85HP l-drive water pressure problems

[forceboy]

Have had cooling issues for a couple of years with this motor now - took pn's advice and put a pressure gauge on the top of the water jacket (where guys are putting the tell-tales in). With motor at idle and ear muffs on, not getting any pressure at all. Removed gauge and water barely came out of open hole. Pulled foot off and decided to replace complete pump, housing ect. While I have the foot off I figured I would play around a little bit. Took small hose off that goes from leg to bottom of motor and hooked it up to a garden hose. Water comes out of hole on top but very weak - still not enough to even move gauge? If city water pressure at 60 PSI can't get thru, how the heck is the water pump going to? Funny thing is that motor was just completely rebuilt????? I am almost positive there are no obstructions. Does anyone have a water flow chart for an L-drive or a force outboard? Anyone have any crazy ideas? I am quickly running out of patience (haven't got to drive the boat for more than 5 mins at a time for 2 years!)

 

[Jeremy90bay]

Re: 85HP l-drive water pressure problems

There was a post on here last week that said city water with the muffs is not enough preasure for the gage. try putting it in a barrel then the input is completely submrged. hope I could help.

 

[pnwboat]

Re: 85HP l-drive water pressure problems

I'm not familiar with the L-Drive set up, but testing with water hose is probably not the best way to do it.

Having said that, the water in most engines is fed into an adapter plate that the block is bolted to. The water then enters the bottom of the block and is fed directly into the bottom of the exhaust cover. It goes up the exhaust cover then into the Port side of the water jacket that surrounds the cylinders. Based on your testing, I would suspect some blockage to be in the adapter plate area (if your L-Drive has one) or in the exhaust cover area. The gaskets for the exhaust cover and adapter plate must match up with the water passages in order for water to flow.

 

[forceboy]

Re: 85HP l-drive water pressure problems

Thanks for the reply Jeremy, but I bypassed the pump all together. I hooked the water line up directly to the top of the outdrive - no muffs - and still no pressure at the top end of the powerhead. The powerhead was just re-built so I am looking for a flow chart or schematic that shop water flow from pump to powerhead. Either the system is plugged below powerhead or from pump to top of L-drive. Would blowing air thru system help? Will system handle high pressures?

 

[forceboy]

Re: 85HP l-drive water pressure problems

I'm not familiar with the L-Drive set up, but testing with water hose is probably not the best way to do it.

Sorry pn - I guess we were typing at the same time. Yes it does have an adapter plate. I put the gasket in myself - pretty sure I got it right - the boat was overheating before I rebuilt the engine so the chances of the original build and my build both putting in gasket incorrectly are pretty slim. I guess I am going to have to pull the motor again!

 

[pnwboat]

Re: 85HP l-drive water pressure problems

The adapter plate has a water passage through it. Just below the exhaust cover there is a 1 inch square pipe plug that goes into this water passage. You can remove the pipe plug to look inside the water passage to see if there is any blockage, like an old piece of impeller or something. Might be tough to do while the motor is mounted in place though. Might have to take the power head off to check.

 

[Jeremy90bay]

Re: 85HP l-drive water pressure problems

sorry should have payed attn. didnt realize it was an l drive. do you have boat ramp near by to put it in even on the trailer. it would be a much better test than the muffs or hose.

 

[pnwboat]

Re: 85HP l-drive water pressure problems

Found a diagram showing the exhaust cover and adapter plate. The place that I mention on the adapter plate to check has a pipe fitting with a hose instead of a plug. Looks like there are two hoses that come off the adapter plate?? Completely different set up than I've seen. Maybe one of the hoses is hooked up incorrectly?? There's two variations depending on S/N.

http://www.boats.net/parts/search/Merc2/Force
/85%20H.P.%20(1989%20L-DRIVE)/85LD9C/EXHAUST%20SYSTEM/parts.html

http://www.boats.net/parts/search/Merc2/Force/85%20H.P.%20(1989%20L-DRIVE)/85LD9A/EXHAUST%20SYSTEM/parts.html

 

[Leviathan]

Re: 85HP l-drive water pressure problems

I haven't read all the posts, but wouldn't a stuck open thermostat do that?

 

[forceboy]

Re: 85HP l-drive water pressure problems

Thanks pnwboat - exactly what i was looking for. I have a Clymers shop manual, but the cooling system section is about 2 pages long and pretty much only deals with impeller/pump.

