Not sure about alot of stuff... 1963 75hp Johnson

[MrsFish]

Okay so the issue is a severely bogged down motor. I have had the thing running great one minute, then next time I start it it's a dog. Compression is 76 in 3 and 74 in the cylinder needing an insert. I have yet to check for "consistant" spark cause I had to helicoil one of the plugs (maybe this will solve the problem but I doubt it). Since I had the cylinder cover off the one side I figued may as well clean and re-gasket both sides. Pistons and cyls look good but alot of carbon. Anyway I suspect the following things are problems... First I have a water choke assembly?!?, choke never closes unless I do it manually. Second it appears that somebody changed out a venturi or a jet (same thing?) once upon a time and the #'s do not match. I would like to know how the venturis are supposed to behave? One of them is a slow drip and the other is about 5x faster of a drip, almost a stream. I eat fuel like you would not believe but I have no frame of refrence since this is my first boat. 1964 16' Glastron Skiflite that gets up and goes when it feels like it. It is getting embarassing though!!
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[tashasdaddy]

Re: Can somebody tell me how a venturi tube or jet is supposed to behave?

Re: Can somebody tell me how a venturi tube or jet is supposed to behave?

please read this, http://forums.iboats.com/showthread.php?t=250879. i have no idea what you are asking, although 76 psi compression is low on most motors.

 

[daselbee]

Re: Can somebody tell me how a venturi tube or jet is supposed to behave?

Re: Can somebody tell me how a venturi tube or jet is supposed to behave?

OK TD...I'll say it....

Wow...and you expect an answer...without even telling us what motor it is...
Amazing.
Here are the questions I have just by reading your cryptic post:
1. How many cylinders? Have to assume 4, but I don't understand the "76 in 3 and 74 in the cylinder needing an insert". 76 is too low, anyway.
2. What do you mean "insert"? Sleeve?
3. Cylinder cover....you mean the bypass covers?
4. Water choke? What is that?
5. Venturi change? I doubt it. Jet change, yes. The small screw in jets have numbers on them, and they are internal to the carb.
6. Dripping venturis? What the h...? Nothing is supposed to "drip".

Please post something understandable, starting with the model number of the engine...we don't care about the boat.

 

[MrsFish]

Re: Can somebody tell me how a venturi tube or jet is supposed to behave?

Re: Can somebody tell me how a venturi tube or jet is supposed to behave?

OK TD...I'll say it....

Wow...and you expect an answer...without even telling us what motor it is...
Amazing.
Here are the questions I have just by reading your cryptic post:
1. How many cylinders? Have to assume 4, but I don't understand the "76 in 3 and 74 in the cylinder needing an insert". 76 is too low, anyway.
2. What do you mean "insert"? Sleeve?
3. Cylinder cover....you mean the bypass covers?
4. Water choke? What is that?
5. Venturi change? I doubt it. Jet change, yes. The small screw in jets have numbers on them, and they are internal to the carb.
6. Dripping venturis? What the h...? Nothing is supposed to "drip".

Please post something understandable, starting with the model number of the engine...we don't care about the boat.

Okay, thanks for making me feel like a dumb ***!
Funny though since I actally got a response from somebody when I changed the posting title and forgot to put the motor back in the text of my questions.

So point by point:

1963 75hp Johnson
Magneto not battery ignition, type 1B carb, manual shift, v4 etc...

Has a WATER Choke not an ELECTRIC choke. Operates when the WATER gets HOT! (pretty basic)
One of the spark plug holes was nearly stripped so it got an INSERT sort of like a helicoil.
Head cover, cylinder cover whatever dude. Not bypass cover.
Yes it is getting 76psi which I think is enough because when this boat goes it really moves. But I'm not sure. Thus one of my many questions.
Sorry I'm not real carb savvy! Yes I meant JET not VENTURI. Anyway having a very crude understanding of a carbs JOB, I figured the dripping was not good. Furthermore that the two sides of the carb getting different amounts of fuel also not good. I believe you confirmed this however curtly but did not have a suggestion for what to do about this issue. The carb has been disassembled and cleaned immediately upon purchase due to the fact that the guy I bought it from said he got dry rot rubber particles in there from an old primer bulb.

