1998 Force 40 surge problem

[Cwr]

I have a 1998 Force 40 that all of a sudden when I get to full throttle it wants to surge about 200 rpm up and down. I took it to the shop and they cleaned the carb and replaced a needle seat, and also put some new style of diapham in the fuel pump. They said they had it fixed but they were sadly mistaken. To top it off this motor is under warranty and they said mercury doesn't warranty carb repair. I have changed the plugs, checked the tank vent, checked the hoses and can't seem to find the problem. I really would rather fix it myself then get charged again for something "not covered under warranty". Does anyone have any suggestions on what the problem may be?

 

[rogerwa]

Re: 1998 Force 40 surge problem

Could it be a slipping prop hub??

 

[Cwr]

Re: 1998 Force 40 surge problem

When I first felt the surge I thought maybe it was the prop, I had wanted to change the pitch anyway so I purchased a new prop at the same time it was in the shop. Made no difference.

 

[Cwr]

Re: 1998 Force 40 surge problem

Is there any way that it could be a faulty rev-limiter? Does anyone have any experience with this particular gadget, if I remember correctly there was a recall on my 1996 force outboard on a rev limiter. If so is there any way to by-pass it to check and see if it could be the culprit?

 

[norman158]

Re: 1998 Force 40 surge problem

how high is it reving?

 

[Cwr]

Re: 1998 Force 40 surge problem

I don't see anything in the book about a rev-limiter, but the guy at the shop said it had one, and I cant find it so it must not have one. But to answer your question it is reving about 5000 and surging in and out. I am going to try to eliminate the antisiphon valve coming out of the tank to see if that may be a problem.

 

[rogerwa]

Re: 1998 Force 40 surge problem

Does pumping the bulb help??

 

[Cwr]

Re: 1998 Force 40 surge problem

Pumping the bulb doesn't seem to help it stays tight. However I noticed last night that the bulb was not tight and that the filter was not full of gas only about 1/4 full. I was about to remove the antisiphon valve from the tank when I decided to wait. I have a six gallon removeable tank in the shed I think I will fill it up and see if it will run any different, kinda to eliminate my fuel system as a problem.

 

[rogerwa]

Re: 1998 Force 40 surge problem

Also, check at every connection for air leaks. With the condition you describe, it would not be a very big one.. I had trouble with the Force quick connect fitting leaking, not getting a good seal.

 

[Cwr]

Re: 1998 Force 40 surge problem

Thanks for all the suggestions, I may need to change out the whole hose assembly. Hopefully the 6 gallon tank will confirm this and I can quit having to worry about it so much. I'm the type that can't get it off my mind until its fixed.

 

[Rex]

Re: 1998 Force 40 surge problem

WHAT DOES THE MAX RPM SAY?<br />REX

 

[Cwr]

Re: 1998 Force 40 surge problem

It bounces between 4700 & 5000, I am supposed to have it proped out to run 5200 rpm, but can only reach that rpm if I hit the choke for a brief second, then it goes back to about 4900 and surges lightly in and out almost like a slight miss.

 

[Rex]

Re: 1998 Force 40 surge problem

YOU GOT PROBLEM WITH GET AIR IN THE FUEL <br />SYSTEM AND THAT WHAT GET TO MAKE THE ENGINE<br />DO WHAT IT DOES.<br />JUST START AT THE BEGINNING WITH ALL THE FUEL<br />SYSTEM.<br />I THINK YOU LIKE IT WHEN YOU FIND IT.<br />SHE RUN LIKE A TOP.<br />I WOULD BET MOST OF THE OTHER MEMBERS WELL<br />AGREE WITH THIS.<br /> GOOD LUCK REX A. HUBBLE

 

[Cwr]

Re: 1998 Force 40 surge problem

Took last night and changed out all the fuel lines inside the cawl of the motor. Some had really bad looking rub spots so I put in a heavier duty line that the original. I wanted to run it this morning and see how it was but it's raining something fierce here on the Gulf Coast of Mississippi. I'll let you guys know hopefully tonight if it works.

 

[rogerwa]

Re: 1998 Force 40 surge problem

If you have an air leak it will be before the fuel pump. After the pump it will be a fuel leak.. So you want to focus the attention on the tank to fuel pump segments unless you can spot leaking fuel..

 

[Cwr]

Re: 1998 Force 40 surge problem

Yeah I should have thought about that, and I think that the line coming into the motor from the connector to the fuel pump had a crack in it. However, I still haven't been able to run it because of the weather, but today is supposed to be all clear. During my lunch break I'm going to take it to the lake and see what she does. Thanks

 

[Liam]

Re: 1998 Force 40 surge problem

An old trick my mechanic uses is to spray carb cleaner around the hoses. When the revs pick up, that's where the leak is (adds fuel instead of air)<br /><br />Good Luck

 

[Cwr]

Re: 1998 Force 40 surge problem

Alright guys I have had no luck, I changed out everything you can that has to do with fuel delivery. I pulled the plugs and according to the manual they are:<br />Cold Fouled - Wet oil or fuel deposits are caused by drowning the plug with raw fuel mix during cranking, overrich carburetion or an improper fuel il ratio. Weak ignition will also contribute to this condition. I have exactly mixed fuel, I have new NGK spark plugs the mixture has been set in accordance with the book, the carburetor has been gone through by a certified mechanic who I knows has high creditials. Should I screw in the mixture screw and try to lean it out a little more or is it time to take it to the shop and have all the electrical components checked out. I am to my witts end, I have always been mechanically inclined but this takes the cake.

 

[Cwr]

Re: 1998 Force 40 surge problem

I think I have it figured out guys, I have a exhaust leak inside the cawl of the motor that is right under the carb. I ran the motor without the cawl on yesterday and it ran like a scalded dog,(for a 40) put the cawl back on and it just bogs. I have my fingers crossed on this one.

 

[Cwr]

Re: 1998 Force 40 surge problem

Okay after a 3 month stay at the boat shop where they changed out all the exhaust system to fix the exhaust leaking into the cawl, the carb has been rebuilt, the fuel pump has been rebuilt twice, I changed out the hose to the motor, bulb primer, quick connector, all hoses inside the cawl, plugs, all compression checks out good. I have tried to hook a remote tank up too, and still the motor will not run as smooth as it once did. I also changed out the prop. When I hit WOT it surges in and out just enough to agrivate me. You can tell something is not right but I have no clue what is the problem neither does the mechanics, can anyone shed some light on my dreary situation?