I have had a suspicion that the adapter plate has been my problem all along. The water holes in it are quite small - probably plug very easy! Any reason I couldn't bore them out if I take it off again? I guess that means the motor has to come out! I have one more test and then motor comes out.

 

[pnwboat]

Re: 85HP l-drive water pressure problems

I wouldn't enlarge them more than they were originally. Based on the way the hoses are routed, I would suspect that the water outlets on the adapter plate are drilled to a specific size. Of course I'm just guessing, but I don't see any other way to control the flow of water. I would think that most of the water flow would be directed into the bottom of the block. It doesn't appear that the L-Drive exhaust cover is in two pieces like it is on the non-L-Drive applications. Regardless, the water enters the block at the bottom via the adapter plate and is directed to the water jacket in the exhaust cover. It flows up the water jacket in the exhaust cover and enters the top of the block on the left side of the water jacket that surrounds the cylinders. From here it flows down the left side of the cylinder water jacket and up the right side of the water jacket and ends up in the area behind the thermostat where you mounted the pressure gauge. From here it flows through the thermostat (when it opens) down through the water jacket in the head and out of the motor through a water passage at the bottom of the block.

If there is a blockage, I would suspect that it may be in the adapter plate or exhaust cover water jacket. It has to be before the water reaches the thermostat since you had poor flow when you removed the pressure gauge fitting.

If there is no blockage, then I would suspect that too much water is being routed away from the block through those other hoses attached to the adapter plate. The diagram doesn't really show where both of those hoses go so I can't comment as to what their purpose is (other than to cause confusion...LOL!).

 

[forceboy]

Re: 85HP l-drive water pressure problems

OK - my setup is the same as the first pic you posted. The water is pumped up hose #12 into the adapter plate and from there is supposed to flow up into the water jacket. My question is what stops it from flowing thru the adapter plate to hose #11, thru the brass fitting #13 and out the exhaust or out hose #14 (which connects back to the exhaust plate #8 - and back into the lake - the small tube on the left side)? This is a much shorter route so it makes sense to me that this would be the easiest way for the water to flow (and no thermostat)? There seemed to be an awful lot of water coming out of that tube on plate #8 yesterday when I hooked it up to the hose and it came out almost immediately.

 

[pnwboat]

Re: 85HP l-drive water pressure problems

OK I now understand how your system is plumbed. I would tend to agree with you in the fact that more water should be flowing into the block than out of hose 14. I think you've hit upon something here.

One of several things...again this is pure speculation on my part. Any restriction in the adapter plate, which is not likely since you seem to have good flow out of hose 11 but you never know, or in the internal passage in the block that feeds the water jacket in the exhaust cover, or restriction in the water jacket itself in the exhaust cover will force the water to flow out hose 11.

See pictures below for water flow. This a 4 cylinder, but yours should basically be the same. If any of the 3 rubber tubes in picture 5 that divert the water flow has come out of place, it could also cause a restriction.

 

[forceboy]

Re: 85HP l-drive water pressure problems

Thanks again pnwboat - your help is greatly appreciated!

My setup is the same as your pics - if I remember correctly, the hole in the adapter plate that leads over to the exhaust hose is much smaller than the one leading up into the head, so it make sense more would flow up rather than over. BUT... if I had some kind of blockage in between adapter plate and exhaust head it would send more pressure over to exhaust tube. I am thinking now I may be able to get away with just removing exhast manifold. Should give me a clear view of adapter plate (important part anyways) and powerhead. Sounds like a weekend job! I'll post some pics as I go.

 

[pnwboat]

Re: 85HP l-drive water pressure problems

Yes, I would guess that removing the exhaust cover/manifold or whatever it's called would expose most of the suspected areas where you may have blockage. Also you could view water flow into the block with the hose attached while the cover is off. Make sure you do something to prevent water from accidentally entering the exhaust ports that lead into the cylinders.

This will tell you whether the blockage is in the adapter plate, or somewhere after it exits the plate.

If the flow into the block is good, then I'd look at the exhaust cover itself. Look for blockage and verify that the gasket and water passages line up properly. There are a couple of variations on the exhaust cover gaskets. The water flows into the large exhaust cavity in the block, then through the water passages in the exhaust cover over to the thinner exhaust cavity in the block and on to the water jacket that surrounds the cylinders.