Force 120 Bogging down at high RPM

[DoPage]

Hey guys.....<br />I have a '96 Bayliner Trophy and a 120hp Force by Mercury on the back. I bought the boat in Nov. and have had it out many, many times without a problem...it ran great. Just 2 weekends ago, I was with some friends and we were just trolling slowly for a while when the engine started to miss heavily and when I put it back into Neutral, the motor would rev high and then in about 30 secs. return to normal idle. I changed the plugs, fuel feed lines, and decarbed. The motor starts right up and idles fine, even with a little throttle, but, when I try to give it any real throttle, the engine starts to miss and sputter until I return it to idle. then it's fine. Any suggestions. I also had the carbs cleaned by a mechanic.<br />Thanks for any replies.

 

[eurolarva]

Re: Force 120 Bogging down at high RPM

Hello DoPage and welcome to iboats. Were the carbs cleaned after the symptoms occured or before? After the cleaning did it improve or get worse or stay the same? When you attempt to increase the throttle have you tried choking it when the motor starts to sputter and if so does it improve the motor or make it worse? Sorry for the 20 questions routine but some of this stuff may be helpful in figuring out the problem. Have you ever rebuilt the fuel pump? That is where I would go now. Cost is about 10 dollars and it is pretty simple to do. Remove 6 screws remove a gasket and diaphram, put a new one in and put the 6 screws back in. You will probably need a 18-7806 kit which Iboats sells HERE

 

[DoPage]

Re: Force 120 Bogging down at high RPM

The carbs were cleaned after the symptoms and they ran different but the problem remained the same. I've tried choking with the throttle and the engine will die. I've never rebuilt a fuel pump, but, I might try just about anything now. I have had a suggestion that the Stator may have gone. It has the red stator right now...Do you know the reading I should get on the stator wires? I have an ohm meter and would like to measure that...thanks

 

[eurolarva]

Re: Force 120 Bogging down at high RPM

I am a chrysler guy. Roscoe will have to help you with the stator readings. The good news is the red one is the good stator versus the black one.

 

[roscoe]

Re: Force 120 Bogging down at high RPM

Fuel pump is a good thing to do, probably time to do it anyway.<br /><br />96 was the first year for the CDM ignition.<br />You can check the yellow wires off the stator for ohms, don't have my book here right now, but if you check it and post the numbers, I will get my book back in a day and check it for you.<br /><br />You can also check the charging voltage across the battery terminals.<br /><br />Does it still rev real high at idle, or was that a one time thing?<br /><br />Take a real close look at the linkages between the carbs and the trigger. Here is a picture, pay close attention to parts at the top, # 14 and 15, etc.<br /><br />Look for anything loose. Make sure all the parts are moving when you advance the throttle.<br /><br />

 

[DoPage]

Re: Force 120 Bogging down at high RPM

The motor does not rev high at idle anymore since the carb adjust. I had my mechanic measure accross the stator and readings were way off. I looked up what they were supposed to be. I was wondering where is the best place to buy one. I currently have the red one and it has some kind of adapter "box" connected to the wires (Gr/White and Green). I'm looking for a decent price and do I need to also replace the adapter box between. <br />I hope this doesn't sound too rediculous.<br />Thanks for any help.