1965 johnson 40 hp sudden power loss

[dafox99]

Guys,<br /><br />Well, was having a wonderful morning in the old '58 texas maid when suddenly, I went to half power. some clues:<br /><br />* New plugs<br />* Need to de-carb motor, but lost my can of sea foam. The old plugs had carbon on them.<br />* It's not dropping a cylinder as I can pull either plug wire (yes .. alone in boat pulling plug wires while going down the lake) and it still runs<br />* since I didn't have my sea foam handy, I put a can of merc quick-clean in the tank. I switched tanks after losing power .. no dice<br />* Here may be the kicker - my well-intentioned buddy decided to spray some carb cleaner into the bowl via the high speed jet (I had the cap screw off) only an hour before we took off. <br /><br />I've typically thought that last bullet was bad as the cleaner can eat up items in the carb. I stopped him, but too late. The boat ran like a striped ape for about 45 minutes before I lost the top end. It runs pretty good up till the cross-over where the high-speed takes over then just bogs.<br /><br />I don't have the right flywheel puller, so will be just dropping the bowl to do a quick carb check until I get the right pull-bolts, but I don't have a carb kit anyway.<br /><br />All ideas welcome.

 

[Goodoleboy]

Re: 1965 johnson 40 hp sudden power loss

Dave!....I would be highly suspious of an air leak in the fuel lines.<br /><br />Check for broken clamps, cracked hose's, check oring seal at tank connection and at engine.<br /><br />always look for the simple things first. If you dont find any thing suspious with the fuel lines then I would do a quick check on the timeing, Just so id know for sure its ok.<br /><br />If all this checks ok, Then you have likley got some trash in the high speed jet or jets's in the carbs.<br /><br />Good luck!

 

[Paul Moir]

Re: 1965 johnson 40 hp sudden power loss

Pumping the primer bulb will point out an air leak / problem fuel pump. If the engine starts running better or worse when you pump it, you've got a fuel supply problem. If everything's ok then all that's likely good.<br /><br />Did you run fast with the spark plug wire pulled? If not, you could still have a spark failing under load. How do the spark plugs look? If they're ultra-clean, you may have blown a head gasket. (EDIT: Unlikely, it wouldn't run well at any speed...) If they look a little lean, try partly choking the carb with your hand. If the engine picks up, a cloged high speed jet is likely.

 

[CATransplant]

Re: 1965 johnson 40 hp sudden power loss

Hmmm....you pulled the plug wires after it went to half power?<br /><br />That's odd. Usually, these sudden half power things are a loss of spark. If the engine ran on both plugs, though, I'd be looking at the fuel system. Maybe the carb, but also maybe something else in the fuel supply system.<br /><br />How does it idle now?

 

[dafox99]

Re: 1965 johnson 40 hp sudden power loss

Team (yes, you are now officially my 40 hp team),<br /><br />Idles good.<br /><br />Since I trotted downstairs after authoring this, I pulled the carb, pulled it apart and cleaned it (jeez .. gotta pull starter and generator to get to it). not much cleaning to be done, however, as it was pretty darn good. Needle/seat worked good, float at proper level, high speed seemed fine. The fuel line from the pump to carb broke off in my hand at the carb clamp. Replaced line.<br /><br />I tried pumping bulb under power when I was on the lake .. no dice.<br /><br />I also tried partial choke while running to see if richening it helped. Notta.<br /><br />Beginning to suspect fire per your comments. I pulled the wires at low speed when on the lake as to not kill me or other boaters (no one at the helm). <br /><br />After cleaning carb, I pulled the plugs. One looked good, while the other was a bit black. Also, while at the lake, I pulled the controls and revved engine in neutral a bit .. seemed to rev pretty high pretty fast.<br /><br />So assuming I fixed nothing, what causes new plugs to fail under load? Sometimes I remember hearing a "clicking" under the flywheel when coil cracked. I don't hear that now.<br /><br />thanks

 

[Goodoleboy]

Re: 1965 johnson 40 hp sudden power loss

Your new plugs probably arent failing under fire. You may not have a strong enough spark however to withstand the compresion and fuel/air mixture in the cylinder.<br /><br />Gota check and see if spark will jump a 7/16 gap. Yep its spark tester time.<br /><br />you can make one or you can run down to the auto parts store and by one for ten bucks or so. they are mitey handy to have around.<br /><br />Paul Moir has a picture of the the one he made purty slick setup to. Dont cost nutin!<br /><br />Good luck!

 

[dafox99]

Re: 1965 johnson 40 hp sudden power loss

Cool. Waaaayyy back, we had one made of nails that hit a center post and we would move the nails in.<br /><br />So .. if it's not enough spark, and it just suddenly started doing this ... bad coil?<br /><br />Thanks again

 

[CATransplant]

Re: 1965 johnson 40 hp sudden power loss

As Paul has pointed out several times, these Big Twins don't always make a spark that will jump 7/16". Mine sure doesn't.<br /><br />Still, half speed suddenly is usually an ignition symptom. A could could have failed. Points might not be opening sufficiently. <br /><br />And, yes, brand new spark plugs have been known to be bad.