Anyway I guess that if the only response I can get from here is a rude one I'm better off re-reading the manuals and staring over from the top. Spark test, compression, timing, link & sync...
Thanks anyway fellas!

 

[R.Johnson]

Re: Can somebody tell me how a venturi tube or jet is supposed to behave?

Re: Can somebody tell me how a venturi tube or jet is supposed to behave?

You don't need a service manual for venturi, you need a dictionary.

 

[asdasc]

Re: Not sure about alot of stuff... 1963 75hp Johnson

Don't give up on us yet. With a little patience and information, we can actually be very helpful. The folks on here are VERY good. I always try to post pictures with my questions, it helps to answer a lot of questions.

So, if it runs and runs well some or most of the time, I am guessing there isn't a compression problem. My guess is that when you took the readings, either it wasn't turning over fast enough, or there was some problem with the pressure gauge you were using.

Two things will rob your power - lack of gas or lack of spark (again assuming the compression is really not that bad). Either way, 1 or more cylinders is not doing it's fair share. We just gotta figure out which one, and why.

Have you ever checked for spark? It is pretty easy with a spark checker. You can get them for under $10 at any auto store. Insert it into the the plug wire after removing the plugs, and you should get a consistant bright blue spark when you spin the engine over pretty fast. It is VERY common on a motor of this age that it will need new coils/condensors/points. It will cost about $100 in parts, and take a couple hours, but it will renew your spark/ignition system to like new, and last another 50 years.

The carbs sound like they need to be rebuilt. I assume there are two? There are no reason anyone SHOULD have tried to change out a jet, but you never know. If you look in the TOP SECRET FILE, there is all kinds of good infomration on rebuilding the carbs and the ignition.

Read thru that, do a little more messing around, post a picture if you have specific questions, and you will be up and running like new in no time.

Good luck,

 

[F_R]

Re: Not sure about alot of stuff... 1963 75hp Johnson

Your carburetor jets (properly called "orifice plugs") should both be the same size. They are part number 309517 and should be stamped 72, neaning they are 72 thousandths of an inch in diameter. Of course some people think they are smarter than the engineers that designed it and drill them out thinking that will make it go faster. The only thing that goes faster is the gasoline. Speaking of that, I am not sure what you mean by the dripping. Exactly what kind of test are you doing to determine that?

I don't have to tell you that you only have one carburetor, you already know that.

Those hot water chokes were junk when they were brand new. Most people put them on automatic to start it , then flip it to choke off once it starts. It sounds like the bi-metal spring in yours may be shot, not closing it at all. Nevertheless, just manually choke/unchoke it and don't fret about it.

There ARE people here that can help you. Don't give up.

 

[MrsFish]

Re: Can somebody tell me how a venturi tube or jet is supposed to behave?

Re: Can somebody tell me how a venturi tube or jet is supposed to behave?

You don't need a service manual for venturi, you need a dictionary.

Um yeah thanks for being SO helpful!!

 

[MrsFish]

Re: Not sure about alot of stuff... 1963 75hp Johnson

Your carburetor jets (properly called "orifice plugs") should both be the same size. They are part number 309517 and should be stamped 72, neaning they are 72 thousandths of an inch in diameter. Of course some people think they are smarter than the engineers that designed it and drill them out thinking that will make it go faster. The only thing that goes faster is the gasoline. Speaking of that, I am not sure what you mean by the dripping. Exactly what kind of test are you doing to determine that?

I don't have to tell you that you only have one carburetor, you already know that.

Those hot water chokes were junk when they were brand new. Most people put them on automatic to start it , then flip it to choke off once it starts. It sounds like the bi-metal spring in yours may be shot, not closing it at all. Nevertheless, just manually choke/unchoke it and don't fret about it.

There ARE people here that can help you. Don't give up.

Thanks Mister.
So I figured the water choke thing wasn't too big a deal although it would be nice to not have to pull the motor cover off to choke the motor. At least you knew what I was talking about!
As for the dripping... No test per say, just looking in there and seeing the fuel is not atomizing at all. Is it supposed to IN the carb? I think this is why I'm going through tons of fuel. I will look at the jets tonight to see if they are the spec ones. I have a buddy who is GOOD with these motors (he's sick of me calling) who said changing the jets would bring nothing but great sadness. I think previous owner did that for me!! We'll see.

