TOPIC: 850 FGS

Recently purchased this beauty and found time to take a look with the following results;
1) 105, 2) 115, 3) 105, 4) 110, 5) 120, 6) 90.

This will hopefully be powering a 19' Sabrecraft Commander.

Another pic

one more

Hoos
Another short white stack being put back into service. Excellent!
Keep us posted.
Neil

Neil,
I will post updates on the forum when I can. I did open up the upper and mid transfer ports to inspect the cylinders yesterday. The rings were free, had spring and I did not see any scoring. From what I have found out the boat which the motor came with was last registered in 2005. I would like to try and start the motor, but with a small workshop, 18 degree whether, and 10" of snow falling I will have to wait till things warm up.

CDH

CDH,
Sometimes I feel like the Grim Reeper with my posts, but I hate the thought of an otherwise salavageable old Stack-6 dying a slow noisy death rather than being rescued to run another 30-40 years.

If the beast has been 'parked' since '05 and if the #6 compression reading is accurate, you might have discovered why the beast was parked.
Low compression in #6 suggests that perhaps the bottom end cap's crankshaft seals might have failed consequently causing #6 some grief so try and get a peek at the #6 rings and cylinder wall.

Another caution to consider after a long lay-up is whether or not ambient moisture has settled in and compromised the bottom end-cap's crankshaft main bearing so it might be wise to consider lifting the powerhead and removing the end caps so you can inspect and replace the upper & lower main bearings and related endcaps seals.

THEN,...Since you're 'in the neighborhood anyway' you might as well pull the rotating assembly and make sure all the rings are free and the skirts and cylinder walls are A-Okay.

Having said all that - once you hear the old girl fire up you'll be proud of your accomplishment.
Thom

Thom,
Thank you for your advise. I was concerned about the #6 reading as well and ran the compression check twice over the block to make sure. I am what you might call a novice mechanic, able to turn a wrench enough to get me in trouble, and do not want this motor to "die a slow noisy death". Is this something I should do myself or find a Dr.?

CDH

CDH,
Most of it is pretty straight forward basic stuff, but a few specialized tools are required and an experienced eye to spot problems can be very helpful if not essential.
There will be a special feeling of accomplishment experienced when you accomplish the task personally and believe me when I say that the fellows that post here will be those eyes of experience over your shoulder when you post questions and pictures related to the seemingly simple up to the 'haven't got a clue' levels.
You can probably snag any tool you don't currently own at Harbor Frieght or a similar outlet, except the ring compressors required to re-assemble.
Depending on where you live or your progress the ring compressors might be easy to access through one of us.
Also, depending on your location, you might just be close to on of the Stack Masters that can guide you or take on your project if you opt to have everything done for you.
Thom
ps: I see you have the 90ci TIGER 850 rather than the 76ci 850.
Very cool.
If you discover you need more horse power your 850 can be boosted to 100 horse power using a few parts from an early 1000.

Thom,
Thank you again for the advise. I think I will be reading the service manual in detail over the next week and consider the next step. I was excited when I ran the SN and found out it was a 90ci. This beast is a thing of beauty in MHO.
CDH.

I agree 1000%,...The Cloud White and stainless Stacks are beautiful.

In regards to the serial number - it sounds like you might just have something original with numbers matching the serial plate you found and the TIGER nestled into the cowlings.
There should be a matching serial number stamped into the top of the engine block just aft of the flywheel in very small stamped numbers.
Just in case you haven't spotted it yet I circled the TIGER cast into the block.
Since the swivel housing that has the serial number plate on it can be swapped around through the years it is always nice to have another way to tell at a glance what you're looking at when you go parts hunting.
At a glance and without serial numbers, etc seeing this TIGER logo tells you real quick that you either have a 90ci or 93ci Stack-6.
'Nuff fer now.
Thom

