View Full Version : 85hp force runs great in smooth water but floods in rough

05-19-2009, 06:40 PM
"I can get my boat to run all day as long as the water is smooth like when im fishing in the coves, but if I hit out in the main lake to travel across it, a few minutes after hitting rough waters or someone elses wake the motor acts like it is flooding out or starved for gas. clean carbs. clean fuel and filter. any ideas."

05-23-2009, 08:35 PM
This is a 1988 Force model# 856A8B. Need some idea's on what problem im having. Anybody have any ideas?}}}

05-24-2009, 01:08 AM
"I have a 1984 Bayliner Trophy bass boat with an 85 horse Force and not long after I bought it, I had the same problem as you are experiencing. I took it to 3 different mechanics and none of them could figure it out. I finally found a guy that specializes in Force engines. He sold me a fuel pump diaphram. 5 or 6 screws and it's replaced. Simple fix and the gasket was about 2 bucks.
Give that a try. If your bottom cylinder is flooding out, I'm betting the fuel pump diaphram is the culprit.
Post your findings. I'd be interested to know if that takes care of it for you.
Good luck....."

05-24-2009, 01:36 PM
"That's interesting to know, thanks for the update. I will check that out, because I have check everything else that i could think of. im just glad somebody had the same problem as me and i was not the only one. thought I was going out of my mind, people told me it was just a coincidence , that it was i just happen to hit rough water at the time it was shutting down on me"

05-27-2009, 08:06 PM
"Ok, i rebuilt the fuel diaphram, primed the bulb, fired it up and had a hard time keeping it at idle. adjusted the throttle, then it idled fine until i rev up the motor a few times, then back to idle and it dies asap. checked the filter again to insure i was not picking up trash, then checked the screen at the pump to make sure there was no trash that i missed between the filter and the pump. nothing found. checked my plugs, found that they needed replacing. replaced them. motor is running better now. I guess the next thing i need to do now is put the boat in the water under a little back pressure and adjust the carburetors a little further. (JUST CANT FIND OUT THE EXACT SETTING FOR THE MIXTURE SCREWS...


05-29-2009, 03:03 PM
"When I had my "problem" with my motor, one of the mechanics had rebuilt the carbs, messed with the idle and timing and told me it was fixed. It still wasn't running on the lower cylinder so when I finally figured out it was the fuel pump diaphram, I had to reset the carbs and adjust the timing.
The carbs are easy to adjust. Start the engine up, turn in the adjusting screw in until the engine starts to run rough or slow down. Then adjust it back out until it runs right. I opened mine up just a little more to make sure it had enough to lubricate everything. 2 stroke engines get thier lubrication from the fuel so I didn't want to hurt anything by lack of lubrication. Your engine has 2 seperate timing adjustments. One is for the timing at idle and the other is for high speed. They are easy to adjust but they must be dialed in seperately. It would be helpful if you got a manual but even without a manual, it's and easy adjustment.
Take the plugs out so you can spin the motor up without it running with the starter and you can adjust things from there. Just make sure that you have the plugs grounded when you make the adjustments because it's possible to fry the ignition if you don't have the plugs grounded and the ignition is not a cheap fix.
There are two marks on the flywheel for the high and low speed timing.
I'm not a mechanic, I just went to the boat store and read the manual from there.
It would be helpful to at least talk to a Force mechanic and ask him if my advice is good or better yet, have him do the work. That way, if something goes wrong, he would have to fix it. Like I say, I'm no mechanic, I'm just telling you what I did to fix mine.
Good luck and let me know how it works out for you. My Force has treated me pretty good. I'm very happy with it so far."

05-30-2009, 05:17 AM
"the top cyl works the fuel pump in my motor. hold the diaphram up to a light and look for any pin holes in it. i have never heard of it causing the problem you discribed, please post back and let us know so we can log that as a fix.
when adjusting the carb. don't screw the needle in tight... you don't want to damage it. back it off i and a half turns, then with the motor warmed up turn the needle in a quarter turn at a time letting the motor run for a few minutes and listen to how it sounds. keep turning in quarter turns, waiting for a minute or two between turns until it starts running rough, then go the other way counting the quarter turns until it runs rough again, then go back half way, the middle of the two points where it started to run rough, that should do it. i would also use some Sea Foam and de-carb the motor. IMPORTANT NOTE just remember scrwing the needle in leans it out and turning it out makes it rich... after you have adjusted your carb and give it a quick test run, check your plugs... you don't want them white or light gray... that is to lean and you could stick it. better a little rich than lean, plugs are cheaper than pistons."

