92 Merc XR6--High water pressure ???

[22R]

My XR6 normally runs 0 psi at idle, 12 psi at 4K and no more than 15 or so at 6K. It is a modified 2.5 Liter motor. Today while my brother was driving we hit a log. When I got back in the seat I noticed that my Pressure was 15psi at 3K and pegging over 30 if I gave it much more. EGT's were normal and Temp gauge was fine too I believe. I am thinking that something has stuck the popit valve closed. I bought some new gaskets and will inspect soon. Just wondering what else it could be. I am unsure if the hitting something had anything to do with it or not. No signs of wood in the pick ups or any damage to boat bottom. Lower unit is a sportmaster. Thanks for any advice. Motor was running great before and after, I just am uneasy about the change. Gauge zeros at idle as well ??????

22R

 

[F2008]

I kind of remember Jay Smith saying higher than normal water pressure in a Merc indicated a restriction someplace. For peace of mind it sure couldn't hurt peeking into all the water pumping system, upper and lower.

 

[22R]

Thats what I am thinking, thanks Don.

22R

 

[Volatile]

Its likely a stuck or plugged poppet valve or some thing stuck under the divider plate. Take the poppet out and run the motor and see if the pressure remains lower.

 

[22R]

Thanks for the reply. I will take the poppet apart and inspect. If it is something under the divider plate how do I clear it ? Does the P/H have to be removed ?

Thanks again
22R

 

[K.Kiser]

Thanks for the reply. I will take the poppet apart and inspect. If it is something under the divider plate how do I clear it ? Does the P/H have to be removed ?

Thanks again
22R

Yep, but still not a big job and most of the stuff can remain hooked up... If You decide to replace the p/h gasket while in there then it will have to be raised high enough to clear the studs and then some wires and hoses may need removed..

 

[bassracr]

dont rule out wood pulp plugging up the holes in your exhaust plate. had the same thing happen myself and had to pull the powerhead . maybe your temps aren't up much because of low lake water temp. ?

 

[22R]

OK, Pulled poppet, cleaned and reinstalled. Blew air and water through all three water outlets( Block top and each lower side -dry stacked) and through poppet cavity, all seems clear. Checked gauge with regulated air and it is ok. Same results motor runs fine but WP is high. I guess pulling the P/H is next. not sure if I want to do it myself or send it to my local mechanic.

Thanks,
22R

 

[Bobalouie]

Pulling the powerhead isnt a big deal, if you are at all mechanically inclined you can do it in around an hour.

 

[Allyfishing]

22R, I had a high water pressure last year when I first hung my fresh rebuild 225 ProMax. It was high at idle 15 and way over 40 at WOT. I received advice (all good) from everyone I could get to listen to my issue and it kept coming back to the poppet.

I removed the heads and blew air and water thru the holes; removed the divider plate and flushed it and nothing. I replaced the heads removed the thermostats and dropped the lower unit and back flushed with the garden hose and caught the water in a buchet and still nothing.

I went back to the poppet again and noticed that the plastic washer that the screw goes thru to install the poppet and spring and diaphram in place was slightly concave. I never had one apart before so I had no idea what all the parts were to look like new. So I ordered every part new even the casing and metal divider and compared them all and that F&%$@!~ plastic washer was the problem!!!!

Reassembled with the new parts and all was good. Chased that problem for about 2 months.

I'm assuming you pulled the impeller apart in the sporty, right? And checked and back flushed the water route thru it?

Just trying to help

 

[Volatile]

Did you try removing the poppet spring, diaphragm etc and running it with just the cover? Thats what I was saying to do. Your pressure will drop to much lower if thats the problem. A correctly working poppet will allow pressure to build to around 10-15psi on the gauge, then you should see it drop as the rpm increase to around 1500-2500 range depending on the motor. You can pull the ex divider WITHOUT pulling the powerhead. I don't think there is anything under the powerhead that could be causing this. You have water coming into the block. Unless the little triangle below the poppet is plugged, there is no reason to pull the powerhead. Its not likely the heads either. Possibly a lot of sand or rocks would cause temporary high pressure and be inside a head or the area around the cylinders, but what you are describing would need to be alot of blockage. The divider area has 4 water entrances with 3 holes each going into the cyl area. You'd have to have a lot of those blocked. My bet is the poppet.