The flexplate flywheel means 90 cu in not 76. The larger stack 93 cu in like the 1100 won't bolt on to your mid so unless someone did a lot of reboring etc. to transfer in larger pistons you have a 90 cu in block which is great because pistons and rings are easily found. Are you calling the top cyl #1 or #6 ? It is not unusual to see the top cyl comp low due to water pump issues, and poor cooling this is typically considered #1 cyl. If #6 is your bottom cyl then low comp may be due to poor access to install your compression gauge fitting. This bottom cyl is almost always OK as it is the last to lose cooling, it is however per Thoms comments the most prone to rust, it being closest to water flow etc. That would for sure effect your compression as the rings would be stuck.
In any event it would be a huge mistake not to refurb the PH before you use it, every seal and gasket is nearly 50 years old. Distributor bearings are usually catchy and need replacing. They are standard sizes so not to expensive form a supplier not your marina. Good idea to disassemble starter and relube the armature shaft to.
I have been digging around reconfiguring my workroom and have a VERY nice face plate for the 850 I also have a complete 850 PH been indoors for a long time on my bench, it's super clean. I kept it as a back up in case my 1000 grenades biut I have several 1000 blocks that are good so I can thin the herd.
Eventually this is all going on ebay so if it would help now is the time.
Randy

P.S. I'm surprised your commander takes a short shaft motor, better check that. If planning on cutting the transom down beware it will cut the freeboard down a lot in the back, not a very desireable situation. Lots of 20 inch mids are available and the shorties are not as common so you could probably work out a trade with some one.
Just thinking outloud...
Randy

Thom,
I did spot the TIGER on the block but did not know what it was referring to. I will check the top of the block for the corresponding SN.

Randy,
Thanks for your input, as a novice it is much appriciated. The #6 is the bottom cylinder. I did wonder if the low reading was caused by difficulty installing the guage, but thought I had a pretty good seal between the fitting and the block.
This motor was with the commander when I purchased it and I am pretty sure it was used by previous owners. I have no plans on cutting down the transom but will look into your suggestions.
CDH

SN from top of the block.

I have seen a number of used late model power TT units on ebay. I was wondering if anyone could tell me what year(s) PTT would retrofit this motor. I have been reviewing recent post which suggested looking for a "craigslist" motor to salvage but did not what year(s) to look for.
CDH

The power trim that will fit easily to this motor is the type that has a ram on the outside of each transom clamp and replaces the shock absorbers.
It will have (2) hoses from each ram (commonly referred to as a (4) hose system) and the trim pump will be the type mounted inside the boat.
I'm not sure exactly that Merc started putting these on, but they were the first style introduced sometime in the late '60s and were used until about '80-'81??
In that era the power trim system found on any 650-4, 800-4, 850-4, 900-6, 950-6, 1000-6, 1100-6, 1150-6, 1250-6, 1350-6, 1400-6, or 1500-6 will fit whether it is on a long or a short shaft motor.
I am not positive, but I believe the same system would work on the 500-4, 650-3, 70-3 of the '70s era.
The style PT seen on my 800FGS in the attached picture is what you're looking for. These actually came off a '78 1150.
Once they are painted Cloud White they look like they were original equipment.
Thom
PS: Some of us are working on making the late '80s integral (3) ram system fit the oldies, but that scheme is only possible for a long shaft oldie.

I have a set of pistons and brackets with hoses.if any one needs.

