1973 Merc 850 Carb Rebuild

[ShowMeGuy]

I've just picked up a 1973 Starcraft that has a 850 Merc (SN# 3740426) on the back of it. Starts and runs but idles rougher than I'd like. I've got a bid out for a paper Merc service manual but in the mean time I'm slowing taking parts off and researching here on iboats.

What I've removed so far, the side cowling sheetmetal, the top cover and the top/rear plate (reinforcement???) I've removed the front control board & the starter. I don't see how to really get the carbs out with removing the distributor. So being I'm without a SM, I wanted to see what all that is going to affect, etc before I do it. I was also trying to remove the coil wires but I'm afraid to pull to hard as they don't want to come out, followed by the actual coil. Do they come out????

Here are the parts I'm going to or have bought:

Qty (2) 1395-51091 (Carb Repair Kit) Local Dealer
Qty (1) 32-55827A1 Fuel line (Fuel pump to top carb) from Old mercs.
Qty (1) 32-55829 Fuel line (Fuel line adapter to Fuel Pump) Boats. nte
Qty (1) 32-59352 ( I can't find anyone to makes the 6 5/8" carb to carb line.) All my fuel lines are in fair/poor shape and want to get it right when I have it all apart.....

Is there anything else I should do while I'm in there on a "new to me" motor? I'll be researching on sync'in the carbs and the timing once I get the carbs out at least. I'll be putting them in chem-dip so they should be squeaky clean when done.

Just a few pics of what I'm tearing down..

Thanks!!!!

 

[wired247]

Re: 1973 Merc 850 Carb Rebuild

The spark plug and coil wires are screwed in. Pull the boot back a bit and unscrew them.

 

[chum1]

Re: 1973 Merc 850 Carb Rebuild

looks like a clean machine and in good hands with the likes of those toolboxes in the background

 

[mr 88]

Re: 1973 Merc 850 Carb Rebuild

To the best of my knowledge you do not have to or want to remove the distributor.I have only dealt with the Towers, there is less room there and have never removed the distrib to get at the top carb. The front plate comes off and hangs off to one side. You should be able to get a open end wrench on the 7/16" nut and break it free.Fingers can walk them after that.You may need a stubby 7/16 '' wrench or one with a slightly different angle to get at the upper starboard nut.Maybe do a search on here for someone that has done it and has pictures.I would also leave the wires plugged in,unless your into opening a whole new can of worms.

 

[1960 Starflite]

Re: 1973 Merc 850 Carb Rebuild

I just rebuilt the carbs on my 1975 850, s/n 429xxxx. Didn't have any problem removing them. I had the front cover off. Used a 1/4" drive socket set with swivel extention. Just be VERY careful removing the carbs. That plastic throttle joint between the carbs is VERY fragle. The older inline Mercs used a steel flex cable to make the connection. Can you say cheap plastic?

Also check the timing belt. Mine broke while removing it to pull the flywheel, (bad stator wires).

Tom on Buckeye Lake

 

[ShowMeGuy]

Re: 1973 Merc 850 Carb Rebuild

I just rebuilt the carbs on my 1975 850, s/n 429xxxx. Didn't have any problem removing them. I had the front cover off. Used a 1/4" drive socket set with swivel extention. Just be VERY careful removing the carbs. That plastic throttle joint between the carbs is VERY fragle. The older inline Mercs used a steel flex cable to make the connection. Can you say cheap plastic?

Also check the timing belt. Mine broke while removing it to pull the flywheel, (bad stator wires).

Tom on Buckeye Lake

Thanks for the heads up on that little plastic piece that ties the two together. I'll have to get my 1/4 drive stuff out.... Might have to make a trip to sears and get a swivel head as you say, I was thinking that would be the only way to get those out.....
The PO just had the timing belt replaced and I have the reciept to show that. I'm going ot have some questions on the re-sync of the carb just well cuz I wanna know how to do it.... and then I have a baseline on the motor as I know it.

 

[ShowMeGuy]

Re: 1973 Merc 850 Carb Rebuild

looks like a clean machine and in good hands with the likes of those toolboxes in the background

Thanks Chum!!! Those babies make me extra dangerous in the shop... lol...

 

[ShowMeGuy]

Re: 1973 Merc 850 Carb Rebuild

The spark plug and coil wires are screwed in. Pull the boot back a bit and unscrew them.

10-4.. I'll be checking that out tonight when I get back home from out of town...

 

[chum1]

Re: 1973 Merc 850 Carb Rebuild

Thanks Chum!!! Those babies make me extra dangerous in the shop... lol...

LOL like they say: "if it ain't broke, I'll break it for shore"

 

[ShowMeGuy]

Re: 1973 Merc 850 Carb Rebuild

Got the carbs off with the 1/4 drive swivel and extensions.... I had to remove the coil as well... But I didn't see where the wires are screwed in anywhere?????? So all are still connected.... Try to get a pic....
I see what Starflite was saying about that cheap azz plastic piece that connects the two carb main butterfly's together... pretty chinsy...
Won the ebay auction for the SM.. Should be here end of week I hope for any future deep endeavors...
I am going to try to snap pics of the removal of the parts and replacement of the lines etc..

