77 Johnson 115 won't hole shot without choke

Greg Boswell

Seaman Apprentice
Joined
Oct 19, 2012
Messages
46
Hi guys,
My 115 was taken to the dealer to have carbs cleaned and rebuilt as they were leaking out fuel causing a nice sheen on the water. They also replaced my fuel lines on the engine and replaced the throttle cables for me and did a tune up and said come get it, it was running great!
So, that was done, but now the motor does not seem to want to reach full power unless I push the key/choke and even at lower speeds it will smooth out RPM and sound when giving it the choke. At full power, I gain a couple hundred RPM and have to choke it to get the hole shot up on a plane. At idle speed, I must blip the choke every few moments to keep engine running smoothly and sometimes at all, and if just sitting there warming up it does make a weird sneeze sound or backfire from time to time after its been at idle for a while. The dealer mechanic said bring it back, but they said it is running fine. Maybe for them I guess if it starts and revs, that means it runs great. In the water, its a bit of a dog without that choke button.
I took the carbs off myself and I thought they looked clean, but used a can of cleaner and sprayed through every little hole and drilling I could see. Made no difference. I rebuilt the fuel pump since that seemed the likely problem, no help. I replaced the little O-rings and plastic parts on the fuel choke solenoid thinking it was somehow sucking air there, but that didn't work either.
My fuel is mixed at 50-1 and is clean. I have all new fuel lines, primer bulb, fuel filter, new fuel pump diaphragm and seals, a clean screen.... I mean it is strange that it will start up and rev up like mad, but under load, does not really want to give me 100% of what it has. It was running all out before I took it in for a carb rebuild to stop the leaking. I know I am missing something, any help would be greatly appreciated. Thank in advance for taking time to read all this, Greg
 
Last edited:

fireman57

Captain
Joined
Aug 24, 2004
Messages
3,811
Re: 77 Johnson 115 won't hole shot without choke

I know that you rebuilt the fuel pump but try this. If you can get it out take a friend and when it does this have him squeeze the primer bulb like a madman and if it picks up and goes your fuel pump isn't working correctly. You may have an air leak somewhere too.
 

Greg Boswell

Seaman Apprentice
Joined
Oct 19, 2012
Messages
46
Re: 77 Johnson 115 won't hole shot without choke

I know, it really seems like there is a fuel delivery issue or vacuum leak that I can't track down. That is a good idea and we'll try that next time out. The fuel pump on this motor is really a very simple basic vacuum operated off of the engine pulse. It would seem that it is just proving partial fuel supply. Thanks for the reply, I'll report back after trying that.
 

fireman57

Captain
Joined
Aug 24, 2004
Messages
3,811
Re: 77 Johnson 115 won't hole shot without choke

If nothing else take it back to the shop and tell them they missed something and that it was running better when you brought it in than after they worked on it. Insist that they redo the work for nothing.
 

emdsapmgr

Supreme Mariner
Joined
Dec 9, 2005
Messages
11,551
Re: 77 Johnson 115 won't hole shot without choke

Having to choke the engine to keep it running is an indication the engine is running lean. That indicates some type of fuel restriction. Fireman's suggestion is a good test. When you said the carbs looked clean, I assume you pulled them apart and visually inspected them. What you can't see in that type inspection is the condition of the fuel jets. The could have debris in them. I'd pull them out and visually inspect them next to a strong light bulb. Also, check the factory specs to make sure the jets are the correct size to the factory parts list: see: epc.brp.com to verify the sizes. It's impossible to see any dried fuel gelatin inside the upper carb body passages. You need to compare the flow rate of the same passages between both carbs during an overhaul.
 

Greg Boswell

Seaman Apprentice
Joined
Oct 19, 2012
Messages
46
Re: 77 Johnson 115 won't hole shot without choke

Yes. I can see how something inside the carbs could be missed. I did take them completely off the motor and went through them as best as I could. I usually run the fuel out of them before putting it up for any length of time over the winter, but here in Florida even so, it is maybe only a few months before its back in service. It's an old motor, 1977 and I bought it as a rebuilt, but it seemed to pull like a horse, just always had a leaky nature that I made the mistake of wanting fixed.
As for taking it back to the dealer and insisting they do it for free. Well, they just say it runs fine for them. It runs, that's the kicker, just not under load without giving it the choke. I did bring it in for another repair to the tilt and trim, but even that was half hitched and I had to redo it to keep fluid from spraying out of the cylinder. Had to let them replace the pivot tube a month or so ago and didn't realize they had left all their tools in the boat until I got it back home LOL. I took the tools back the next day. I get the feeling that I should probably cut my down time and ask for help since I seem to end up re doing a lot of the work I pay them to do or at least seems that way. I have not had any trouble yet with the steering since they put in a new tube. So, that is a nice change.

