1971 Merc 800 rebuild / refurbish

[Maxz695]

Re: 1971 Merc 800 rebuild / refurbish

Good to here the wear sleeve is in perfect shape Be sure all reeds are flush to the blocks or poor carcburetion. Also you can and must be aware you can only use the power case (INTAKE) off the donor block to use with the donor block. They cannot be interchanced asl well. I f you are unsue of anything please fell free to post. I finninshed my rebuild and will be testing open water tommorrow. No Knock I,m so happy!!! Scincerely Maxz695

 

[Moody Blue]

Re: 1971 Merc 800 rebuild / refurbish

Did a bit of reading about the reed blocks. Not sure now if I should replace mine or not. Measured the labrynth depths as follows.

Reed block halves w/dowel pin measured 0.040" deep. Ridges are square and sharp.

Reed block halves opposite dowel pin measured 0.028" deep. Ridges are slightly mushroomed.

By comparison, the original reed blocks measured 0.034 deep and 0.021 deep.

These are no longer available new, and I can't see buying a used set because they probably are not any better then what I've got. Is there any way to refurbish them? Will cleaning up the mushroomed edges help at all?

Is there an alternative part that can be used as a substitute?

 

[Moody Blue]

Re: 1971 Merc 800 rebuild / refurbish

Good to here the wear sleeve is in perfect shape Be sure all reeds are flush to the blocks or poor carcburetion. Also you can and must be aware you can only use the power case (INTAKE) off the donor block to use with the donor block. They cannot be interchanced asl well. I f you are unsue of anything please fell free to post. I finninshed my rebuild and will be testing open water tommorrow. No Knock I,m so happy!!! Scincerely Maxz695

I'll put together the best combination of parts that I can and hope for the best. I am aware of the matched block and case cover, but thanks for the heads up.

Good luck with the sea trials.

 

[Maxz695]

Re: 1971 Merc 800 rebuild / refurbish

May not be much help but the reed blocks themselves rarely lose formidity, They should be reusable even from the donor motor. I slammed my steel reedblocks with a hammer trying to seat them and indented them. I used the aluminum replacents for am 60 HP crank i,m running now. When I removed it to replace my used three 3 rods I inspected the center mains to find out even though the carnk was pristine the races had major wear. I replced them with another set. I replaced several reeds to the blocks and have great intake and carburation. I will be testing on the water thommorrow. I can.t see how the reed blocks themselves are that bad unless due to overheating? You are going to use the donor block and lower case (INTAKE) Is there any other indication of wear to the block for the reeds other than the measurment like hitting or pounding it? In my opinion and it,s only an opinion use the upper reedblocks from both engines if they look good as opposed to replacing as the lower reed blocks if damaged would take the worst of the overheating first. Then swap the best reeds to those blocks JMO

 

[Faztbullet]

Re: 1971 Merc 800 rebuild / refurbish

Is there any way to refurbish them? Will cleaning up the mushroomed edges help at all?

No and cleaning them up wont help.....sorry :blue:

Is there an alternative part that can be used as a substitute?

Yep... any inline merc reed block from 40 hp to 150hp..:joyous:

Posted by Maxz695....May not be much help but the reed blocks themselves rarely lose formidity

They dont lose their shape but the labyrinth seal grooves do wear out...

Posted by Maxz695...I cant see how the reed blocks themselves are that bad unless due to overheating?

Overheat did not damage and wear these but is usually from overpropping and lugging motor. The crankshaft at 5000rpm is like a spaghetti noodle and actually grows in length and flexes between journals.This is why you prop to the max rpm side of recommended range.
Moody ...pm me your address and I will send you a couple of reed blocks and good center main as I am cleaning out out my inline parts. I might have some pistons left but I throwed about 60 away last week. All I ask is refund on shipping....

 

[Maxz695]

Re: 1971 Merc 800 rebuild / refurbish

OK I see The reed block centers are like my 40 HP and set right on the crankshaft as my 70 have the center mains between the crank and the reed blocks. I have 2 full sets of pedals and reed stops as well as two blocks 40 HP. they all sat flush to the blocks, but like he said the reed blocks are no good (Mushroomed somewhat)

 

[Moody Blue]

Re: 1971 Merc 800 rebuild / refurbish

No and cleaning them up wont help.....sorry :blue:

Yep... any inline merc reed block from 40 hp to 150hp..:joyous:

They dont lose their shape but the labyrinth seal grooves do wear out...

Overheat did not damage and wear these but is usually from overpropping and lugging motor. The crankshaft at 5000rpm is like a spaghetti noodle and actually grows in length and flexes between journals.This is why you prop to the max rpm side of recommended range.
Moody ...pm me your address and I will send you a couple of reed blocks and good center main as I am cleaning out out my inline parts. I might have some pistons left but I throwed about 60 away last week. All I ask is refund on shipping....

Message sent. That is very generous of you, and I very much appreciate the offer.

Are you getting out of the service business, or just purging parts from the OLD Mercs?

