'77 85 HP Johnson

[LiLGrady17]

I was having trouble keeping the engine running once started, but wasnt sure if it was a carb or some other problem. To isolate it, I swapped on a set of carbs from a '76 evinrude 85 from a parts motor to see if the condition changed at all. The engine now ran, but #1 cyl was running rich & missing, sometimes coughing out when I brought the idle down.. I re-did the compression test the correct way, and got pressures of
#2-110 #1-90
#4-110 #3-95
Now, heres the kicker. I was going through the Seloc to see if there are any idle mixture adjustments to be made, and it says there is an idle speed needle valve to adjust but I cant find it on the carb. So I took out the plug over the Low Speed orifice, started the engine thinking I could adjust the orifice and the engine's idle was better. Being amazed by this, I started trying different things. I found out if I keep the LS orifice uncovered, drape a clean rag over the carb inlets, #1 cylinder picks up, Idle smooths out and idles nicely at 7-800 in neutral. Is there an idle speed adjustment to be made on these carbs, and what should I be looking for when I rebuild the carbs to correct this? Thanks

 

[iwombat]

Re: '77 85 HP Johnson

No idle speed adjustment, but you found out that the idle jets are in need of some cleaning. Get a couple of kits and a service manual and rebuild your carbs. It'll be running right in no time.

I am a little concerned about that right bank though. They match each other, so that's good, but why is that side so much lower?

 

[ezeke]

Re: '77 85 HP Johnson

It's probably carbon. Bet there's no thermostat or if there is it is stuck open.

 

[iwombat]

Re: '77 85 HP Johnson

That motor has a single vernatherm for both sides, so I'm guessing that's not it. But I'm liking the carbon explanation.

Have you done a decarb recently?

 

[LiLGrady17]

Re: '77 85 HP Johnson

This is a new-to-me boat & engine set-up.

I haven't done the Seafoam de-carb procedure yet, because it wouldn't stay running at an idle. Plus, the procedure suggests I run it hard afterward to do it right, so I figured once I get it on the water, I'd do it. I'm getting the carb kits tommorrow. The Seloc for J/E 73-91 O/Bs has a carb overhaul procedure, but not anything too detailed. Using the procedure on here & the Seloc, I'm going to give it a shot..

I originally thought, from reading other posts, a stuck open thermostat was keeping the engine cold & misfiring. However the thermostat kits I find online show a different gasket shape than what I have, so I didn't order one. Also, Is the Varitherm in the square water neck piece, or the lower rectangle block type piece below, that the neck mounts on? The reason is, the water neck bolts look good & wound be a simple R&R; The 4 bolt heads holding the lower piece are unrecognizable and will be a more work to remove. I plan to grind off the remainders of the bolt heads, remove the block, then use vise grips on the shafts to remove the remainder of the bolts, but only want to do this if necessary at this point.

 

[jtexas]

Re: '77 85 HP Johnson

seloc has a way of confusing the carbs like that...it's not bad, but your OEM service manual is available - highly recommended. But I"m betting you can get through the carb rebuild. I love my fixed jet carbs - but somewhere in your experiment results is a clue.

There's a "special tool" for removing the orfices, don't try a regular screwdriver, any disfigurement will change the mixture. Instead, cut a screwdriver off flat, and sand it down to form a flat tab like so:

I used a dremel with a sanding band, or a belt sander works.

I'd be real curious to find out how much compression you restore when you decarb.

 

[iwombat]

Re: '77 85 HP Johnson

The vernatherm is in the unit the water hoses connect to. A failed vernatherm is pretty rare though, and I wouldn't suspect that w/o some serious data pointing directly at it.

The carbs are pretty easy. Be sure to remove the jets with a tool described as above and remove the core plug to clean out the idle jets. I'd wholeheartedly suggest getting the OEM manual. FWIW I have the same motor on my '78 starcraft.