I don't remember now if I actually pulled the jets out, but I know I did blast the carb cleaner through them very thoroughly. Wait, the main jets are inside the bowl. I did pull the bolt out of the bowls and used a flat blade drive to remove those and they were blasted with carb cleaner. Never thought to check the jet size though. I really can't imagine why the guy would change my jets out to smaller jets. Something to seriously consider.

I believe you guys have helped me confirm my suspicion that the fuel flow is not up to par. I just can't figure out why. I have rebuilt the fuel pump twice, but maybe I should replace it. No kidding, the first time I pulled it apart that diaphragm was like a solid piece of hard paper, but it worked. I might have missed something the first time, but it is such a simple pump, can't see how I missed anything the second time around. Or, could be when they or I replaced fuel lines, maybe one got pinched or the vacuum line to fuel pump is pinched or leaking. It couldn't be simply a matter of adjusting the needles valves on the carbs themselves could it? I can't remember off hand what they are set at, is there a starting point or just what do those things do exactly? Are they just for idle or all around. Been a little leery of messing with them up till now. I'm ready to tweek them and see what happens. I did take them out to clean, but counted the turns and put them right back.
As you can tell from the late reply, just got a pile or work pushed my way today, so this weekend is out for getting back in the boat. But I will let you know how it goes and what I can figure out next time out with it.
Thanks again and if you think of anything else, anything, please pass it on..
Thanks,
Greg
 

emdsapmgr

Supreme Mariner
Joined
Dec 9, 2005
Messages
11,551
Re: 77 Johnson 115 won't hole shot without choke

Checking through the Bombardier Parts and Accessories book, and I don't see that the factory makes a fuel pump rebuild kit for that engine. Their kits start with the 78 model year. There must be some reason why they only recommend a new pump.... (There are of lot of these old pumps that they don't make kits for.) It is unlikely that someone changed the fuel jets, but when you have them out, it's always good to verify that all are the correct size. (sometimes one will get damaged during removal, requiring it's replacement.....) Those carbs are pretty simple, there really is not much to adjust-no needle valves. (just the float valve.) That carb has both main and idle jets...the idles are in the side of the upper body. the factory makes a special small screwdriver to remove the jets. 317002 When you have the carb apart, spray some aerosol carb cleaner thru one orfice on on carb. Note the spray outflow. Do the same orfice on the other carb, noting the spray outflow. They should be the same. Then go on to the next orfice. All should flow the same between carbs.
 

fireman57

Captain
Joined
Aug 24, 2004
Messages
3,811
Re: 77 Johnson 115 won't hole shot without choke

Your high speed jet is behind the drain plug. Run a piece of bread twist tie wire through it and hose it out well with carb cleaner. like emds says. make sure the flow is the same in each carb when you clean them. The needle valve is not adjustable just make sure the float doesn't stick when you turn the carbs upside down a few times. Also make sure the indentation in the float is on top when the carb is turned upside down. Have seen them put in backwards many times. Heck, I've accidentally done it.
 

Greg Boswell

Seaman Apprentice
Joined
Oct 19, 2012
Messages
46
Re: 77 Johnson 115 won't hole shot without choke

I got my carbs confused with my other two-stroke carbs. Yes, these do not have adjustable needle valves. Sorry for that confusion. I did make sure to check the float levels and keep them even. Remember I had one that got out of control, but eventually I figured it out and the floats are in the correct position and move freely. I did check the needle and seats to be sure they sealed. I think the guys did an alright job on them. I did have them replace the throttle and control cables as they were original and they were reasonable cost to replace for me. I m wondering if the timing could have been changed and is why it seems to be running slow unless it gets the choke pushed??

I did get a break and we took it out late yesterday. Tried squeezing the fuel prime bulb, but that didn't make any difference. Just pushing in the choke button is all that I can do to get it to wake up. So, wait if the bulb squeezing didn't make any difference, does that mean my fuel pump is doing its job, the carb bowls are full??? hmmm?

The fuel pump rebuild kit is from this site. Sierra #18-7820 is what I used on mine. The pump kind of looks like this one from Sierra #18-7352. Not finding one for a 115hp at the moment.