05-30-2009, 05:48 AM
"check my last post, i think it is the top cyl. it has been years since i have messed with the fuel pump.

checking the timing... when you set your timing and you want the thing to run as good as it should, you need to do it at WOT. pulling the plugs and spinning it with the starter is okay to let you know it will run, hut you need to do it with the motor running AND IN WATER, don't do it with muffs... aside from over reving it has to have the back pressure and be under a load. go to the bay or lake which ever, leave your boat on the trailer and leave the back of the boat tied off to the trailer just like when you hauled it down there, then let the motor warm up, after it has warmed up you can put the timing light on it and run it at WOT without a problem. this is the best method i have found, some people will tie off to a dock but on the trailer gives you the best plateform to work from and it is safe, don't try and do this with the boat moving it is to hard to do any kind of a good job with the boat moving. just leave it on the trailer and after you set the timeing just pull up a little and un tie it and put it back in the water and take it for a test run. make sure you know where the timing should be, it isn't always on the timing marks shown at the flywheel. they have changed the timing from the original settings on several models so make sure you know what it should be timed at. just like with the carb adjustment, if you have it to far advanced, it may run a little better but it will also run a little hotter and that is not a good thing"

05-31-2009, 03:13 PM
Sounds like the tiny springs round the float pin are missing. These were fiddly little springs that applied pressure to hold the floats closed in rough water. This stabilizing of the float helped and if missing could cause your problems.

06-02-2009, 02:44 AM
you need to get a manual so you can verify which carb is on your motor. these motors used several different carbs and some of them don't use those springs. but william does have a good point because if your carb uses them and they are missing that might cause it to run like that in rough water... if you didn't take the carb apart before this problem started then they would be laying in the bottom of the float bowl... there is only one other place they could go and i doubt they could fit through the main jet. have fun and good luck. oh.... don't forget to de-carb that motor with Sea Foam... plobably cure your poor running problems. here is a link to tell you how... you may have to copy it and put it in your browser http://www.switchbait.com/forums/showthread.php?t=159

06-02-2009, 06:40 AM
"Ok, i dont remember seeing any springs in the carbs. other than the ones that are on the pin holding the float. and yes i will look and double check in the manual to see which carbs i have, and as far as the sea-foam, its already in the tank.

thanks for the replies gentlemen, i will update when i get further along, right now going to work and trying to get my hands on a timing light, but looks as if i will have to buy one.

catch up to yall later on my newest findings."

06-02-2009, 10:45 AM
"The "ones holding the float" maybe the ones I'm referring to. They have a small tab on each end and have to wind up on the pin in such a way they put just a little force on the float to close it. It's real fiddly. you need to do it as the pin is being put thru the float pivot. If you had done it, you would have remembered. !/2 the time you drop them and 1/2 the time the tab dosn't catch the float right.

Hope this does it- I've been following your dilemma with interest. Just about every thing that can cause this has been mentioned."

06-12-2009, 03:36 PM
"Have not had time to mess with the boat here lately , but i will update when I get the chance to mess with it."

06-19-2009, 03:57 PM
"Put my boat in the water at 7:30 a.m, and by 10:30 a.m it was back on the trailer. this time it had flooded out right when i hit another boats wake. ran great until that point. checked the springs in the floats, and they seem to have a little tension on them. i do remember doing that now that i tore back into it. I have done everything that i know to do to this motor. putting it in the shop in the next couple of weeks. will update and let you know what the cause was, if they find it."

08-17-2009, 10:45 PM
Change the three check valves behind the fuel pump. $5 for each one.

08-17-2009, 11:33 PM
"Those are the "puddle trap" system and they run un-burnt fuel from the bottom of the engine to the top for a re-burn and could very well be your problem- but indicate an in efficiency in the engine some where. Maybe the seal ring between the cylinders, or a bad seal on the crank shaft. You can take that long vertical plate off the engine and blow thru the little valves and see if they work. You might get this problem licked yet!!!"