1991 50HP Force "jerking"

[wannabefisherman]

Guys, I have a problem that I think may be compounded by another problem. When I run my boat in low throttle everything is fine. When I open it about half to wide open, it starts kicking in intervals of about every 5 seconds. Here are my thoughts: I have a problem with my trim leaking down and I was wondering if maybe this has something to do with the kicking.<br />Also, I've read several posts about "spinning the hub" on force outboards. Can someone please explain to me exactly what this means and whether it is likely to be my problem? Thanks.

 

[dave in toledo]

Re: 1991 50HP Force "jerking"

when this happened on my force(feels like your hitting a log) it was the dog clutch (is that what they call it..) part ;in the lower unit.....

 

[eurolarva]

Re: 1991 50HP Force "jerking"

a spun prop is when the inside hub of the prop is no longer firmly attached to the outside. The inside is a rubber core that looses its bond with the prop. What happens then is the inner hub spins faster then the prop which will cause the jerking you are mentioning. A test for this is to use finger nail polish on the propeller nut and the prop. The propeller nut should have a cotter pin in it. Make the mark on the same place on the prop and on the prop nut. Drive boat and after the jerking happens check the finger nail polish to see if they still line up. If not you have a spun prop and you will either have to get it fixed or replace it.<br /><br /> It could also be your clutch dog in your lower unit or the forward gear. These could be worn down which is causing the clutch to slip from the forward gear. It could also be fuel related. Are you using old gas from last year? Your carbs may be partially blocked so you are not geting consistent fuel and your motor is surging. Does this happen in reverse?

 

[wannabefisherman]

Re: 1991 50HP Force "jerking"

Thanx Eurolarva,<br /><br />No, it doesn't happen in reverse, only in forward. I haven't checked the carbs but that would be the next logical step. By the way, where is the clutch dog located?

 

[eurolarva]

Re: 1991 50HP Force "jerking"

It is inside the lower unit. The clutch dog moves between the forward and reverse gear when you shift. The face on these become worn and eventually you cant get it to stay in gear. I think what you are decribing is fuel related. If it was the clutch dog I would guess it would jump out of gear and not go back. I would buy a rebuild kit for your carb and your fuel pump. NAPA sells both kits for your motor and I am guessing the total cost for both is around 25 bucks. Change out all your fuel lines and clamps as well. The carb rebuild kit comes with really good instructions on how to rebuild and the fuel pump kit is super easy to install. I did these things to my 36 year old chrysler and mine purs like a kitten and goes without hesitation when I goose the throttle. The gas stuff is the cheapest thing you can do to the motor.

 

[dave in toledo]

Re: 1991 50HP Force "jerking"

when my clutch dog went out, i could put it back into forward and go slow into port, if i got going more then a slow idol, it would slip out again, feels like hitting a log.....

 

[wannabefisherman]

Re: 1991 50HP Force "jerking"

Carburetor doesn't appear to be the problem. Does anyone know how to replace the clutch dog? I've never even heard of a "clutch dog" so I'm in the dark on this one (I don't recall seeing that breed at the last AKC dog show).

 

[wannabefisherman]

Re: 1991 50HP Force "jerking"

Thanx Eurolarva, I'll check out the carb option and see what happens.

 

[12Footer]

Re: 1991 50HP Force "jerking"

WBF, does this "jerking", act like a hickup or sneeze? If so, it may be a mis firing condition.

 

[wannabefisherman]

Re: 1991 50HP Force "jerking"

12 Footer - It feels like a hickup about every 5 seconds. If you look at the outboard, you can visibily see it jerk about every five seconds and it almost sounds as if I've hit something in the water. Is it possible that the fuel is too rich/lean? I use the standard 2cycle ratio that is listed on the supertech that I buy but it may be a different ratio for this motor.

 

[dave in toledo]

Re: 1991 50HP Force "jerking"

feels like hitting a log??????

 

[wannabefisherman]

Re: 1991 50HP Force "jerking"

Dave in Toledo - its like hitting a small log. It isn't a huge thud but it does kick noticeably and although I know very little about outboards, I'm sure that this isn't healthy...

