fred

I took my boat out finally this weekend and after about an hour on it at various RPM's the oil appears to have water in it.....what I changed over the winter was I took off the original rear-riser manifolds and risers (had 3' tailpipes) and put standard Merc center riser manifolds and cast risers with 4" tailpipes, these were on another boat I had and were plumbed with 1" lines going into the risers and the bottom of the manifolds....2 on each bank of each motor, when I asked some board people about how to plumb these with my 2 outlet thermostat housing they said to plug the upper riser inlets for water and just plumb one line into each bottom manifold, to make this work I had to use the riser to manifold gaskets with the 4 slotted holes so the water would pass thru, the only thing I didn't do was to use any sealer....some said to, some said not to, do you think that is the only thing that is wrong with this set-up is that I should have used some sealer? both motors have the milk.....Thanks for any input, Fred

MACDAD260

What gaskets did you use? The best ones are the ones that look like exhaust manifold gaskets. A graphite looking material without the metal ring in the center. I have never had a leak with a new gasket and I do not use sealer. I do always check the flatness of the sealing surface with a flat file when I have them apart. Make sure the surfaces are true and you should be OK. I also torque them to only 30 ft/lbs per the Merc manual.

It sounds like you have a leak and are getting reversion. I know about this first hand due to being cheap and re-using an old gasket. You probably should pull the valve covers. Most likely they will be covered with white slime. If you really want to get all of the water out you should also pull the intake manifold. A lot of water and slime can collect in there. Good Luck.

Doug

jpclear

Merc. has been through a ton of upgrades on those riser gaskets. Get THE VERY LATEST pt. # gaskets from your Merc. dealer (they are graphite and metal) and don't let him sell you old stock. The newest ones work well. Clean the surfaces THROUGHLY and assemble without sealer. Re-torque after warn-up. I'll get you that pt. # if you need it and let me know. Luck! --- Jer

fred

It just seems strange that they are leaking because I checked these for flatness, (ran a file over them) they were on my last boat and were new then....they were the graphite looking ones....maybe I tightend them too much, the oil wasn't real bad, I ran the engines on the hose for around ten minutes and saw nothing.....I will get another set of gaskets and try it again....Fred

fred

Do you have the latest part #......Fred

jpclear

Merc. pt. # 27-863724

fred

jp....are those the riser gaskets with the four slots in them and not the ones with the two slots and two holes?.....Thanks, Fred

jpclear

2 slots - 2 holes. --- Jer

Jersey Tom

Stupid question, but are you sure the manifolds and risers you took off the other boat were good? Another issue is the height of the riser as compared to the exhaust tips. There must be enough difference to make sure they drain fast enough and water is not sucked back into the engine by the cam. If you have room you can use spacer blocks to increase this angle.

fred

I was told to use the 4 slotted ones with my application because of the one water feed line in the bottom of the manifold...I believe they are actually riser spacer gaskets....Fred