need help wich carb change for my force

[bemer]

Hi every one I am trying to find out if i can take my carbs off my old 1990, 90 hp force and use them on the 1985, 85hp force that I have now. Will it give me any more speed ? Will it turn my 1985 from 85hp into 90 hp? I really would like to know and if so, is thier other things I have to do also along with it?


Thank you for your help

 

[jerryjerry05]

Re: need help wich carb change for my force

It probably would work.Even if the #s on the carb are different they will probably work but no more horses.The 85 was rated wrong it was actually a 90.Some mess up in R+D. Something about prop rate and crank rate.Jerry

 

[Frank Acampora]

Re: need help wich carb change for my force

If for some reason you need new carbs on your 1985 85 HP, the carbs from the 1990 90 HP will work just fine. No changes are necessary other than to re-synchronize and set the low speed needles.

They will turn your 85 HP engine into a rip-roaring, fire-breathing monster of----85 horsepower.

So: If you do not need to change the carbs, don't bother.

One of the differences between the engines is that your 1985 is 3.3125 bore and I think--not certain--the 1990 is 3.375 bore. 90 HP has a higher compression ratio also. Again, I am not absolutely certain, but I believe the 90 developed its rated horsepower at a higher RPM than the 85. So in order to take advantage of the carb change, you would need to make at least several other changes to the 85.

 

[bemer]

Re: need help wich carb change for my force

ok thank you for the info. I was wandering how to get the most out of the 85,1985. I have almost everything off of my 90 1990 hp force, what else might I have to change. My 85 runs real good for being a force but when I had my 90 on my bayliner I could get between 40 and 45 mph out of it. wiht my 85 i'm getting about 25 to 30. I have taken it to a marina over here and made sure it runs real good. but I do know that if thiers a way to get more out of it without ruining the engine I would like to find it. and Thank you again for the help.

 

[jim_b_20653]

Re: need help wich carb change for my force

Do you have a Tach on your boat? Are the RPM's the same at WOT with both engines? I believe that the lower unit gear ratio's may not be the same, which means the prop is not turning the same RPM's. You may need a different prop.

 

[bemer]

Re: need help wich carb change for my force

ok so if i put the 90's carbs on it I should put the 90's prop on as well ?

 

[jerryjerry05]

Re: need help wich carb change for my force

Compare pitch on both props.It should be stamped somewhere on the props.
Then run each and see how the prerformance is.
5500RPM should be max at WOT.Jerry

 

[Frank Acampora]

Re: need help wich carb change for my force

The 90 is a much better performing engine than the 85--no two ways about it. But, a 10-15 mile decrease on the same boat is not to be expected--maybe 1/2 that would be acceptable. So while the engine may be running well, it is probably not running optimally. The first thing I would do is to run a compression test. New would have been approx 145-155 PSI while the 90 would have been 155-165.

The 90 definitely has a 2 to 1 lower unit. The 85 will have either have an (approx) 1.73 to 1 or a 2 to 1 lower.To check, mark one prop blade and turn the flywheel by hand with the engine in gear. if the flywheel turns 2 times for 1 prop turn, it is 2 to 1. If it turns 1 3/4 or so, then it is the 1.73. (15 tooth pinion, 26 tooth gears)

If it is the 1.73, swapping the 2 to 1 90 lower unit onto the 85 will give an increase in performance. If you are using the 90 prop on the 85 and the 85 has the 1.73 gears, then it is most likely overpropped. I am guessing that the 90 has a prop with 2 inches pitch more than the 85. If the pitch of the two props is the same, then it could be that the 85 is overpropped right now

The 85 has 5 petal reeds on each side of the VEE block and I suspect the 90 has 4 petal reeds with rubber coated VEE blocks. (I have not yet taken apart my 90 to see) If it does, using the reeds from the 90 will gain a bit of performance because they are about .001 thinner and more responsive. BUT---the four petal reeds have a different retaining screw pattern and will not fit in the 85 reed openings without grinding away a bit of aluminum where the reed retaining screws are.

Well, there's a couple of hints for you. Good luck.