force 90 dies under load

[dabutcher]

Engine runs good in neutral and revs well.Then when i take it out on lake and try to make it fly it will only go at low speeds and dies when I floor it to go fast. Does not make any difference if i increase throttle slowly or all at once? thanks for all help. Rookie in the Twin Cities.

 

[eurolarva]

Re: force 90 dies under load

When testing at home are you using muffs or a water tanK? My guess is muffs. Chances are you are not firing on one cylinder. When put in a lake back pressure makes this more obvious. Remove the spark plugs and look at the tips. A clean plug tip will be the bad cylinder. You will need to do a compression test and a spark test to determine if this is an ignition problem or a blown head gasket or worse. I live in brooklyn park so if you want to borrow my compression tester feel free or bring the boat here and I can test it for you.

 

[roscoe]

Re: force 90 dies under load

As was answered in your other post:

Do you know how long it sat since it was last used?
Did you have the drive unit in a tank of water when you ran it?
Or on "water muffs" ?
Or was there no water at all when you started it on the trailer?

Several things come to mind.
1- one of the sparkplugs is not firing
2- one of the cylinders has low compression
3- carburetors are gummed up and running lean
4- fuel pump is going bad
5- vent on gas tank is plugged

At this point, we need to eliminate some of the possibilities.

You need to check to see if all the sparkplugs are firing.
And examine the plugs to see if they all look the same.

Then check the cylinders for compression. Post the compression readings here.

Ask here if you are unsure of how to do any of these things.


You still have to determine if it is a fuel, compression, or spark problem.
Then we can get to work on the solution.


Take eurolarva up on the offer.
Take your boat over to him and let him help you out.
He needs something to do.

 

[dabutcher]

Re: force 90 dies under load

Thank you two gentlemen for all the tips. i will try to do some testing on monday as I need to remove my boat from the Bayliner dealers yard and bring it back home.I have muffs. Would you reccomend a tank instead. Seems easy enough to set up.As far as testing for spark? Do I remove one spark plug and put it in its wire connector and hold it near the block?Should the other two plugs be removed so that engine does not start?I have a compression tester i have never used.i will do compression test also.this gas tank does not seem to have a vent? Any ideas on where to lok for it?Thanks again,Darryl

 

[roscoe]

Re: force 90 dies under load

Remove the other two plugs and ground them to the engine.
Look for 7/16 blue spark on the one you are testing.
You should be able to simply unplug one plug wire at a time while the engine is running, and you should hear a drop in rpm when you pull the wire.
If you don't hear any difference, that plug was not firing.

When you do the compression test, simply flipping the safety lanyard switch will disable the spark.

Yes, a water tank would be better.
These Force lower units don't work well with muffs.
Also, a tank will put back pressure on the engines exhaust, just like having it in the lake.

Do you have a built in tank, or a portable tank?
Portable tank will have a screw vent somewhere on the top.

Built in tank will have a vent hose running out of the tank area to an outlet above deck, usually near the transom.

Keep us posted.

 

[dabutcher]

Re: force 90 dies under load

I DID THE DECARBING OF MY ENGINE. NEXT I TRIED TO DETERMINE IF I HAD SPARK ON ALL THREE CYLINDERS. I WENT TO PULL THE FIRST TOP PLUG OFF WHEN IT WAS RUNNING AND COULD NOT DO IT BECAUSE OF MASSIVE SHOCK! IS THIS NORMAL? ALSO COULD NOT RUN IT IN TANK.ALL MY BARRELS ARE NOT WIDE ENOUGH. WHERE DO YOU BUY A TANK OR IS THER A WAY TO MAKE ONE? I HAVE A WIRE THAT IS NOT CONNECTED TO ANYTHING? IT IS WHITE AND ONE END GOES INTO A RUBBER PLUG IN VALVE COVER OR WHERE THE SPARK PLUGS ARE? I CANNOT FIGURE OUT WHERE THE OTHER END GOES? THANKS,DARRYL

 

[Bry21317]

Re: force 90 dies under load

I will let the other experts tell you more, but from my Experience, when you get shocked the boot is bad.

The boots that come on the engines are not that great to start with. I had a friend who worked at a Motorcycle shop and he got me some NGK Right angle boots, they have been on for about 5 years and work perfect still.

Here is a Link to a picture of them that I found. Go down to where it states NGK Spark Plug Boots, then you will see the picture. It is about 3/4's of the way down the page: http://www.650central.com/ignition.htm

Have you rebuilt the carbs? Mine would die over 2000rpms and it was something in My carbs causing it.

I have an 88 Force 125hp. It ended up being the Needle that is moved up and down by the float to allow gas into the Carbs. The needle was sticking and the bowl was running out of gas. It now runs like a champ once that was found and fixed.

Hope this helps, as I know how much of a pain it is when you can't find the problem.

Thanks,
Bryan

 

[rottenray6402]

Re: force 90 dies under load

At least you know that one cyl has spark if it shocked you! :^ You can pick up a special pair of pliers at an auto supply store that are made for removing wires while running. They have rubber ends that insulate you from the spark and have a unique shape to grip the wire.

 

[roscoe]

Re: force 90 dies under load

Definitely use insulated pliers.

You can run down to Fleet Farm and get a stock (cattle) water tank for about $50. The metal 100 gallon ones work great.

You can back the boat up to it, tilt the motor down, and you are set.