 

[daveswaves]

Re: 1971 Merc 800 rebuild / refurbish

Message sent. That is very generous of you, and I very much appreciate the offer.

Are you getting out of the service business, or just purging parts from the OLD Mercs?

Hey MB, I have lots 0f reed petals and blocks here. If you don,t get what you need from FB let me know'

 

[Faztbullet]

Re: 1971 Merc 800 rebuild / refurbish

Are you getting out of the service business, or just purging parts from the OLD Mercs?

The inline work is slowly fading away as nobody want to put $1000 in these old motors as they can be replaced with later model for a couple hundred more. I am just getting rid of extra parts that I dont need...just going to keep a few of this and that to keep my motor going and maybe a few customer repairs.

 

[Moody Blue]

Re: 1971 Merc 800 rebuild / refurbish

Good news so far. I measured up the bores of the donor block and they look great. Measured at three depths in each cyl, both inline with crank and at 90* to crank. Nothing out of round more than 0.002", and the most taper I measured in any cylinder was 0.003". The diameters at the top (plug end) of the cylinders measured the largest at 2.873 and 2.874". Not a mark in the bores.

I have a stone - three legged type cylinder hone with 240 grit stones. Is this an acceptable tool to hone the cyls? Would hate to screw up those bores with the wrong tool.

 

[Maxz695]

Re: 1971 Merc 800 rebuild / refurbish

I would wait for fastbullet to reply That seems to be a medium grit stone which might be ok but I think 320 would be a finnishing grit stone. so please wait for proper assistance in that matter. No honing at all may be nessecary if they look that good. Sounds like you have a good block to work with there moody blues again please wait for professional advise.

 

[Moody Blue]

Re: 1971 Merc 800 rebuild / refurbish

Have ordered new rod bolts but was wondering if the NUTS should be replaced as well.

 

[Maxz695]

Re: 1971 Merc 800 rebuild / refurbish

It might be a good idea I have reused the old ones with no incedent on 2 engines. With the money your putting in better safe than sorry is all I can suggest. They cant be that much more for piece of mind so I would go for it and rest your mind at ease.

 

[Moody Blue]

Re: 1971 Merc 800 rebuild / refurbish

Pulled the upper and lower main bearings off the donor crank today. No easy task. Those bearings are NOT a slide fit for sure. Used a bearing separator to move the bearings away from the crank journals, then used a gear puller to drag them off the rest of the way.

Interesting find on the upper main bearing. Once I got the bearing off the crank, I discovered a thin shim washer (0.010" thick) between the bearing and the crank journal. This is an original Merc assy, so that shim went on at the factory, BUT there is no record of it in any of the on-line parts diagrams I've seen.

When I dismantled the other crank assy, there was no shim washer present. Any thoughts on this shim washer?

 

[Maxz695]

Re: 1971 Merc 800 rebuild / refurbish

That washer was for end play when you put the crank on you need to attach the upper and lower end cap and center the shaft. That washer was for centering purposes. If the crank is not centered it will bind the rods and wear them down as well as run off center and grind the needle bearings. Use a feeler gauge on both sides to center the shaft. You will see the rods move left to right and niether side of the rod should touch the side in contact with the crank.

 

[Faztbullet]

Re: 1971 Merc 800 rebuild / refurbish

When I dismantled the other crank assy, there was no shim washer present. Any thoughts on this shim washer?

That is for correcting machining tolerance of crank as it was cut undersize at factory...it brings upper bearing back into spec height. It has nothing to due with crankshaft endplay as the end caps control this.

I have a stone - three legged type cylinder hone with 240 grit stones. Is this an acceptable tool to hone the cyls?

If its the cheap spring type do not use it... need a Sunnen hone.
Also your "Red Cross" package went out USPS..enclosed is center main and bearings, 2 new style reed blocks and rod...

 

[Maxz695]

Re: 1971 Merc 800 rebuild / refurbish

so the washer I have as well is to make up lost crank material and the only thing nessecary for end play is the outer brass shims on the endcaps?

 

[Moody Blue]

Re: 1971 Merc 800 rebuild / refurbish

If its the cheap spring type do not use it... need a Sunnen hone.

Guess I'll be sending the block out to get it done then. Local shops are quoting $45 per cylinder for honing. $180 seems high to me but I have nothing to compare it to. Is that a reasonable price? I know that we pay almost double what the same parts can be bought for in the USA.

 

[Faztbullet]

Re: 1971 Merc 800 rebuild / refurbish

Go to a auto parts supply and see if they will rent you one.....

so the washer I have as well is to make up lost crank material and the only thing nessecary for end play is the outer brass shims on the endcaps?

That is correct....I usually set my motor around .006-.008 end play

 

[Moody Blue]

Re: 1971 Merc 800 rebuild / refurbish

Good thought on the rental. Will look into that.

Having trouble finding the upper main bearing. Have read that it is a generic #5206. The local bearing houses carry a #3206 and claim it is an equivalent to the 5206. Only difference is the contact angle of the ball bearings.

Ever heard of the 3206 bearings being used in place of the 5206?