I have lots of Mec lit from the 60's. It looks like the PT&T became available in 67 for the inline 6's. With a retro kit for earlier in line 's (FGS versions only) This set up would fit the bigger 4's but Merc only refers to the 6's at this point in time.
One thing to be aware of is Merc recomended changing the swivel bracket on the earlier motors if converting. A comparison of parts shows the swivel pin is larger on later models which is what takes the load between the motor and the swivel braket. Also note that the swivel bracket is beefier around the tilt tube on the later motors, again this takes all the load between the swivel and the clamp brackets. Clamp brackets appear to be intercahngable although the later ones have a bolt ear up high on them the earlier ones don't. As a side note, I have never seen an installation using these upper bolt holes even though Merc says through bolt there, I don't use them on any of the installs I have either. I just use the bottom ones.
Swapping to the heavier swivel assembly for a long shaft would prove to be easy as these are easier to find, probably the donor motor for the tilt set up would also have the needed swivel/clamp assembly. Understand visually they are nearly identical but different in critical areas none the less.
The short shaft versions are more problematic because of parts not as readily available.
This all said, recognizing that the early motors have a lot less HP than the later motors and that our application on an old boat would not really see severe service, like would be seen in a surfacing prop installation the smaller earlier stuff is probably just fine.
I would not worry about it, where you have a shorty, there is less leverage on those parts to boot.
I just posted this info more as Merc trivia. Thom is dead on about what to look for. If it turns out the donor has he correct bigger swivel stuff you might as well swap it over.
Randy

The weather has warmed, the workload has subsided and I finally got a chance to get out to the shop. I decided to take your advice and lift the block to get a better idea. With a bit of help from my brother lifting the block, here is where I got to today.

A couple more

over where the fuel pumps are mounted take off the intake port covers and check the cylinders on that side as well. Look for scoring. I have nos rings, pistons, rods and bearings for these. These are some of my favorite mercs. The 800 850 and 1000 they are the coolest looking and sounding motors.

G3,

This is my first Merc and I agree this motor is a thing of beauty. I took the transfer port covers off during my initial inspection and checked the rings on the top and mid cylinder but could not get access to the lower cylinder due to the lower cowell. I checked all three ports again after pulling the block. The rings on all three were free and had spring. The pistons seem fairly clean with little or no sign of scoring. I have not split the block yet to get a good look at the cylinders but will post pics when I do.

CD

she may just need a good cleaning. Even though rings are springy on the side sometimes on the top and bottoms where you can't see they goop up. keep at it!
JIm

Yes,...Continue. There is a lot of carbon deposits and I see a small scoring through the exhaust port on one piston - so keep digging. It will be worth it.
It is a perfect time to start the hunt for a 100 hp baffle plate to replace the 85 hp stainless baffle plate with and a great time to hunt down a set of 100 hp carburetors if you're interested in converting to a true 100 hp - or Merc 1000. Those are to only mods required to have a real 'sleeper'.
Thom

i have a set of merc 1000 carbs if needed.

Thanks for the encouragement. I will be back at it today and try and post some more pictures later.

CD

Today's progress.

Dr,

I believe this is the piston you are referring to.


I am worried about the rust I am seeing. My guess it is from ambient moisture getting into the block after being stored outside for so long.

The surface rust is not much of a concern, it can be cleaned up. The big concern is the condition of the rod and crank journals, rust there is a problem. Split the rod caps and take a look, but keep the bearings matched with the journals for assembly. Also, mike the bores for straightness, more than .005 out of round and it is time for a rebore and new pistons, IF you can find them. Sometimes it is better just to find another block in that case. Great engine however and well worth the trouble of rebuilding it.

Take zip lock bags and sharpie what piston/rod everyting came from and dissasemble. Look at the reed blocks for broken reeds, cracks in the blocks and worn lab seals.

I mark the top of each rod to I know how it went on the crankshaft. The caps usually have alignment marks but if they dont just mark them.

I bet this thing will be great, just need to tear each rod end down and the main bearings to see if there is any rust on the bearing surface. Remember bag and tag everything and take your time and lots of pictures if needed.


The lab seal is the machined grooves in each reed block that go directly over the crank. They keep the crank pressure from being pushed back in forth between cyls and messing up impulses.

The lab seals sould not show much wear on them. post picks once you have them split.

Conrad

Made a bit more progress last night. Removed the rods from the crankshaft.

I did not see any rust on any of the rod bearings or crank at the bearing surface. I have not inspected the main bearings yet. This is a typical image of the bearings I am seeing. They look clean and in good shape.

I am seeing some black deposits on the pistons themselves but the surface seems to be smooth.

