4hp johnson 1977

[chuck4080]

I have much trouble trying to start and keep running (new to me) johnson 4hp 1977 motor. Disassembled the fuel pump, look clean, but only one spring, put it back together w/o springs. disconnected plug wire from bottom cyl and eng. died. Did comp test. Top cyl 68psi and bottom 70psi. Not sure if comp is high enough. Both cyl get good fire. I will now try decarb, then head gasket, then carb. I think I have read everything on this forum (lots of help) is there anything else I should be trying before it goes into deep six. Thanks Chuck

 

[Lostreb]

Re: 4hp johnson 1977

I have the same engine on my little fishing boat and it is also having some starting issues. I have checked the same things you have to no avail. My next step is going through the carb with a fine tooth comb. I should have already done it, but haven't yet. Make sure the points, cap and condensors are good also. Just because it sparks does not mean it's right.

 

[Lostreb]

Re: 4hp johnson 1977

Now I feel like a complete idiot here. Anyone that has EVER taken an outbaord apart knows there is no cap. Overlook my stupidity and just doublecheck the points settings. Also make sure the magneto is clean. I would also make sure the key that holds the magneto is not distorted in any way, even a little can upset the timing.

 

[Rick.]

Re: 4hp johnson 1977

I would not be overly concerned about the compression. I think it will improve once you get it running and do the decarb.. Sounds like a new fuel pump is in order. I would get a new kit for the carb. and give it a very good cleaning. With that and the fuel pump you should get it running well enough for a decarb. Great little motors they are. Best of luck. Rick.

 

[chuck4080]

Re: 4hp johnson 1977

Lostreb & Rick, Thank you for the reply and suggestions. I did a so, so decarb on the motor. Had the boat tied to the dock and ran it for about 45 minutes at or near top end. Smoked up the marina. It started and ran pretty good. I pulled the plug wire on the good cyl and motor kept running for short while. I even started it up and ran on the bad cyl. Motor will run out of fuel after about ten minutes, can squeeze bulb and it will start up again. So I guess next step is to replace $90 or rebuild fuel pump. Maybe even carb. I am very encouraged after the decarb. Thanks for this forum and your help. Chuck

 

[Lostreb]

Re: 4hp johnson 1977

I'm no expert here, but it doesn't sound like the pump. If it were, then it would not run 45 minutes when both cylinders were running, and only ten when the good one was unhooked. The fact that it ran longer when both were running rules out a lot of things, such as the pump, carb. First, check the points settings, since each cylinder runs off a dedicated set of points and condensor. The gap may be slightly off on the cylinder that is not running well. While you're at it, go ahead and replace BOTH sets in there, they don't cost much and it will eliminate that possibility. Then my next move (if that doesn't fix it) would be to replce the rings on the pistons now. My bet is it's something in that one cylinder that ran ten minutes, then you had to re-pump the bulb.

 

[chuck4080]

Re: 4hp johnson 1977

Lostreb: What you are suggesting may be correct. Since I was getting good fire at both plugs I discounted electrical. Unfortunately I have ordered kits for FP and Carb. Wish I had included the points. I am going to go ahead and install the kits and see what happens.....and then go for the points etc. But you know, that decarb has really done wonders for the motor....wish I could do similar thing on my wife....just kidding!! Chuck

 

[Rick.]

Re: 4hp johnson 1977

It seems to me this thread is all over the map. Why do you refer to one cylinder as good and the other as bad? If it is the two pounds difference in your compression forget about it. For the sake of two pounds you can refer to them both as equals (good or bad). You said you left the spring out of your fuel pump so the rebuild is a must in my opinion. Be very careful putting the kit in or it will not run regardless of the new parts. Everything must line up and be in perfect order or you could stop fuel flow all together. Glad to here the decarb went well. Once you get it running for a bit I would like to know if your compression improves. It sure did with my 71- 4HP. The carb. kit will not be a waste of money or your time. Rick.

 

[Lostreb]

Re: 4hp johnson 1977

Sounds like you're well on your way to having a good running little engine. However, I can offer nothing concerning your wife. I have one here that I am still trying to get figured out, lol.
Let us know how the kits work.

 

[chuck4080]

Re: 4hp johnson 1977

Rick: you are right, "its all over the map" cause I don't know what I am doing. About the cyl. before decarb it was only running on one cyl (took plug wire off and motor would go dead), took other plug wire off and motor would continue to run. After decarb, would run equally well on either one cyl. As for the FP apparently someone in the past left one of the springs out, plus no caps for the one spring. It is very surprising that the poor motor even runs at all. The kits have been shipped but it will be about a week before I can install. I will keep you posted. An't these forums fun and more important helpful! Regards Chuck

 

[chuck4080]

Re: 4hp johnson 1977

Update on my 1977 4hp Johnson: Took the fuel pump apart and found a diaphragm gasket with a 1/2" tare. It is amazing the motor even ran, both springs missing and torn diaphragm. Installed a kit, and motor runs like a new one. Would start after 1st or second pull. Ran the motor off and on for about 45 minutes. Took it for a ride, about 30 minutes. Ran just great. Then all of a sudden it sputtered and died. Felt the motor it was hot. Let it cool down, and tried to start. Nothing, I guess it is toast. Question: how can I tell if it is burnt up and done for??? Thanks Chuck

 

[Rick.]

Re: 4hp johnson 1977

Well I don't much like the second part of your story. Unfortunate. Best thing now is a compression check. Let us know what you find. You may well need a new head gasket at this point but check compression first. Rick.

 

[chuck4080]

Re: 4hp johnson 1977

Rick, seems I am locked in a never ending story. Took the motor home did a compression test. It actually was a little better than previous test 75 and 73. Encouraging, started on the 5th pull. The water exhaust is not much, sort of spits and twinkles, but the water is not hot. So decided go ahead with new carb kit. Half way into it. Some bad parts and crud. If I get it back together ..big question. Maybe it will be okay. Would really like to see the old thing run. Hope the ole motor and me still have a few more kicks left. Regards Chuck

 

[Rick.]

Re: 4hp johnson 1977

Well sorry to say I'm probably more confident in the motor. LOL. I was thinking/hoping your compression will come up after a decarb. and some regular use. Glad you had your previous comp.#'s as a reference so we know the head gasket isn't leaking. They do just sort of sputter a fine mist out the back holes, nothing like a tell tale. Sounds like with the clean carb. your soon going to back on the water having a great time. Rick.

 

[chuck4080]

Re: 4hp johnson 1977

Rick: I am almost ashamed to respond. After much help from a friend, the carb rebuild was complete. Motor would start an run just perfect. The next morning I am eager to start the motor for another test. It would just not start after hours of trying different things. Decided to replace fuel line bulb (motor would not get gas). The motor started right up and ran okay but would slowly die after a few minutes. squeezing the new bulb I noticed gas leaking (slight leak) around fuel pump filter cover. The threads were bad on the set screw, so I have ordered a new one. Not sure if either the motor or I will make it. Regards Chuck

 

[chuck4080]

Re: 4hp johnson 1977

Thanks to everyone for advice and encouragement. Motor running great. Probably best help was the decarb and fuel pump kit. "Regards Chuck

 

[Rick.]

Re: 4hp johnson 1977

Congratulations Chuck. May you get many many hours of enjoyment from it. Rick.