The thing is that the engine ran better before I took it in for service and tune up. There must be some crud that got loosened up and has clogged the upper passages you mention. Although can't really see that since it always ran so good before and was always kept clean and used clean fuel and oil mix, changed filter regularly... Maybe, I need to replace the pump, eliminate that potential problem, go back through the fuel lines (they were old and sticky, might have let some deterioration loose inside?) and vacuum lines, and pull the carbs off again and see if I can figure out why (check the main and idle jets sizes for sure) I'm not getting full flow like before. Actually, you guys making me think they did replace the jets with smaller ones. I'll research and get the jet size then pull one out of a carb bowl. I believe there is one that that I can pull the bowl plug and get to the jet without taking time to pull the carb off just yet.. Not a big job, just can't take time at the moment, need to get back to work.
Thanks, it is helpful to get your input and advice. I appreciate it very much!

Thanks,
Greg
 

fireman57

Captain
Joined
Aug 24, 2004
Messages
3,811
Re: 77 Johnson 115 won't hole shot without choke

that jet takes a special size screwdriver or your will screw up the jet and not be able to get it out. squeeze teh primer until firm and then undo all the drain plugs and see if one bowl is empty or has a lot less than the others do. Your fuel pumpis fine, don't spend the $ replacing it.
 

Greg Boswell

Seaman Apprentice
Joined
Oct 19, 2012
Messages
46
Re: 77 Johnson 115 won't hole shot without choke

OK, thanks. I thought I had already taken the main jets out. Don't remember if I looked at the idle jets.
I may just wait until I can pull the carbs off and see what I'm doing them. Would hate to butcher the carb body or a jet.
Thanks,
Greg
 

Pat2009

Cadet
Joined
Aug 4, 2009
Messages
7
Re: 77 Johnson 115 won't hole shot without choke

DId you check the carb lingages to make sure they were tight and move the choke plates and butterfly plates in sync and to the right position.
 

emdsapmgr

Supreme Mariner
Joined
Dec 9, 2005
Messages
11,551
Re: 77 Johnson 115 won't hole shot without choke

If you constantly prime the fuel hose bulb while the engine is running (at higher rpm's) and it makes no difference, the pump is probably ok. The original fuel hoses on that engine are not rated to handle today's ethanol fuels. If you have any original hoses left under the cowling, they are suspect. Original hoses will break down and it's possible that black bits of hose can migrate down the fuel system into the jets in the carb, effectively restricting them. Best to replace any original hoses-ditto for the main fuel tank hose.
 

Greg Boswell

Seaman Apprentice
Joined
Oct 19, 2012
Messages
46
Re: 77 Johnson 115 won't hole shot without choke

New control cables installed at dealership. I would hope they sync'd them, but I did not know that could be a potential issue. Looking at the linkage between the carbs, I can't see how they are adjusted, Thanks, something to look into. but I'll read up on it and see if there is some way.
These carbs have no choke plates, the engine uses a fuel primer solenoid to squirt fuel into carbs for cold starting. That is what I push to get it to run right. Blip it at lower RPM's while at idle and just hold it in to take off and go full speed.

The fuel lines were all replaced at same time from the fuel tanks to the carbs including all the fuel lines and vacuum lines under the hood around engine. That was the reason I removed carbs again and cleaned them, I thought there might be something left over that was clogging them up, but it made no difference. Thought maybe it was moisture in the fuel (Florida), so installed a fuel/water filter, but that made no difference and like I mentioned, the fuel is clean. I totally cleaned both fuel tanks when the dealer was doing their thing. New lines, squeeze bulb, filter...

Beginning to think that since the motor is a 1977 115hp, and was a used rebuilt that I bought to repower up from a 70hp. Maybe this old motor is just tired and has given its best. I think that between what I paid for it and what I've put into it, I could have almost bought a new one by now LOL.
 

Greg Boswell

Seaman Apprentice
Joined
Oct 19, 2012
Messages
46
Re: 77 Johnson 115 won't hole shot without choke

Could it just be the thermostat has failed open and the motor isn't getting up to temp?...

Been trying to read through others issues having hole shot troubles, but seems like mine has had about all it can have done to remedy the issue. I must still be missing something.