 

[22R]

OK, here it the update. I pulled and inspected the poppet. I thought that I was on to something as it did seem to have some corrosion under the stainless round plate and crud build up in the passages. The flat plastic washer was a bit concave but I would think that it is OK( thanks Craig for the tip). I cleaned it all up and put it back in and when I went and ran it I had the same results. Next I dropped the lower unit and pulled the two inspection covers on it. I backflushed it and it was all clear. Next, I pulled the T' Stats housings and Poppet and backflushed from each T'stat opening. I did flush out 5 pieces of cyprus shards. The last two were decent size to plug a passage way( I will try to post pics????). I also put the poppet back in to pressure out as much crud as possible. I will now reinstall the lower unit and go try it without putting the cowls back on as I will know as soon as I plane if I did any good. If this doesn't work my next step is to pull the divider plate and heads and check for stuff there. I really think that the floater that my brother hit last week is the problem as the issue happened quickly. I really appreciate everyone's input and help. I can't believe that there could be that much more in there from that one log strike ???? If the pics come thru there are two pieces of wood next to a penny for compairsion and a overall shot of my lil' powerplant. Thanks again Guys. I will keep you updated with the results when I get a chance to head back to da'Bayou.

22R

 

[Allyfishing]

Mine was only a "bit" concave too. A "bit" enough to cause my friggn hemorrhoids!! LOL!!! Once replaced the pressure became normal.

I would have to think that with that much wood in there that you found the problem. Unless there is another little bugger in there too.

 

[22R]

Craig,

Can I purchase just the washer from Merc ? I can change that out no problem ?

Thanks for the advice,

22R

 

[Allyfishing]

I purchased all my parts separately from Don Weed, European Marine who is on the 3 liter board over on BBC. Good guy to deal with. I'm sure Lee Sanderson would have them too or be able to get them for you. I think I still have the wrapper that it came in, I'll look tomorrow for the part number. It is genuine Merc part. I kept all that stuff to remind me how much I hate poppet valve assemblies!! LOL!!!

Craig

 

[bassracr]

i had 1 log strike and had the same issues you are having. i pulled the powerhead up off the exhaust plate, and the dump holes the water exits thru the exhaust plate was plugged with wood pulp. these holes are not very big and easily plugged by wood. i'm betting this is where your problem lies.

 

[22R]

i had 1 log strike and had the same issues you are having. i pulled the powerhead up off the exhaust plate, and the dump holes the water exits thru the exhaust plate was plugged with wood pulp. these holes are not very big and easily plugged by wood. i'm betting this is where your problem lies.

Well, I hope that you are wrong, LOL. My plan is to try it and see if the wood I flushed out so far has changed anything. If it is the same, I am going to remove the divider plate and heads and check there, If there is debris I will remove it and put it back together and try it again and if the pressure is still high then I will pull the powerhead. Thanks for the advice and experience to all of you.

22R

 

[Allyfishing]

22R, I looked up the part number and confirmed with the wrapper (genuine Merc parts) that the plastic washer for MY 1996 225 ProMax is part number
12 76451. You may want to double check the numbers for your particular engine by the serial number on this site.

http://www.usboatsupply.com/outboardparts.php

Navigate to the mercury page where you can pull down a list of engines by model and then by serial number, that's how I did mine and Don Weed confirmed.

 

[bassracr]

Well, I hope that you are wrong, LOL. My plan is to try it and see if the wood I flushed out so far has changed anything. If it is the same, I am going to remove the divider plate and heads and check there, If there is debris I will remove it and put it back together and try it again and if the pressure is still high then I will pull the powerhead. Thanks for the advice and experience to all of you.

22R

I hope you put it back in the water and all is well. if you put it in the lake and the water pressure is still high...,if i were in your shoes , i would disconnect the pos. battery cable and pull the powerhead straight up off the exhaust plate NEXT. you can leave most every thing connected . i think this is your path of least resistance to rule out the next item. its easier and quicker than removing both heads, buying new head gaskets , removing the divider plate , re tourqueing everything ,etc. you have ruled out a few simple items and i believe this would be the next logical step. its not a big deal to do it, lift it up about a foot and you can get to everything you need..if you lived closer, i'd come over and help you do it.

 

[22R]

Bassracr,
Thanks for the advice and offer if you were closer. Now, I went run it and the pressure is still high. I figure there is more blockage. I have a local mechanic who told me that 9/10 times the restriction is in the small holes under the divider plate. You seem certain that it is under the powerhead. One of ya'll is right !! If I pull the powerhead what do I lift from ? remove flywheel nut and thread something onto it ? does flywheel have to come off ? The shift linkage and throttle cable connections, do they have to come off ? I guess I am more comfortable pulling the plate and heads but I see your point as well. I am actually more scared off rounding off bolts and thread damage than anything else. I hope that it all comes apart smoothly whichever way I go. I appreciate your time and advice. It's all good experience and learning for sure !!!!

22R