 

[tashasdaddy]

Re: '77 85 HP Johnson

like this.

i use this method. Decarb, take a can of seafoam put 3/4 of it in the gas tank, with only 1 gallon of premixed gas. put the rest in a spray bottle. start the engine, and let it come up to temperature. then remove plugs, and them some real good shot of seafoam into the cylinders, replace plugs, let sit 15 minutes. restart, and spray the rest of the seafoam into the carbs, so the the motor almost stalls, wait and repeat until the seafoam is gone.then take for a wide open spin. then put in new plugs, ad premixed gas to the tank, and take it for a wide open throttle spin. it is going to smoke like a house on fire, during this process.

 

[LiLGrady17]

Re: '77 85 HP Johnson

I ground a screwdriver to have parallel edges, and it fit nice & tight into the HS orifice jet. However on the LS orifice, it wouldn't seat in. I had to do a little touch-up grind to get it to seat in. Now, I'm thinking I was correct the first time, & the LS jet is burred from someone else's' screwdriver... I'll grind a new one for the rebuild with TashasDaddy's measurements. Thanks for taking the time to create the diagram.

The prior owner said they could only get about 42-4400 rpm out of it on the water, so it probably hasn't been really run near redline for a while, so carbon may be an issue. Judging by the carb situation, and the overall condition of things, seems he was more of a fuel & go type of guy. Once I get it in the water, I'll do the seafoaming procedure.

The parts '76 85hp Evinrude that also came with the boat now has me thinking. Prior owner said it ran, but not well. It was on the boat when the boat was given to him, and he pulled it to put the Johnson on, because it was running good at the time. The visual condition between the two engines is night & day. It looks like someone maintained the Evinrude. The water inlet screens look nice, the plugs are new, I think a replacement powerpak is there, the bolts have little to no signs of corrosion. I'm wondering if the carb issue was why he pulled it in the first place.

A big collective 'Thank You' to everyone, I'll let you know how I make out..

 

[LiLGrady17]

Re: '77 85 HP Johnson

The local guy only had 1 OMC kit in stock, so I went with the Seirra kits for the carbs. Really a simple job in all. Couldn't find any numbers for the float height, so I just set them level to the housing. I rebuilt the carbs that came on the motor originally, when it wouldn't run. Found small pieces of old silicone squish fragments in 2 low speed orifices, and a bunch of mustardy residue stuff plugging the 3rd. No surprise tho, being the old fuel pump screen filter was really ratty & boat didn't have any other fuel filter assembly on it when I bought it. If anybody does any gunsmithing, the tools work good on carbs too. A small caliber brass rifle barrel brush cleans up the mustardy residue out of the orifice bore threads nicely. Brownells' gunsmith screwdriver set worked out great. The interchangeable tips vary in tip width & tip thickness, so you don't chew up any screws. More importantly, you can get a good torque on damaged screws. One tip fits the orifices perfectly, but it needs to be turned on a lathe to get the shaft diameter smaller, a future project. Can I rebuild my other 2 carbs & shelve them, or should I rebuild them when I need them so the gaskets are fresh?

Anyway, after installing everything, I had the engine idling with the hose flush on, in neutral, steadily at 7-800. When I dropped the boat into the water, the idle dropped lower, 5-600ish. When I shifted into gear, it dropped further & stalled. Tried this 3 times, then I increased the idle screw up, to where it was 6-700 in gear, and it worked great. Rev'ed smooth & strong, right to 5000 rpm. WooHoo!

When I went to flush it at home with the hose on it,now it idles at 1100. I thought it may be cable slop, or the shift box/high idle arm was hanging up, but the idle adjustment screw is against the stop. I'm a boating newbie, so is this normal? and if not, will it do any harm to run it this way?

 

[Reggie08]

Re: '77 85 HP Johnson

I've read 1000-1100rpms on muffs is normal because there's no back pressure on the prop like there would be in the water.

 

[iwombat]

Re: '77 85 HP Johnson

Yep, that's totally normal.