Again thanks!

 

[MrsFish]

Re: Not sure about alot of stuff... 1963 75hp Johnson

Don't give up on us yet. With a little patience and information, we can actually be very helpful. The folks on here are VERY good. I always try to post pictures with my questions, it helps to answer a lot of questions.

So, if it runs and runs well some or most of the time, I am guessing there isn't a compression problem. My guess is that when you took the readings, either it wasn't turning over fast enough, or there was some problem with the pressure gauge you were using.

Two things will rob your power - lack of gas or lack of spark (again assuming the compression is really not that bad). Either way, 1 or more cylinders is not doing it's fair share. We just gotta figure out which one, and why.

Have you ever checked for spark? It is pretty easy with a spark checker. You can get them for under $10 at any auto store. Insert it into the the plug wire after removing the plugs, and you should get a consistant bright blue spark when you spin the engine over pretty fast. It is VERY common on a motor of this age that it will need new coils/condensors/points. It will cost about $100 in parts, and take a couple hours, but it will renew your spark/ignition system to like new, and last another 50 years.

The carbs sound like they need to be rebuilt. I assume there are two? There are no reason anyone SHOULD have tried to change out a jet, but you never know. If you look in the TOP SECRET FILE, there is all kinds of good infomration on rebuilding the carbs and the ignition.

Read thru that, do a little more messing around, post a picture if you have specific questions, and you will be up and running like new in no time.

Good luck,

Thanks a bunch.
I too think the compression is okay.
I am putting the head covers back on tonight with new gaskets. I cleaned out all the carbon and it looks all good in there. Yes I have new points, distributor cap, rotor, condenser, plugs & wires. Not coil though. Guess I really should? I have checked for spark but not for "consistent" spark so soon as the heads are back on that's where I'm headed along with comparing the # on the jets that FR gave me.
I feel like I've messed with every major system in this motor short of the complete carb rebuild. Wonder what the kit will cost? Oh yeah and no sir, there is only one carb on this old guy.

 

[R.Johnson]

Re: Not sure about alot of stuff... 1963 75hp Johnson

I was not trying to be unhelpful, but every carb, has a venturi. You said your's leaked, If you know what it is, you know that is not possible. You want to throw around a term like you know what you are doing. Well then. fix your venturi. Better yet! replace it.

 

[Willyclay]

Re: Not sure about alot of stuff... 1963 75hp Johnson

OMC specified the use of a special tool for centering the orifice plugs in the carburetor throats after a rebuild. I have one of these tools from my many years with a 1962 Johnson 75HP. Will dig around in my parts bin and see if I can come up with a P/N for you. FYI, it's going to use a lot of gas even when it is perfectly tuned! Good luck.

 

[F_R]

Re: Not sure about alot of stuff... 1963 75hp Johnson

OMC specified the use of a special tool for centering the orifice plugs in the carburetor throats after a rebuild. I have one of these tools from my many years with a 1962 Johnson 75HP. Will dig around in my parts bin and see if I can come up with a P/N for you. FYI, it's going to use a lot of gas even when it is perfectly tuned! Good luck.

willyclay knows this but he used the wrong term. He meant to center the venturi over the throat. Yey, willy, you want to loan me that tool long enough for me to make some drawings so I can reproduce them?

 

[F_R]

Re: Not sure about alot of stuff... 1963 75hp Johnson

Quote: "Thanks Mister.
So I figured the water choke thing wasn't too big a deal although it would be nice to not have to pull the motor cover off to choke the motor. At least you knew what I was talking about!"

Um...you don't have a little door on the front of the hood to get at the choke lever???

 

[Willyclay]

Re: Not sure about alot of stuff... 1963 75hp Johnson

Frank, you confused me with that discourse about orifice plugs. Never-the-less, the tool is necessary to get it correct which is why I invested in one many years ago. Yes, you can borrow it. PM me an offer!

 

[Willyclay]

Re: Not sure about alot of stuff... 1963 75hp Johnson

The part number for the special tool is 379242. My non-factory manual says: High speed nozzles must be accurately centered in carburetor body. If you would like a free copy of a manual that covers your motor, let me know. Good luck!