1985 2.4L 175 - Poppet Assembly

[paradak]

520492520493520494520495Greetings all.

I have a 1985 Mercury 175 with the older poppet assembly (no hose). I do not see an indication of the poppet opening up during acceleration on the water pressure gauge. The engine has not overheated but runs a little hotter at 3500rpm than I would like (about 170 on the temp gauge). Pressure at 3500 is 22PSI and about 7PSI at idle. I have previously replaced the poppet components and the water pump impeller is fairly new. The assembly of the poppet was in accordance with the diagram below from marineengine.com and looks like the Seal Location B picture (i.e. seal on the block side of the plastic valve.

After thinking and researching, I find examples of replacement parts that have the rubber seal behind the plastic valve (away from the block) and under the spring as shown in Seal Location A picture and in the image for the replacement kit 8MM0114707.

If there are any folks out there who have first hand knowledge of proper positioning of the rubber seal I would appreciate it. I think I have installed it wrong and thus am limiting the water flow above 2000 RPM.

[tlwjkw]

thats a bushing tha drives into tha block, taper towards tha inside... then its "staked" to tha block three or four times around tha edge.............. they usually don't come out unless its driven out from tha inside.. if tha old one came out easily then it wasn't installed properly ta start with........

[transomstand]

Ok, starting from the beginning, there are 3 poppet designs. You have the second design.

Next, the terminology of the parts is sometimes confusing, even Merc will change names from year to year.

What you're showing in the photos in different positions is the poppet seat (#15), it's made of hard plastic and it is ALWAYS attached to the block, then staked in place with a punch to squish the aluminum around it and hold it firmly in place.

What is missing from your photos is the grommet (#16) to seal the valve. The white valve uses a rubber slotted grommet on it's flange to seal against the plastic seat when closed, so your poppet won't seal completely.

Always remember parts photos are for the purpose of identification only, might not be exact, and should not be used as an assembly guide.

And finally, you're chasing a problem that really doesn't exist with your temps. A max of 170 is perfectly fine for that motor. My experience running motors with 2nd design poppets would indicate they run a little toward the hot side anyway.

Any time you suspect a temp issue, always confirm with a heat gun cause them cheap dash gauges can have up to a 15% error.

[transomstand]

thats a bushing tha drives into tha block, taper towards tha inside... then its "staked" to tha block three or four times around tha edge.............. they usually don't come out unless its driven out from tha inside.. if tha old one came out easily then it wasn't installed properly ta start with........

Damn, I gotta learn to type faster:D:D

[paradak]

Thank you TLWJKW, When I originally pulled the poppet apart, the poppet seat came out easily. I appreciate your response.

[paradak]

Thank you tansomstand, Your knowledge is invaluable and I appreciate you taking the time to respond so completely. I have already checked the accuracy of the dash temperature gauge with an IR Gun on the heads near each cylinder. The temp gun indicated +10 degrees compared to the gauge at idle. I will ensure the rubber slotted grommet is in place on the engine and stake the poppet seat.

The pictures I posted were of the old parts taken out of the engine. I recently rebuilt the motor last season but only have about 3-4 running hours on it so I am watching everything closely of course.

In the lake, temperature on the gauge while idling for extended periods is right at 150 degrees (standard 143 degree thermostats). At 3500-4000 RPM is where the temp creeped up to an estimated 170 degrees but did seem to stabilize there. After the higher RPM, return to idle and the temp goes back down to 150. Does this track your experience with these engines?

[transomstand]

In the lake, temperature on the gauge while idling for extended periods is right at 150 degrees (standard 143 degree thermostats). At 3500-4000 RPM is where the temp creeped up to an estimated 170 degrees but did seem to stabilize there. After the higher RPM, return to idle and the temp goes back down to 150. Does this track your experience with these engines?

That's the kind of thing I've seen. Get your poppet squared away and see how it acts. With a loose seat it was probably leaking but could have been jammed so it wouldn't fully open. You can normally "see" the poppet open at about 1800 rpm or so with a pronounced drop in water pressure, then increase again as the rpm goes up.

What's the temp of the lake water you're running in out there?

[paradak]

Thank you again,

That is my plan, get the poppet to operate normally and watch for it opening. I could clearly see the water pressure drop on my previous 1991 2.0L Merc 150 at around 1700 RPM. Have not seen that with this engine (yet).

Water Temp is probably about 78 degrees on Lake Mead.

[transomstand]

Thank you again,

That is my plan, get the poppet to operate normally and watch for it opening. I could clearly see the water pressure drop on my previous 1991 2.0L Merc 150 at around 1700 RPM. Have not seen that with this engine (yet).

Water Temp is probably about 78 degrees on Lake Mead.

Yea, lake water is on the warm side (we see a lot of 60 degree water out here, only gets warm in mid summer) so that contributes to higher engine temp as well.

As a broad generalization, the faster you dump water from the powerhead the cooler it will get, so if you get the poppet dumping water better it should cool down a little. Let us know how you make out.

[paradak]

Pulled the poppet valve apart this morning and sure enough, I installed it incorrectly. Seat was not set into the block. My bad. Once disassembled the 4 staking marks are clearly visible. When I originally pulled it apart on this engine the seat came out easily so I don't think it was installed properly when I acquired the boat. I can see that with the seat just resting against the block, the spring pressure would not allow it to open at all. I was able to seat the seat (no pun) with a socket and a hammer. It is in there very solid without having to re-stake I believe.

Will likely lake test it in the next 2-3 days and will report back on poppet operation and temps but I am confident it will function properly now.

Thanks again to all for your help.
520572520573

[paradak]

Lake tested the boat this morning. Poppet opens as it should and I can watch the abrupt pressure drop during acceleration. Pressure is in the 10-15 PSI range depending on RPM (10PSI at 3000RPM vs previously 20 PSI at 3K and up to 25PSI at higher RPM). This is right in the range I expected and hoped for. Temperature at 3000 RPM and above is 153 degrees and solid as a rock (with about 80 degree water temperature).

Thanks again for your help Transomstand and TLWJKW.