1988 85hp force performance

i have a 85hp force on a 88 bayliner 16ft capri br with 2 people on board I'm only getting about 27 mph , this is on a gps . I'm pretty sure it should go faster than this. it has a stock prop and carbs were rebuilt this summer compression was about 120 on three cylinders. it also seems to idle a liitle high and stall when putting it into gear or if i run anround in gear at slow speed for awhile. any help would be greatly appreciated.

Re: 1988 85hp force performance

First, do a compression test on the motor. Ideally all cylinders should be north of 100-110psi and within 10% of one another. If you have low compression in one or all cylinders you will be way down on horsepower.
Second, is your hull sound? If your boat has taken on and absorbed water into the flotation foam over the years you are going to be overweight and that can have a big impact on your performance and your speed. One way to check it is to take your boat to the local weigh scales and see what it reads.
You should be seeing speed in the neighbourhood of 35mph...or maybe a little more with that boat and prop (15 pitch??).
You have some simple checks and diagnostics to do.
Good Luck
BP

Re: 1988 85hp force performance

It sounds to me you may have fouling plugs too....what mixture are you running your fuel at ? You should be running 50:1 . Low speed stalling can often be caused by fouled plugs...throw a new properly gapped set in ,...won't hurt a thing.....good luck bro !

Re: 1988 85hp force performance

shouldn't be any water in the foam as i just ripped out all of the foam and wood and replaced with new. ratio has been 50:1 . and compression was 120 on all three. i will try some new plugs and run some carbonfree through it and see if it helps. i figured it should be going about 35+ as it doent have half the wood a stock boat has, i.e no back to back seats , no seats at the transom , i built it as fishing boat so no need for any of that stuff.

Re: 1988 85hp force performance

1. Any idea how many RPMs the motor is turning at WOT?

2. What condition is the prop in?

3. Is the boat level on plane?

Re: 1988 85hp force performance

unfortunately i don't have a tach on the boat, prop is scuffed on the tips but not to bad, and this is trimmed up. i'll pull the plugs and see what they look like tomorrow

Re: 1988 85hp force performance

I had a similar issue where I wasn't able to go above 4400 rpm at wide open throttle and getting about 29mph (same motor on a 17' maxum with all the stuff still in it). Turned out the problem was the timing and carb adjustments where not set properly - need to make sure the throttle plates open all the way horizontal and no more. Last time out I was getting 36mph at 4900 rpm. I would suggest you install a tach as this motor should be operated in the 4500 to 5500 rpm range a WOT. The tiny tach works very good and is easy to install.
Good Luck

Re: 1988 85hp force performance

do as further suggested and check the throttle opening[especially after having the carbs worked on] and it wouldn't hurt to do a link and sync on the motor to address the idle issue,this will check the timing and throttle adjustment both at the same time. MOPARMAN ROLL TIDE 9-0