Sorry, here is a typical picture of the bearings.

I am having a hard time posting more than one picture at once.

Thanks again for all your advise.

CH

Thanks Jim,

here are the upper and lower endcaps as well.





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when you want to ad a picture click on edit post and where the file attach for img is just stack another photo it will not delete the fist photo you selected there.

The lower main bearing shows the importance of taking the time to pull the end-caps and replace the bottom main bearing and related seals & O-ring. The moisture in the ambient air oozes its way down via gravity and can ruin an otherwise good main bearing.

I'm not sure if I'm seeing reflections or actual scoring in the two areas I have circled in picture number 'Guts_021'.
If either area, or others similar in appearance in other pictures, can be fealt with a finger nail you'll need to see if someone with a true cylinder hone (not a deglazing hone commonly used in a drill motor) can clean those areas up and still stay within factory specs for the cylinder diameter.
Thom

It has been a bit of work to get to this point. My 16 x 10 shop doubles for and everything shed and it seems like every other sentence in the merc manual refers to a differnt tool which I have to look up and figure out how to improvise and make do.

The lower endcap dripped a a couple drops of water when I pulled it off so I was not supprised to see some rust.

The light in my shop is not the greates and I was not happy with the picrures of the cylinders. The next plan before I inspect the main bearings and reed blocks is to clean up the block to take a closer look at the cylinders. As always I will take pictures along the way (hopefully better than the last).

Thank you for the advise on measuring the bore. As I said at the start of this post, I know enough to get me in trouble. I have been looking at calipers and micrometers all day. Is this something i should do myself, do you have any suggestions, or should I just go to the machine shop.

I believe "Guts_021" is No. 3.

CD

Not much progress latley as work has taken priority, but I did get a chance to measure the bores. The bores were measured top, mid, & bottom at three locations and adveraged with the following results:

#1: 2.872
#2: 2.873
#3: 2.872
#4: 2.872
#5: 2.872
#6: 2.873

CD

Noticed some wear while cleaning the block tonight. I do not like what I see and wonder if this may be the reason for the low compression on #6. Any thoughts would be welcome.

CD

The picture is too dark to really see what you're seeing, but if it is the light colored area I have circled in the attached picture - it could be just aluminum transfer off the piston skirt.
Remove it with myratic acid. (I'll write up a detailed explanation if requested as the fumes are dangerous and the acid will attack the surrounding aluminum block if it drips or runs off the steel sleeve and contacts the aluminum)
Once the aluminum tranfer has been removed you be able to make a better determination of whether or not the steel cylinder sleeve is actually damaged enough to cause a problem or not.
Basically - if you can feel any scoring running the same direction as the piston moves with your fingernail - you should post and explain what you have so we can voice an opinion or two on whether or not you should rebuild.

Following is out of the box ponderings that may result in the removal of my Karma - GULP

I would be interested in hearing from anyone that has actually bored out a 90ci block enough to install a 93ci piston.
I'm of the belief that it can't be done and an over-sized 90ci piston for the TIGER block is a rare find.

I would also like to hear from anyone that has successfully taken a 93ci piston (from an 1100 or 1100ss TIGER block assembly - or some 650 pistons) and turned it down to whatever diameter a .015 or .030 90ci TIGER piston would be. (2.890" or 2.905")

Point being on such modifications is that if it is plausible,...The .015 & .030 rings are available for the pistons with 1/16" thick rings as they are the same rings as those used in over-sized 99ci Mercs like an 1150 - 1500, etc.

I'm thinking outloud and out of the box on this one so be gentle if my notions win this week's toaster oven for stupid ideas.
Thom

Thom,

Attached is a markup of the photo showing the area of concern. If you click on the picture it should enlarge it enough to see what I am talking about. Instead of a nice crisp machine edge it appears the block has been hit by something. I do not find any corresponding damage on the piston, but there is some corrosion on the crankshaft which I will post a pic of later this afternoon.

CD