The rectifier was in need of replacement per the mechanic, so I bought one and put it on, but no longer seeing my battery charging. Can't see how I could have installed it wrong. It was a very simple plug and play color coded harness and a few screws. Must mean the generator has crapped out. Wonder if that is causing my coils to not spark as hot as they should. Still, everything comes back to its not getting enough gas based on having to push the key and shoot gas in. I guess that indicates wrong jet size then. I'll call Monday and see if I can get an answer on if they changed jets. Doubtful that they will remember as I had all this done back in February.
Crack the manual open tonight and see if I can figure out the jet sizes. Thanks again for all the input. It is helpful, everyone.
 

emdsapmgr

Supreme Mariner
Joined
Dec 9, 2005
Messages
11,551
Re: 77 Johnson 115 won't hole shot without choke

Something is amiss here. Your engine may not be what you think it is. In 1977 the factory carbs came with choke butterflys which were activated by a solenoid with a plunger connected to the choke plates. Mid-year 1983 OMC changed their carbs to the fuel primer system and did away with the choke plates. Either your engine is not a 1977 model, or someone has changed the 1977 carbs to those from a much later engine. When carbs are swapped from one year engine to another, it is not unusual to wind up will running problems. Carbs are designed and jetted to make specific hp on a block. Mixing carbs on a dissimilar blocks an cause lean running or rich running. You really need to backup and re-valuate those carbs. From what you've indicated the engine is already running lean-which is not good.
 

Greg Boswell

Seaman Apprentice
Joined
Oct 19, 2012
Messages
46
Re: 77 Johnson 115 won't hole shot without choke

I see, well that makes sense. I bought the motor from a re-builder. Very likely he used what he had available to put motors back together. I think based on the block and thePrestolite trim and tilt which is from 1977 is why I keep referring to it as one. That and it was sold to me as a 1977. There was a little boat shop in town, operated by a couple of Vets. I think they must have re-re-retired. Have not seen them in years. But, when they first put this motor on my boat, it was a real beast and always ran flat out, almost too fast sometimes. I don't have a speedo, but it would easily keep up with traffic going across the bridge. The cars on the bridge generally travel around 55mph. It always had a leaky nature that was bothersome, never affected how well it ran, just always made a bit of a sheen on the water when sitting idle. This was the whole reason I took it in for a carb rebuild. Would have taken back where I bought it, but they were gone, the shop was gone and a new building was sitting there. I went through the phone book and online to see if I could find them, but since they were elderly, I think either one or both may have passed away or just gotten too old or too tired to run the shop any longer. Great old guys, always had a good story. They had this old VW rolling pan, just the pan, no body that they used to move boats around the shop with. Anyway, I am sure you are right about the mis match of carbs to block. Soon as I get caught up, I will pull the carbs off again and dig out the jets and see what size they are.
Good to know I did alright on the fuel pump rebuild. I had been wondering if that was my trouble.
I don't remember the dealer mechanic mentioning that my carbs were a different year than the motor. There was some conversation that I may have either a 1976 or a 1977 motor. Unfortunately, the serial plate on the side of the shaft housing has long been wiped clean from years of use and washing the motor. Is there some other place on the motor I can get a number to tell what year it is. Would be nice to know for sure. I could take pics and email them if you think that would help too. Should be able to upload some pics here I would think. Thanks for the help, I certainly do appreciate it. I know its an old motor. I have had it a long time and kind of attached in a way. I wish I had just lived with the leaky carbs, it ran so well, should have just left it alone. Oh well, live and learn..
 

Greg Boswell

Seaman Apprentice
Joined
Oct 19, 2012
Messages
46
Re: 77 Johnson 115 won't hole shot without choke

Got some photos. Maybe this will help some. Thanks a million for all the help
 

Attachments

  • 033.jpg
    033.jpg
    91.5 KB · Views: 0
  • 034.jpg
    034.jpg
    136.5 KB · Views: 0
  • 035.jpg
    035.jpg
    109.6 KB · Views: 0
  • 036.jpg
    036.jpg
    135.4 KB · Views: 0
  • 037.jpg
    037.jpg
    84.1 KB · Views: 0

fireman57

Captain
Joined
Aug 24, 2004
Messages
3,811
Re: 77 Johnson 115 won't hole shot without choke

A picture of the engine cover if it is original would help some too.
 

Greg Boswell

Seaman Apprentice
Joined
Oct 19, 2012
Messages
46
Re: 77 Johnson 115 won't hole shot without choke

Here you go. Hope this gives the view you need to see. Thanks
 

Attachments

  • 031.jpg
    031.jpg
    59.6 KB · Views: 0
  • 032.jpg
    032.jpg
    76.8 KB · Views: 0
Top