1997 force by Mercury not working at its best

[mochosla]

Hi,<br /><br />A few months ago I bought a 1997 maxum boat with a 120 HP Force by Mercury of the same year. The first few times I took the boat out it run very well with a top speed of 45 miles per hour. Then it happened, it started to loose power and would take off very sluggish. Then it would work fine. For the last 4 or five times that I have taken the boat out, it does not go any faster than 35 M/H with a sluggish take off.<br /><br />I have done the following:<br /><br />Replaced the spark plugs<br />Use hiest oct gas and best oil in the mix<br />Verified that all pistons are firing<br />Verified that all coils are working (to the best of my knowledge)<br /><br />I'm lost to say the least. I don't know what else to do so any help will be greatly appreciated.<br /><br />Thanks.

 

[WillyBWright]

Re: 1997 force by Mercury not working at its best

First, you're talking about a Force in the Mercury board. You'll probably be moved to the Chrysler/Force board. If you don't see any more answers here, look there.<br /><br />You could have a carb with a clog or a float valve stuck closed. Two carbs...four cylinders. The upper carb feeds the upper cylinders, the lower feeds the lower cylinders. Try running the motor with the upper two sparkplug leads removed. If it runs the same, the problem is probably the upper carb. Try the same with the lower two sparkplug leads removed. It could also be water in one or both of the carbs. Water is heavier than gas, so the lower carb usually gets water in it first.<br /><br />A compression test would be a good idea if you have a gauge. If not, I'd bet a someone you know has one. Otherwise, they're not very expensive. Expect the upper cylinder to read lower than the other three by 10psi or so. Heat rises, so they lowered the compression ratio in that cylinder to run a bit cooler. Otherwise, the readings shouldn't vary from each other by more than 10% or so.

 

[bluebyyou]

Re: 1997 force by Mercury not working at its best

I vote for getting the carbs cleaned out. Are you running out of a metal gas tank? Sometimes rust and other crud can get in the carbs. After doing the carbs I'd add one of those clear inline fuel filters.

 

[mochosla]

Re: 1997 force by Mercury not working at its best

Thank you both for your answers. I have already done the compression test. Three of the piston are @ 140, the last one is @ 135 PSI so the compression is good. <br /><br />A clugged carb sounds like a possibility as the boats sometimes will be running sluggish and it will start functioning fine just out of the blue.<br /><br />I have a built-in plastic gas tank so it should not be rust.<br /><br />I will attempt cleanning the carbs (I hope I don't mess it up even worst as I don't know how to set the jets right. Any input?<br /><br />Tanks again!!

 

[moderator1]

Re: 1997 force by Mercury not working at its best

Moving to Chrysler and Force Questions.