 

[ShowMeGuy]

Re: 1973 Merc 850 Carb Rebuild

Got the top Carb taken out and apart last night. Looked very good I thought, except the float was cracked and looking to be in rough shape so I'll just pick up 2 of them today at the boat dealer PN#1395-8673. I dumped it in Chem-Dip overnight even though I thought it didn't need it. Took it out and blew air thru it this AM.
The bottom ones is looking to be a different story, as the screen cannister was full of crap... So I'm interested in how the inside will look when I crack it open tonight. I wanna put the other one back together first incase I need to use the bottom one for reference!

Now I'm still looking for this part!! Who knows where I can get one???
*****************************************************************
Qty (1) 32-59352 ( I can't find anyone to makes the 6 5/8" carb to carb line.) All my fuel lines are in fair/poor shape and want to get it right when I have it all apart.....
*****************************************************************
Thanks in advance guys!

 

[1960 Starflite]

Re: 1973 Merc 850 Carb Rebuild

Just went back and looked at your pics. ME WRONG, yours has compression fittings mine has barbed fittings.
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You go GUY, About the fuel lines. Just go to Autozone, NAPA, Ect and buy four feet of 1/4" fuel hose and several hose clamps. Nothing special about them. Use side cuts pliers to cut the OEM clamps and a knife to split the old hose, then replace with your new hose. You'll have to pull the starter sol. to get to the hose connected to the quick connect.

 

[ShowMeGuy]

Re: 1973 Merc 850 Carb Rebuild

The big bottom plug was in there pretty good.. had to take the drill and punch to it and got it to back it out that way. Then I lost one of hex plugs that covers up the jet witht he little washer/gasket or well one of my little "helpers" kicked it or well who knows.. lol.... Got one bought last night...

I got a plan on how to make a new carb to carb hose with some 45' fittings and some barb fittings.... More to come on that after the trip at lunch.

Couldn't find the camera this AM.. :*(

 

[Kmyers]

Re: 1973 Merc 850 Carb Rebuild

I see that it was a while back when working on this motor but I am about to try the same thing on my new to me 1973 850. All of my parts will hopefully be here later this week. I am doing carbs, fuel pump water pump kit except upper and I did go ahead and buy two new floats just in case. I will not have a manual but I hope with all the talent and knowledge on this site I will be able to get some help if needed. Did you have success after you got all put back together and did you run into any other problems I should look out for? I did notice the plastic throttle linkage was you able to take it off before removing carbs or did you have to do it after? I appreciate any help you can give.

 

[ShowMeGuy]

Re: 1973 Merc 850 Carb Rebuild

I see that it was a while back when working on this motor but I am about to try the same thing on my new to me 1973 850. All of my parts will hopefully be here later this week. I am doing carbs, fuel pump water pump kit except upper and I did go ahead and buy two new floats just in case. I will not have a manual but I hope with all the talent and knowledge on this site I will be able to get some help if needed. Did you have success after you got all put back together and did you run into any other problems I should look out for? I did notice the plastic throttle linkage was you able to take it off before removing carbs or did you have to do it after? I appreciate any help you can give.

The only thing that I ran into afterwards we a faultly or cracked bowl straight out of the package. Didn't catch it when I put it in. That had be puzzled for a little while and initially setting the idle speed to low. It would bog when shifted into gear but that is all squared away. Setting the floats is pretty easy as well. There are posts in here with pics if you don't have the manual.
The plastic parts and pieces are pretty fragile... be careful as you can't buy them anymore new. I took both carbs out together and then removed the plastic parts. Install was reverse....

 

[turtles11756]

Re: 1973 Merc 850 Carb Rebuild

Got the top Carb taken out and apart last night. Looked very good I thought, except the float was cracked and looking to be in rough shape so I'll just pick up 2 of them today at the boat dealer PN#1395-8673. I dumped it in Chem-Dip overnight even though I thought it didn't need it. Took it out and blew air thru it this AM.
The bottom ones is looking to be a different story, as the screen cannister was full of crap... So I'm interested in how the inside will look when I crack it open tonight. I wanna put the other one back together first incase I need to use the bottom one for reference!

Now I'm still looking for this part!! Who knows where I can get one???
*****************************************************************
Qty (1) 32-59352 ( I can't find anyone to makes the 6 5/8" carb to carb line.) All my fuel lines are in fair/poor shape and want to get it right when I have it all apart.....
*****************************************************************
Thanks in advance guys!

the fuel hose may be available at oldmercs.com

 

[Kmyers]

Re: 1973 Merc 850 Carb Rebuild

My hose from carb to carb is bad also, my plan is to get male pipe thread to male nipple fittings and change all over to regular hose clamps

 

[mercurymang]

Re: 1973 Merc 850 Carb Rebuild

Just curious. Why by fuel hose from mercury. Any fuel hose will be fine.

 

[ShowMeGuy]

Re: 1973 Merc 850 Carb Rebuild

My hose from carb to carb is bad also, my plan is to get male pipe thread to male nipple fittings and change all over to regular hose clamps

That is what I ended up doing for the hose on the the carb to carb connection. Just have to be careful on where you put those hose clamps as they can only go in a few places without being in the way of the starter and other parts. Git r Dun.