Temp Gauge or real problem???

The diaphram is basically the valve. There is a metal plate that goes under the diaphram, then there is a plastic disc that sits on top and is held to the "plunger" with a small screw. My spring had some light corrosion on it, but I was able to soak it in vinegar and it cleaned up fine. Other than that, it's just two gaskets...one between the outer housing, and the other goes between the inner housing and the block. Other than that, I don't think there are any other parts. Oh yeah, the bolts were a little corroded as well, so soak them too if yours are. Hope you find this helpful.

 

[gss036]

Re: Temp Gauge or real problem???

RobaloFish, You say it is easier to drop the lower cowling, wow! I looked at my 1889 200 Merc engine sr#OC139752 this afternoon. I just could not see how that would be done. My lower cowling 1/2s are connected to 4 large motor mounts and no nuts (pins) to remove them. I looked at one Merc manual, but cannot find one for my engine, it was not the same as my engine, the one I saw for a 135-150-175-200 Merc. I think the poppet valve could be changed w/o dropping the cowlng but would really be easier if that could happen. Any help would be appreciated.

 

[gss036]

Re: Temp Gauge or real problem???

^ bump. looking for some help here.

 

[imported_scott_m]

Re: Temp Gauge or real problem???

I'm not sure about your 200, but on mine, all I had to do was take 3 bolts out and disconnect both the heavy battery cables going to the solenoid, then undo all the wiring for the trim pump, and I could lift the electronics box out of the way. I just used a wire tie to tie it off to the side and I had good access to get a ratchet in for the poppet valve.

 

[gss036]

Re: Temp Gauge or real problem???

Scott, I looked at that possibility. I am thinking that would be easier than droping the lower cowling, unless I am missing something. I think it could be done without moving the electronics box out of the way. It would be tight though. I have a lot of wires in that area as my wiring harness plug shorted out and the engine is now wired direct w/o the plug. I could not see $500.00 for a new harness. <br />I am in the process of redoing my depth sounders (bought a new eagle) and installing a new tranducer and speed wheel. One project at a time for now.