 

[dafox99]

Re: 1965 johnson 40 hp sudden power loss

Okeedokee. Well .. in a band .. playing a gig tonight. Will let you know what I find when I get back on it. thanks for all the help!

 

[dafox99]

Re: 1965 johnson 40 hp sudden power loss

OK, guys. How about this: I get another guy in the boat with me (we live on the lake, so going to the lake is not a problem), I take the cowl off, and have him drive at WOT. Assuming I've fixed nothing, it will only run about 15 mph. I'll pull a plug wire and see if I'm still running on two, or if I dropped one under load.<br /><br />I think I have Champion J8C plugs. any idea what the gap should be?<br /><br />Also .. any chance this is a heat related coil failure? It ran great for over an hour and then this problem came up. I remember coils cracking and firing to ground, but I'm not sure if they did it just at high speed, or all the time. Just trying to figure out what's broke and why. I guess I can pull the flywheel and do a visual on the coils. <br /><br />Do all you guys have flywheel wrenches for holding the flywheel while torquing, or does anyone else use the old "big screwdriver" method to hold that sucker? I've heard not to do that as I could break something like a flywheel tooth ro whatever I am holding the screwdriver against for leverage.

 

[Paul Moir]

Re: 1965 johnson 40 hp sudden power loss

Sounds good. You can also try getting it started on one cylinder and taking off. A little tricky though.<br /><br />J8C ought to be too hot. J4C (standard) or J6C are the options. Perhaps that's what's causing the trouble. Gap is .030" regardless.<br />What's been done with the igniton system? If they're new coils, I doubt their the problem. How about the wires? No cracks in the insulation, etc? I take it the advance is going to it's stop correctly and the carb is opening wide (not a linkage problem).<br /><br />Although now I have a flywheel wrench of sorts, I've got good results by jamming the electric starter with a peice of soft metal (so as not to mar the teeth).

 

[dafox99]

Re: 1965 johnson 40 hp sudden power loss

Paul,<br /><br />I just bougth this boat a few weeks ago, and it had J8C's in it. My local boat shop's books or software doesn't go back far enough, so I replaced with what was in it. I still need to de-carb as the old plugs had carbon on them, but I LOST my can of sea foam. Hopefully will get that done in a day or two. Also, under the advice of the hardware store I got the plugs (boat shop and auto shop didn't have them), I gapped at .040.<br /><br />I'll get some J4C's unless you think the 6's are better and gap to .030. Can too hot of spark cause this? Would be nice if this is all it is.<br /><br />I have not popped the flywheel to look at the coils, but the wires look good, and not brittle or cracked.<br /><br />with a little mirror and flashlight, it looks like the cam is hitting the the timing plate at the line (didn't pull the flywheel yet), the advance goes full and the throttle plate is completely open.

 

[Paul Moir]

Re: 1965 johnson 40 hp sudden power loss

If you can draw a 3/8" spark, likely the ignition system is fine. On a hunch I would try the same test at both start speeds and full throttle. <br />There's an error on the current Champion spark plug chart that suggests J8Cs for this engine. J4C is the normal plug while the J6C can be good if you do a lot of idling/trolling. I guess hotter plugs are important at altitude too but I'm no expert on that since my part of the world doesn't have altitude. <br />Try the plugs you've got at the right gap though. The ignition system isn't the strongest afterall, and it'll have troubles firing wide gaps under compression.

 

[dafox99]

Re: 1965 johnson 40 hp sudden power loss

OK, guys, let's recap. Maybe this is like one of those crime shows where the extraneous people leave out a pertinent clue, and suddenly one of them remembers the perp was having an affair with the dead guy's wife. Here's all the clues I've got:<br /><br />* Bought boat/motor a few weeks ago<br />* Ran pretty good first time out, but seemed to surge a bit at top end.<br />* Last time out, a buddy sprayed carb cleaner in bowl through high-speed opening in bowl. I also had a bottle of merc "quick-clean" in the tank at the time.<br />* Ran great for about an hour. sudden power loss .. about 1/2 throttle.<br />* New plugs. First new plugs were too hot (J8C). Put right new plugs in yesterday (J4C).<br />* Took carb apart. Looked great. Float at right level, needle/seat seemed to work fine. Blew out high speed. No sediment.<br />* Link/sync looks A-OK. Roller hits at the right place, timing goes to stop, and throttle plate opens completely at WOT.<br />* Just took it out. Same problem .. 1/2 power.<br />* Had my complaining, but trusty daughter with me this time after bribing here with starbucks, so I was able to:<br />* Pull plug wires at WOT. Both running fine. So good, the spark dang near sterilized me .. man, it has a kick. I didn't have the fancy plastic plug wire pullers. At one point, it died, wouldn't go, I pulled lower plug clear out, and placed on motor. It started and ran on the other while this external plug was firing just fine. I think it was fouled in cylinder. I swapped plugs, wiped them off and they both hit again.<br />* Pumped bulb. No change<br />* Pulled bowl high-speed cap screw. Bowl had plenty of fuel.<br />* New gas<br />* Have not done decarb yet<br />* Choked while running. No difference<br /><br />So .. in conclusion:<br /><br /><br />* Ran great.<br />* It suddently runs at 1/2 throttle. <br />* Carb looks pristine, but did not put a kit in it .. just cleaned it.<br />* Have not run compression check yet. Need to get compression gauge.<br />* Seems to fire fine at idle through WOT.<br />* Link/sync seems OK<br />* did not have a spray bottle, so have not tried the "spray pre-mix down carb while running" thing yet.<br /><br />So, assuming I didn't suddenly lose compression in both cylinders (seems to run about the same regardless of which plug wire I pull) while just running down the lake, and fire seems great, either some nutty vacuum or fuel issue still? Reeds seemed OK with just a visual through the reed plate with carb off. I once had a semi-loose reed plate that caused a similar symtom<br /><br />It's killing me. Begining to consider offering reward to first guy to fix it ... just like the crime shows.