 

[eurolarva]

Re: 1991 50HP Force "jerking"

to replace the clutch dog you will have to disassemble the lower unit. To do this you will need a manual and a new seal kit. If you take this apart you will need the manual so you will know how you put it back together again and also the order in which to take it apart. If you dont have a manual a lot of the bigger public libraries might have one. My experience with a clutch or forward gear going bad is it will drop out of gear into neutral. I still think what you are describing is a fuel issue. For 25 bucks you can rebuild the carb and the fuel pump. A lower unit seal kit is around 20 bucks. If the clutch is shot your forward gear is shot and you will either have to have it machined or replaced. New you are looking at probably 300 bucks for parts.

 

[eurolarva]

Re: 1991 50HP Force "jerking"

here is a picture of your lower unit (also refered to as gear case) Lower unit There are about four different models so this may not be your exact motor. Item 24 is the clutch which is your clutch dog.

 

[wannabefisherman]

Re: 1991 50HP Force "jerking"

Eurolarva, this is an awesome diagram thanx! I think I will try the carburetor kit first though, it certainly couldn't hurt since its relatively inexpensive. I'm assuming that Napa carries the kit and I just have to give them the serial from the carburetor?

 

[eurolarva]

Re: 1991 50HP Force "jerking"

These are the NAPA part numbers 18-7037 is the carb kit. I spent 14.88 last spring for this kit. Also get the 18-7806 fuel pump kit. I paid 8.69 fro this. For the fuel pump only replace the diaphram and the gasket for now. I would not mess with the tiny washere that come with this kit. The carb kit comes with good illustrations and will rebuild three different types of carburators. Find the picture on the instructions that looks like your carb and rebuild it. After you remove the rubber seals and gaskets drench it real good in carb cleaner. Let this soak for awhile and then use a thin wire to try and get into small openings to make sure things arent clogged. Use compressed air ( try and keep this below 30psi) to blow everything out and then assemble with new rubber. Sounds complicated but it is all easy. If you have any problems when you have it apart give us a holler and someone will help you.<br /><br />If you did not winterize this motor by removing the gas and fogging it the old gas could have gummed and caused the problems you are experiencing. It could also be what 12 footer is saying by something electrical misfiring. The gas fix is the cheapest and easiest fix to do.

 

[wannabefisherman]

Re: 1991 50HP Force "jerking"

Thanks Eurolarva, you've been a great help. I'll buy the kit and give it a shot. Half the fun of boating is getting your hands a little dirty from time to time. This is a great forum!

 

[12Footer]

Re: 1991 50HP Force "jerking"

WBF,<br />I'm sorry for all the questions, but i still don't know what your motor is doing. But it sounds like it is backfiring,or missfiring.<br /> <br />Check the plugs. Are they bl;ack or "tarry"? Are they wet? Are they brown, or very "new-looking"?<br /><br />Can you get it to quit doing this by choking it partially? (you may have to lock the choke slide partially closed to see). but if this cures the hickups, it may be a lean-burning conmdition. You can also just give the carb's idle mixture screw one-eigth turn counterclockwise to richen it a bit. If this cures it, you just fixed the problem.<br />It could be a sticky reed (decarb cleaner should free it up), or a fouling plug.

 

[wannabefisherman]

Re: 1991 50HP Force "jerking"

12 Footer - I pulled the plugs and they are pretty dark and tarry. The carb adjustment did not fix the problem but I will run a carb cleaner through to see if that helps. How can I tell if I have a fouled plug?

 

[eurolarva]

Re: 1991 50HP Force "jerking"

First off both plugs dirty is a good thing. That means both cylinders are firing and you arent getting water in the cylinders. You should find out what plugs you should be using. The plugs you have may be the wrong ones and they may be fouled. Plugs are cheap and are best to just replace. What kind of plugs do you have in there now? Hopefully someone here knows what kind you are suppose to have for the force. If it was a chrysler I could help. <br /><br />Did you go the winter without running this motor? If so did you drain the gas or has it been in the motor all winter? How old is the gas in your gas can?