Force 85hp low top speed

[Winstoper]

I am new to this forum and I hope to get some answers, I have a 1984 bayliner trophy bass boat (that I just bought) with a 85 hp force motor, seems to me that the top speed is pretty low, I have checked spark, compression, timing and fuel and all seem to be working as they should. The top speed according to the boat is 25 and 31 on my gps. 31 seems a bit low. The rpm on the boat gauge says it's only getting to 3500. (Which is way low I think) The carbs are opening up all the way. The prop is a Chrysler stainless steel part # a511265. Does anybody have any suggestion? 31 seems way low and it's just me in the boat.

 

[pnwboat]

Re: Force 85hp low top speed

According to what I see out on the internet, that propeller is a 21 pitch. Too much pitch for that 85HP motor. Typically a 19 or 17 pitch prop would be the most you would want to use. You should see around 5000-5500 RPMs at WOT with the correct prop.

 

[Frank Acampora]

Re: Force 85hp low top speed

With a 21 pitch prop, you are lugging the engine and yes, top speed will suffer. However don't expect miracles with a prop change: You MIGHT get high 30s but I think 40 would be out of the question.

And please post your location. Some one near you may have a decent prop and be willing to trade--but, of course, offer a trade in a private message to comply with forum rules.

 

[Winstoper]

Re: Force 85hp low top speed

I Agree with the 21 prop I was hoping to get a little reassurance from somebody before I went and spent the money on a new one. Thanks guys

 

[jerryjerry05]

Re: Force 85hp low top speed

You have the 16ft? I rigged a lot of these.
It will go over 40 if it's set up right.
You have the power tilt?It will help with top end.
Not having it will slow you down some but still push at 40
Pics of the boat? Too much load?
Look around you can find a prop to test so you don't waste a lot of $
Make sure the linkage is advancing all the way too.
The plastic connectors could be cracked and not working right.
Make sure the trigger is advancing all the way too.

 

[MickLovin]

Re: Force 85hp low top speed

Ok I just read this post and Winstoper has the same prop as I had on my 75hp A511265 Chrysler which ran my chrysler 75hp fine but I didnt expect more than 40MPH, at 5000rpm+, I have a 17ft carribean and the next photo is my 100hp but I dont have a prop photo

 

[Frank Acampora]

Re: Force 85hp low top speed

Before you go buying a new prop, look on ebay under Force/Chrysler propellers. There are a couple of decent ones there for about half the price of a new one. Don't be worried: Your circa 1984 Force can use Force props OR late (1980 or later) Chrysler props. Closed hub or thru-hub exhaust makes no difference in performance.

 

[jkust]

Re: Force 85hp low top speed

We've got an 85 HP on an 84 Bayliner but it is the 16 foot capri and weighs #1005 lbs dry so ultra light build. We run 17 and 19" props and get low 40's loaded up and get there instantly. No tachometer so no clue where the rpm's are. Many years ago we bought a dozen props at a marina going under but the lake the boat resides on is so deep, the props have never touched ground so never needed to use all the extras.

 

[Winstoper]

Re: Force 85hp low top speed

I don't have any pics of the boat, but it is a 17ft trophy bass boat, visually it looks like advance is opening all the way. I really am leaning toward the prop. If I find a good deal on one I will try it out and post back my results. Thanks guys

 

[Winstoper]

Re: Force 85hp low top speed

Well got the 17 pitch prop put on and took it to the lake today, I am getting 41 mph. Just what I was looking for. Thanks for the help.

 

[pnwboat]

Re: Force 85hp low top speed

Glad it worked out for you and thanks for the update.

 

[SkiDad]

Re: Force 85hp low top speed

awesome

 

[MickLovin]

Re: Force 85hp low top speed

I am surprised that yo have gained 10 MPH for changing to a 17 from a 21, wonder if it is worth me trying a 17.