77 115 hp, no power

[wgolz]

Motor Specs: I have a 1977 115 Johnson V-4.<br /><br />Symptoms: Starts and idles well but would begin to lose power after warm up (WOT = 5500 if I remember correctly, since its been awhile since I was able to get it on plane).<br /><br />Compression: Cold (warm) compression is 130 (125) in cylinders 2 & 4, on the port side, and 135 (135) in cylinder 1 with 115 (115) in cylinder 3, 1 & 3 are starboard side. Squirting oil in the cylinders causes more than a 20 pound jump in compression in each cylinder. <br /><br />Spark: When I pull the plug wires on 1, 2, or 4, there is a noticable miss, but pulling the wire on cylinder 3 has no effect. There is spark to cylinder 3 and switching the coil leads and plug wires with cylinder 1 makes no difference (i.e., either way, it still stumbles when the number 1 wire is pulled but no difference when the number 3 wire is pulled). <br /><br />Questions: Is there anything else that I can try to remedy the problem short of a new power head?

 

[Walker]

Re: 77 115 hp, no power

Your compression numbers sound okay to me. # 3 is a little lower but should not make the engine run bad. I'd tear down the carbs and do a thorough cleaning and put fresh sparkplugs in her and give her a try. Check full system from tank, hoses, bulb, fuel pump. Make sure pump is working correctly and no fuel leaks or restrictions in the entire system.

 

[wgolz]

Re: 77 115 hp, no power

Walker, thanks a bunch for the advice. I will take a look at the fuel pump and start tearing the carbs down tomorrow. <br /><br />Forgot to mention it, but I removed and cleaned the tank, changed all the hoses and the bulb, and installed new plugs.<br /><br />By the way, its revs up fine with the muffs on, but when I put it in the water and give it some forward throttle to get it up on plane, it sputters and dies.

 

[captain spike]

Re: 77 115 hp, no power

just my opinion.....bill,are your carbs adj???have you done decarb?just a couple of things to do or check.tank vent open??<br /> <br /> *** 1971 18' winner 1969 115 jonny***

 

[wgolz]

Re: 77 115 hp, no power

Thanks captain spike. These are all good pointers. The carbs and throttle linkages were well adjusted just before the motor started losing power after it warmed up. I didn't mention it in the post but I just did a decarb with Deep Creep (i.e., spray Sea Foam). The tank is a welded aluminum 18 gallon with a permanent 5/8" hose vent which is working well, and although I did not mention this in the post either, I just took the tank out this week and did a complete rinse down and reinstall with all new fuel hose, filter, bulb, etc.

 

[wgolz]

Re: 77 115 hp, no power

Update: Following Walker's advice that it may be a fuel problem, today I decided to try power flushing the carbs before doing a complete rebuild: to do this, I got the motor running and then dropped the hose into a bottle of pure Gumout carb cleaner; then, after letting that sit for about five minutes, I removed the plugs, disconnected the linkage, propped the throttle wide open, and ran gas through the carbs, blowing it out the exhaust and the open plug holes, being careful not to overheat the starter. I also sprayed B-12 down the carb throats, with the silencers and front cover off. <br /><br />Result: It started running on all four cylinders, but when I put it in the river and gave it gas, it died. So I tried choking it, and it sputtered, but I was able to get it up on plane. Then, it ran fine for an hour up and down the river, varying from idle all the way to WOT.<br /><br />Questions: <br /><br />1. I don't have any idea why it went from dying to running great after I choked it up onto plane. My only guess is that I had a stuck reed valve or something caught in the carb and choking it pulled the reed valve loose or made the carb pass the debris through the engine. Any ideas?<br /><br />2. I thought about running liquid B-12 in the cylindrical 16 oz. metal can through the fuel hose into the carbs, instead of Gumout. B-12 is quite a bit more potent as a solvent than Gumout, so I was wondering if anyone had any opinions on whether or not B-12 would do any damage like eating carb or fuel pump gaskets.

 

[Walker]

Re: 77 115 hp, no power

It won't eat any components but it has no lubricating qualities at all and if you run it throught the carbs full strength you wll be running your bearings and piston ring dry for a short time. Not good.

 

[Hooty]

Re: 77 115 hp, no power

Walker's right, plus, runnin' that caca through your carbs don't do jack for 'um. They don' plug up where that stuff goes.<br /><br />c/6<br />Hooty

 

[wgolz]

Re: 77 115 hp, no power

Thanks again for the helpful advice Walker. <br /><br />I ran a Seafoam (16 oz)/Gas (48 oz)/Oil (1.3 oz) mixture through at fast idle for decarb.<br /><br />I ran a 24:1 Gumout:Oil mix through the carbs and power flushed them again.<br /><br />After some more running, it showed some symptoms that are consistent with a bad fuel-pump diaphram, so will change that tomorrow.<br /><br />I'll let you know how all this finally turns out.

 

[Solittle]

Re: 77 115 hp, no power

Bill - Power flushing and running this or that through the carbs is not a substitute for a thorough cleaning and rebuild.

 

[wgolz]

Re: 77 115 hp, no power

The fuel system is A-OK: checked everything, changed the fuel pump, and went through the carbs.<br /><br />Intermittent problem persisted: runs fine for awhile, 4500 WOT and then it will barely get up on plane, 3200 WOT. The spark on number 3 was a little weak but is now no spark. Tried switching the coils at the power pack with a corresponding change in the plug wires. Same problem, so it is not the coils (earlier, I checked all the grounds and switched the port and starboard coils).<br /><br />Question: <br /><br />Is this a likely sensor problem? The sensors are part of a timer base ($300). Otherwise, could it be a power pack ($97)? The power pack seems unlikely to me though, with the spark missing on only one cylinder?<br /><br />What would be the best way to narrow down the diagnosis, so I don't end up with a big ($397 + tax) bill for a trial and error change of parts?<br /><br />Any thoughts?

 

[BKool68]

Re: 77 115 hp, no power

Bill try switching the powerpacks from side to side. If the problem cylider moves that is your problem. If the no spark stays it would suggest a stator problem. As far as carb cleaning goes there is no substitue for soaking them for at least an hour in carb solvent.<br />Brian

 

[wgolz]

Re: 77 115 hp, no power

Brian, <br />You must be thinking of the 1978-84, 4 cylinder motors which have two identical ignition systems, one for each side. My motor is a 77, the year before the change, and has only one power pack.<br /><br />I don't have enough experience to trust my gut feeling that it is a power pack and I don't have access to the special neon tester required to diagnose the problem. If there is another way to single out the power pack, or to test the system component by component, using a volt/ohm meter, I would like to try it.<br /><br />Thanks for the thoughts Brian.