Force 85 hp runs great first 10 minutes then, only ran half speed then?

[Nomad98]

Hi, I am new to the forum and also new to boat engines and repair. I got a boat with a Force 85 hp for almost free and put new spark plugs into it changed the oil and did some general clean up. Took it out for the first time and it ran great the first ten minutes. Then I slowed down and we were going to change drivers, the engine stalled... It started up right away but would never get up to speed or plane out. The engine ran smoothly throughout but just couldn't get up to speed after the first initial run and would periodically stall, then start right up. I have read a number of forum posts online and decided to install a new fuel pump diaphragm (just ordered but not installed). I also checked to see if the gas tank vent was clogged and it isn't (was reading a lot about fuel delivery issues). My neighbor is a mechanically knowledgable and is helping me with the engine. He the said he thinks it's maybe points and condenser or coil pack. I am wondering if anyone on the forum can give me some insight into this or a similar condition before I purchase a bunch of parts. The engine is a Force 85 hp 1987 serial #856X7A Thanks in advance for any suggestions or comments.

 

[Nomad98]

Sorry for the double post. Got a database error so I posted again thinking the first post didn't work...

 

[NYBo]

Welcome to iboats! :welcome:

There are no points or condenser in these motors; they have magneto ignition systems.

Start with the basics: check compression, check all three cylinders for spark. And change that fuel pump diaphragm. Then read the stickies at the top of this forum area on how to synchronize the carbs and set the timing if everything else checks out.

 

[Nomad98]

Thanks will do, I was searching for points and condenser and could find nothing... That's why!

 

[Jiggz]

First, go to W-mart and buy the G2 clear fuel filter (less than $5) and install it between the fuel pump outlet and the carbs inlet. Hose clamps already come with the filter so all you need to do is cut the fuel hose and install the fuel filter. Now try running the motor again making sure you prime it well with the primer bulb and with the clear fuel filter full. If the fuel filter stays full and the engine would not achieve speed, then you either have a carburetor problem or electrical problem. If the clear fuel filter empties, then you have fuel delivery problem from the fuel pump, leaky hose, leaky primer bulb, or clogged or restricted pick up tube or tank vent.

Second, buy an inline spark tester from any auto parts store (less than $10) and test for sparks in each cylinder. There should be consistency in the sparks and not misfiring.

Post your results and we can troubleshoot from there.

 

[Nomad98]

Great suggestion. I got the fuel filter last night and installed it, the filter was consistently full once the engine was running (idled or with the throttle up).

The engine ran smoothly at first then started to misfire. When I changed the spark plugs (a few weeks ago after I got the boat) one of the plugs had the spark plug boot coil corroded so badly that it stayed on the spark plug when the boot was taken off. I tried to clean off the coil and put it back together but I am thinking that this may be the problem. I ordered a new one and this weekend or the beginning of next, I am hoping to put that in.

I will try to get an inline spark tester today... Thanks for the help

 

[Jiggz]

Well, hopefully it is just the ignition coil that is causing the misfiring and fix your problem. Keep us posted.

 

[Nomad98]

Got the coil yesterday and put it in... No backfiring and it seems to run the way it was meant to. Will test it on the water this week.

 

[Nomad98]

Put the coil in and a new diaphragm for the fuel pump. It still only maxes out at 2500 rpms in the water. Also it will stall, then start up right away, plus the engine will have these little rev-ups like it's gonna kick in but then it doesn't (the rev-up is barely a second). When I check the inline fuel filter it still has fuel in it.

 

[Jiggz]

I wish you had posted if the fuel filter was full, 3/4 full or 1/2 full or less instead of vaguely describing it still has fuel in it. So I'll assume it at least has 3/4 full. This means the problem is with the carburetors or it could also be with the timing and advancing of the trigger. So we will have to eliminate the carbs first. Dismount the carb bowls one at a time and then check and clean the floats, needles and inlet ports. If you dismount the entire carb, you can simulate fuel flow by slowly blowing (I use a short fuel hose to make it easier) into the carb inlet nipple or tube, and raising the float with your other hand. With the float in horizontal it should stop you from blowing into. However, if it stops you even before it goes horizontal, you need to reset the float. Or worse yet, if it won't let you blow into it with the float in full down position, indicating you either have a stuck needle or clogged inlet port.