 

[CATransplant]

Re: 1965 johnson 40 hp sudden power loss

Well, OK, you have good spark, since it runs the same with either plug wire off. You have the right plugs now.<br /><br />But it still runs lousy at high speed. I'm thinking fuel system now. No change when you pump the bulb and fresh fuel in bowl. Choke didn't make a difference.<br /><br />I'm betting on a partially clogged high speed jet on this engine. The boat's new to you, so there may well be crud in your fuel tank or accumulated crud in the lines. It happens a lot.<br /><br />I'd add an in-line fuel filter on the engine side of the bulb. Use one of the big auto types you can see through...they allow plenty of flow.<br /><br />But...I think the carb's going to have to come off and get that high speed circuit cleaned out. I'm betting that once you do that, you'll be back in business.<br /><br />The only other thing I can think of is a defective fuel pump, which could also cause this symptom if the diaphragm is holed, by allowing too much fuel mix to get into the crankcase. That doesn't seem likely, since the engine runs fine at low throttle settings, though.

 

[dafox99]

Re: 1965 johnson 40 hp sudden power loss

Sounds good. I did fire carb cleaner though the high speed just yesterday before putting back together, but these tanks could clearly be full of crud.<br /><br />I'm off to the auto store for the in-line. think I'll get a new bulb while I'm at it from the boat store, since mine doesn't seem quite as sturdy as I'd like. Clearly, someone did something with the fuel pump at one point as I can see a fresh gasket. I think it's pretty simple to pull those four screws and just check for a hole in the diaphragm .. yes? Maybe if there is a hole, it might be more of a vacuum leak issue than not-enough-fuel issue since my carb seems to have plenty of fuel?

 

[Paul Moir]

Re: 1965 johnson 40 hp sudden power loss

You ought to have the new style pump. It's held to the block by two screws, right? Just remove the pump and pump up the primer. If it doesn't leak out the back, the pump diaphram is good.<br /><br />Now, this ought to have been ruled out as a possibility when you pumped the primer bulb while running high speed.<br />Just to be certain, you are cleaning the high speed oriface (in the bottom of the carb bowl) not the high speed nozzle which runs up into the throat of the carb right?<br /><br />PS - The very best fuel line components to be found on the earth are at your local Johnson/Evinrude dealer, IMO. Great fuel line/bulb/connectors compared to others.

 

[CATransplant]

Re: 1965 johnson 40 hp sudden power loss

Careful with that fuel pump. It's kind of a bear to reassemble. If it has a fresh gasket, you might want to assume that it's OK and leave it alone for now. One thing at a time.

 

[dafox99]

Re: 1965 johnson 40 hp sudden power loss

Six screws through the pump, two of them attaching it to the block. I'll take it off the block and see if it leaks while pumping. Don't think I'll take apart at this point.<br /><br />I sprayed new can (pretty high pressure) of cleaner through oriface in bottom of bowl as well as well as the nozzle. I took the nozzle out, but not the oriface as I have seen guys mar the surface of the oriface if they don't have the right screwdriver. I did put that long red straw that comes with the cleaner right up to the oriface and blast it. The cleaner clearly came shooting up out of the nozzle (instead of the through the pickup in the bowl), so the high speed should be clear. Yes? The (crappy) boat shop next to my house should have the OMC pump and line.

 

[dafox99]

Re: 1965 johnson 40 hp sudden power loss

OK ... it's #1. but still not sure why.<br /><br />Checked fuel pump. No leak. didn't expect any as bowl always seemed full<br /><br />Put flushette on (no help in site).<br />Ran with #1 out and could rev it up quite a bit<br />Put #1 back in and ran with #2 out. After about 2/3 throttle, it hits a rev wall and just won't rev any more ... just like in the water.<br /><br />New theory ... ignition .. right? One carb feeds both cylinders. What would keep a coil firing, just not advance as the motor keeps running, just stays at the same rpm and sputters and misses. Just for thoroughness, I swapped plugs and the result is the same. <br /><br />My next move ... pull flywheel and have a look-see at #1 coil?<br /><br />Please advise. I'm running out of brain cells