1988 Mercury 2.0 v6, need some pros on this one.

[88Laguana]

I have two of these engines on a center console that Ive owned for the last 12 years. Ive done all the work on them to keep them running well. Stators, CDIs, fuel pumps, impellers, lower unit oil every fall, fuel lines, steering lines, etc to keep this old girl running good. Run premix 100:1 with amsoil and splash of seafoam every tank. When the engines are running good it rips. I have the service manual and use that for the repairs. I have an issue that I am absolutely stumped on. Starting noticing that the starboard engine seemed low on power this year in the spring and was running warmer than normal. It would still run ok at high rpm but I could tell it was low on power getting out of the hole and the pee stream seemed weak. Decided to replace the impellers and thats when things started taking a turn for the worse. After replacing the impeller the cooling issue was solved but I then had steam in the exhaust and it still was low on power. So I pulled the exhaust divider plate and replaced the gaskets which were showing signs of leaking. Sweet, easy fix I thought. Well after that repair and now having full cooling system pressure the engine will not run at all. It will start and idle fine right up until water pressure builds. As soon as water pressure builds the engine stalls. Water is getting into the fuel charge somewhere. I did a compression test and was at 120psi on all 6 holes so its not a head gasket. Pulled the divider again just to inspect and no signs of leaks. Replaced the gaskets again. Surfaces look good, no warping or apparent corrosion. So I am stumped here. Where is water getting into the fuel charge? Maybe base gasket? Im worried due to the age that maybe a block crack or corrosion issue. Wondering if anyone who has taken one of these engine apart or know more can point me in the right direction. Thanks for any and all help!

[88Laguana]

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[tlwjkw]

what kinda signs are you seein' that lead ya ta believe is water in tha fuel other than tha "steam" you see.. exactly where is this steam being discharged?.. any gunky stuff in tha carb throats or prop exhaust?.. piston tops or plugs look "washed"?..leaky head gasket usually does but won't necessarily show up as low comp... water pressure gauge?.. readings at different rpm?.... a gauge will help ta figure it out..

no indication of any bad gaskets so far ya probably lookin' at pullin' it completely apart ta find tha culprit...

i would pull tha heads, have machined ta make sure they are flat and put new gaskets on it for a start...

100 ta one?.. really?.. you are a brave man even if its amsoil....

[LakeFever]

100:1??? Yikes

[rock]

That 100:1 kinda scared me a little.

Rock

[FUJIMO]

...if you really have been always mixing at 100 to 1...i think i know what your issue is. pull both heads next...

[tlwjkw]

says he's been runnin' that way for 12 years.....:leaving:

one of 'tha 2 stroke AMSOIL's recommends it at 100 ta one... think its called sabre or something similar???

[skialot2]

I would pull the heads. Look for a blown gasket or a crack. If water is getting into a cylinder you will be able to tell. I have seen blown head gaskets and cracked heads still have good compression.

[Glastron1987]

I noticed that Amsoil 100:1 oil years ago and always wondered how it worked. Almost tried it but ended up sticking with convention 50:1. I didn't see a cost advantage, but the little bottles seemed pretty convenient. Good luck with the engine. Seems like a bad head gasket would shows a compression issue, but maybe not.

[108]

I've been doing mandatory head gaskets on anything pre 95. They are failing between the fire ring and gasket surface, and 100:1, NOPE.

The little Amsoil trunk slammer came to my shop years ago on his 100:1 soap box when I was doing reeds and injectors on my or a customers 2.5 before we left for Jasper, He got a quick lesson in F and U.

[LakeFever]

Worth mentioning since I’ve been peeling apart motors I’m finding plenty of surfaces that are far from true. Heads with substantial wave etc. old stuff. Needs to be gone over. Check everything and replace all gaskets etc etc etc. it’s the only way to make these old girls run like they should imo. Anything less just starts the game of whack a mole.

That’s how I see it anyways. There’s not too many easy quick solutions to make a 30 year old motor run another 30 years worry free

[108]

The ol 2 liters are about as tough as they get if they survive the oiler gear.

[88Laguana]

Thanks for the replies guys. I completely removed the oil injection and installed the mercury racing block off plates that hold the pump bushing when I acquired the boat. I was recommended the Amsoil by a very well known and respectable mercury mechanic that raced these engines. Here is the product.

https://www.amsoil.com/p/amsoil-100-1-pre-mix-100-synthetic-2-stroke-outboard-oil-ato/

Engines have been running great for 12 years on this mix so I can stand behind it. I was shocked when I first heard 100:1 too but it works. The price is the same as running regular style oil at 50:1 since the amsoil is ~$15 a quart. Just makes it easy to do 25 gallons per quart at fillup.

Anyway getting back to my issues it seems the recommended route is to pull the power head and go through it all. I agree this is probably the correct course of action due to the age of the engine. Even with good compression the heads / head gaskets can still be letting water by? The reason I think water is getting into the fuel mix is the more I fixed the cooling system the worse it ran, until I had the cooling system 100% fixed and full pressure it stopped running as soon as water pressure builds. When the cooling system was low on pressure it ran ok but low on power due to only a little bit of water getting where it should not be. Now that the cooling system is full pressure I suspect where ever it is leaking it is leaking bad. Leaking or blowing by water from somewhere it now stalls as soon as water pressure builds. I suspect water maybe getting into the crankcase as it stalls hard. I feel if it was getting into 1 cylinder it would sputter and run ****ty but not just completely die.

So the advice here is to pull the engine, and start taking it apart, take to machine shop to resurface things after a full block inspection? Gotta work fast.. Michigan here and its about to start going below freezing in the the next few weeks.

[Glastron1987]

Just a side question, but how much smoke do you get from the amsoil 100:1? Seems it would run pretty clean.