You can do this on all three carbs or if you want you can do the spray bottle test first to identify which carb is causing the problem. To do this, run the boat in the water with the cowl off. This requires a two man operation. When you start to open up the throttle and the motor is bogging down, spray fuel oil mix directly into each carb (you will have to remove the carb cover to do this). The carb that makes the engine rev up is the on you want clean and inspect. While those carbs that worsens the case or bogs down the motor more are actually working. They make the motor bog down more because of too rich of fuel mix since they are already working properly. While the one that makes the motor rev up some more when sprayed with fuel mix is not working properly hence when sprayed it will actually cause combustion and increase rpm.

 

[Nomad98]

Sorry for being vague... fuel filter is full.

Do I just put fuel/oil mix into a regular spray bottle to do this or is there a special bottle I need to get (thanks for your patients)?

 

[Jiggz]

A regular clean spray bottle will do. You can also just re-use an emtpy glass cleaner spray bottle or go to a dollar store and buy one of their spray bottles. All that is required is that is works and very clean. Just make sure after you get done with it, pour the remaining fuel oil mix into your tank and not let it sit in the bottle. Some plastic bottles cannot handle gasoline and melts.

We've had two similar problems like yours before. One was resolved with an improperly set carb float. The other one was a little more unique in that one cylinder does not fire up despite having good compression, spark and fuel in the cylinder. The cause, the carb's throttle was loose and is always wide open thus flooding the carb and cylinder constantly!

 

[Nomad98]

Jiggz, great suggestion with the spray bottle... worked like a charm! Took the boat out and we found two carbs that bogged down, and one that did nothing. Put in a different coil pack on the dead carb, dropped the boat in the water and off we went! Really seems like a dream to have it running, Thanks!

 

[Jiggz]

You're welcome and thank you for coming back to post the happy conclusion or resolution to your problem. It is completed thread like this that are very helpful for other members by simply relating their problems and symptoms. Cheers and enjoy!

 

[Nomad98]

Well, the dream is over. Took the boat out again last night and sure enough after about a ten minute run, the engine starts to bog and then it almost dies. I bring the throttle down and then throttle it back up and it was running like before when only two cylinders were working. Didn't have a spray bottle to verify that but by the way it ran I would bet on it.

So here is the setup. I have a new coil on the third plug and two old on the first and second plugs. The first plug was the dead one that we found last weekend. I had an extra old coil that I put on the first dead plug and that seemed to fix the problem on Sunday. Sunday it ran about a half hour on three cylinders, then last night it ran about ten minutes and then, back to two cylinders.

Do I spring for two new coil packs so all three are new, or do I start to look some where else? Remember, when the spray test was done the first cylinder was dead, wouldn't bog or speed up when fuel was sprayed into it.

 

[Jiggz]

Troubleshoot again. Don't presume until you are 100% sure a part is faulty. Do the spray bottle test again and switch coils to see if the problem follows. Then you know for sure it is the coil. Replace bad parts especially electrical components with new parts whenever possible.

 

[MickLovin]

Have you tried putting the new coil pack on #1 to see if it fires #1 cylinder?

 

[Nomad98]

Well, I swapped coils and the problem followed the old coil pack. Today two new coil packs are arriving. Once I put them in all three will be new and that should do the trick! (Fingers crossed, knock on wood!) I will post results.

 

[Jiggz]

If the problem follows, no doubt the coil is bad. Hopefully, with all new coils your dilemma will soon be over. Goodluck.

 

[Nomad98]

Well, just to close things up... The problem followed the bad coil so I bought two new coils. All three are new and I have been running the boat all week without any more "low power" issues. Thanks for all the great advice!