[88Laguana]

It runs very clean. At idle its a little smoky like any 2 stroke out of its efficiency zone, but once you give it some air to go with that fuel mix the exhaust is almost like a 4 stroke. At WOT there is no smoke at all.

[88Laguana]

Going to try and pull the heads this weekend for inspection before it gets too cold and I have to shrink wrap it until spring. Will keep the thread updated.

[Glastron1987]

It runs very clean. At idle its a little smoky like any 2 stroke out of its efficiency zone, but once you give it some air to go with that fuel mix the exhaust is almost like a 4 stroke. At WOT there is no smoke at all.

I have several (old) boats so may try some of that Amsoil on one of them.

[88Laguana]

The amsoil works great. Also my Johnson 9.9 kicker has ran on that mix for the last 12 years, mostly at idle and it still runs great and is clean. So I pulled the heads to inspect and they don't appear warped but I could tell from some missing washers that the heads have been pulled before. Probably gasket replacements? Figured I would post the pics and see what you guys think by looking at them since this is the first time Ive worked on one of these engines. Obviously I need new gaskets now but do these look in rough shape? The cylinders look pretty clean, def water getting in there. From these pics does it look like water is getting past the gaskets?
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[skialot2]

Gaskets don't look great but its hard to tell from the pictures. Pistons look like they got a little washing. What do the cylinder walls look like? Check everything very thoroughly for cracks.

[Glastron1987]

I'm not an expert at reading those, but the outside edge of the gasket on the right-most cylinder looks a bit suspicious.

[tlwjkw]

cyl. # 1 is definitely washed.. 2 and 4 maybe.. gasket in last picture is popped on what looks ta be number 1?..

[88Laguana]

Well I had to hose the cylinders down with some oil and close it back because the rain and wind started to pickup. Looking closer at the pics I can see some spots on the gaskets that look like a lot of blowby. Cylinders walls looked good but I did not inspect them very well, really I need to turn the engine over with the heads off and inspect each one. Just have the heads snugged on right now with good covers on the engine. Supposed to be nice and sunny tomorrow, will try and pull them again and get a flashlight in each hole while turning it over. This pic really shows what appears to be blowby: upper left and middle left
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Another reason I wanted to pull the heads is to see what gaskets I needed! Lots of different styles.

[88Laguana]

Well I ordered and have on hand 2 new head gaskets. Also found a shop nearby that can true/ resurface the heads. The bad news is winter is here so the boat just got shrink wrapped until spring. To be continued…

[Glastron1987]

Maybe that will do it. Please update us in the spring.:)

[donmac]

I ran amsoil in bridgeport 2.4 offshores and never varied always 40:1 and never had to teardown an engine for the entire season! I thought you were premixing and running injection, that's how I run my sled,just in case the mapping encounters a lean spot! more gas,less oil makes more power but not enough to warrant that risk,unless your never over 5000rpm and a light load your pushing! 2.4's pushing a 24 skater 7200rpm would see over 210F on a long leg! you need lots of oil to keep that bridge lubed and cool so your not peeling chrome!

[88Laguana]

I ran amsoil…

I premix Amsoil at 100:1, oil injection is removed. Ive ran 3 engines on this mix for 12 years without an issue. 2 merc 2.0s and a johnson 9.9 kicker. Granted, this is a fishing boat and the engines see around 4k max. Ive got fuel flow sensors and after 4k rpm fuel milage falls off a cliff. This current issue I believe is due to age/hours of the main engines. Now if this was a race vessel and I was spinning 7k, for sure I would not run 100:1.

[Jim Speros]

Head gaskets were definitely weeping. One telling part I notice is the dark color over the yellow in the water jacket areas. On your heads is it yellow under the flat black? I recall that area bearing yellow too like the block.

[NZ Sidewinder]

Lol
Those motors deserve a minimum of 40 to 1 fuel oil.
35 to 1 is my number.

[88Laguana]

Lol
Those motors deserve a minimum of 40 to 1 fuel oil.
35 to 1 is my number.

The only oil I would ever run at 100:1 is the Amsoil full synthetic. It is designed to run at that ratio. Its twice the cost of standard good 2 stroke oil, so not saving any money running it like this. They have ran perfect on this mix for 12 years and over 600 hours. Always ran cool and efficient. Also run Amsoil full synthetic lower unit oil changed every season (~50 hours) and impellers changed every 100-150 hours. Always winter stored with seafoam in the fuel system and carbs. These engines are 1988 and live in michigan so I really believe its just age and climate that are at fault here, not the fuel mix. For instance, right now the boat is shrink wrapped and covered in ice! I checked it out the other day on my way ice fishing. Got a few more months of winter until I can get back to working on the engines.

[NZ Sidewinder]

The main reason I'd run oil rich on those motors is because they are bottom guided conrods and probably plastic cages big end bearings.
I like the crank on those motors to run in a slurry of oil to ensure there is enough volume of oil getting to the journal and rod guides.

[Glastron1987]

The only oil I would ever run at 100:1 is the Amsoil full synthetic. It is designed to run at that ratio. Its twice the cost of standard good 2 stroke oil, so not saving any money running it like this. They have ran perfect on this mix for 12 years and over 600 hours. Always ran cool and efficient. Also run Amsoil full synthetic lower unit oil changed every season (~50 hours) and impellers changed every 100-150 hours. Always winter stored with seafoam in the fuel system and carbs. These engines are 1988 and live in michigan so I really believe its just age and climate that are at fault here, not the fuel mix. For instance, right now the boat is shrink wrapped and covered in ice! I checked it out the other day on my way ice fishing. Got a few more months of winter until I can get back to working on the engines.

Yeah, your issue does not sound oil related.