1985 force compression

Whats up guys , i have a 1985 force 125 outboard and my compression readings are no.1 126, no.2 124 , no.3 128 , and no.4 122, is this ok , the motor runs great it pushes my 19 foot bayliner cuddy around 40 mph , thanks guys

Re: 1985 force compression

Looks good to me.

Re: 1985 force compression

This looks like great compression readings to me. Your biggest spread appears to be 6psi...this is nothing. The general rule of them is for all of them to be within 10%-15% of one another and for the lowest to be over 100psi (ideally). You've got all of that covered and then some.
That said, check with Frank A....he will give you specific info on these readings as they pertain to your particular motor.
That said, I think your good to go.

Re: 1985 force compression

Old Chrysler compression ratio for that engine was 145 psi and I doubt Force changed it.

That said, unless you have an expensive professional compression gauge, they all give different readings and your technique may also cause a lower than normal reading--so: your compression figures are good; all within a few pounds of each other, and considering you get 40 mph--which is respectable--If it ain't broke, don't fix it.

You can try playing around with props, engine height on the transom, and trim adjustment; you may be able to squeek out a few more MPH. But you are in the range. Being a little heavier than a 19 foot closed or open bow runabout, a 19 foot cuddy won't get much more with that engine.

Re: 1985 force compression

What do you guys think of a 83 85 FORCE outboard with 85 psi on all three cylinders? The majority of the compression readouts that i have seen usually have 120 psi or more. Is having 85 psi on my outboard acceptable or does it mean that im losing power and a rebuild might be in order. I can get her up to approximately 32 mph on a 16 foot bayliner. This is all the speed that i need considering i mainly tube and fish from it. Thanks guys.

Re: 1985 force compression

Well, Jack! At 85 psi the compression sounds a little low but the real thing to look for is unequal pressure between cylinders--more than 10% difference--that indicates damage. And, your gauge may be reading a little low.

I would expect a little more speed from that engine on a 16 footer--BUT--

You state that you are happy with the speed and apparently the engine is working well for you. So: Why go for an expensive rebuild on an engine that right now satisfies your needs? Don't mess with success!

Have you played around with various props and engine height settings on the transom to get a couple more MPH? Is your prop in good condition? A damaged prop will lose speed.

The incorrect prop, or incorrect trim setting can have a drastic affect on speed. And if you don't have one already, invest in a tachometer--better than guessing where you are. Engine should be propped to run 5000-5500 RPM at full throttle. And if you don't have another prop, an extra is always a good idea. No need to buy a new one--get a good used one off ebay.

all these things are easier and a lot cheaper than a rebuild.

That boat in the avatar is a 15 footer with a Chrysler 90 on it. It goes 42 MPH at 5000 with a 19 pitch prop. I would try your engine on the 16 with a 17 pitch prop--no less-- but 19 might be too much. Pull off the prop nut and washer. The pitch should be stamped into the hub.

Re: 1985 force compression

thank you guys for all your help and knowledge on everything , you guys are great

Re: 1985 force compression

I am pretty sure its proped at 16 and i havent adjusted the trim levels at all. Its a manual trim so its a pain in the but to adjust. I might up the prop and see what that does, im sure more speed would be nice but really not necessary at this point. I greatly appreciate the help but for a first boat I am just trying to learn as much as possible from it. Do you guys think its worth the 500 bucks to put a trim kit on it for ease of use. I really dont mind lifting it up manually when im loading and unloading. But i dont have a tach mounted and i have been debating on installing one. Ill do some research on installation seems like its totally worth the installation. Thanks again

Re: 1985 force compression

Jack, you're on the right track by taking Frank's advice and installing a tach first. Without knowing what you're rpm's are at wot you're taking a shot in the dark and throwing money at a problem that may not even exist!

Re: 1985 force compression

I would be re-checking that compression reading JackD. My 85 horse on my 16 footer had low compression and the boat would max out between 32 and 35 depending on what and who I had in the boat. I rebuilt the engine from top to bottom, went through the entire fuel system including the fuel recirculation system, actually retarded the full timing to 28 degrees, and did some other upgrades over the stock setup. I removed the two metal fuel cans that sit under the transom in the back and mounted a below deck 19 gallon fuel tank and installed a filler and vent which added a fair amount of weight to the stern when the tank is full. With all this done, the boat hauls complete arse, gets up on a plane effortlessly, and taps out at 38 mph no matter who or what I have put in the boat yet. Of course I haven't put 6 people in there with all there crap but it use to get 32 at best with me, my wife, and my 8 year old son in it.

Re: 1985 force compression

I appreciate the advice, however i dont think i am going to do a complete rebuild at this time. But i am going to take it to my motor guy and have him replace the water pump impeller, clean the carb maybe do a rebuild, and give it a good once over. With all this done, my plan is to run it to the ground and wait till she blows. But I will definately not neglect her, shes just my starter boat and i dont mind putting 600 bucks in for some general maintence but a compete rebuild at this time can wait. My hope for this boat is to last me about two or three years so i can get used to the life and the general requirements of boat ownership and then purchasing brand new. I only paid 2k for the boat from a friend and shes in mint condition so i think i can squeak out the time frame i am looking for. But i will say if she dies and needs rebuild i have no qualms about dropping 1500 bucks for my guy to do a rebuild. With the condition the boat is in that would put the total price at 3500 and in my opinion i would still be ahead. Ill post some pics sometime so you guys can see what good condition she is in, its amazing to have an original boat thats 20 plus years old that looks almost new. Thanks again for the help guys.

Re: 1985 force compression

Why sink in 600 bucks when you can do the work yourself with only regular hand tools? It's easy unless you are missing all your fingers. An impeller is only about 17 bucks and lower unit gear oil is about 5 bucks. A little WD 40 cleans out carbs nicely as will Seafoam for another couple of bucks. Plugs are about 5 bucks each at the marine store, 3 at the auto store. And figure 30 bucks for a Clymers manual. The money you save can go toward a power tilt/trim.

500 seems about right for a new trim/tilt but I think you could do better. Send a private message to RRitt. he does a lot of trim/tilt units. Or, keep looking on ebay. It's easy to install: a switch, a couple of relays, one bar at the bottom of the engine clamps and one bar at the top inside the swivel assembly. Should take about an hour to install a complete unit. Believe me! Once you go to power trim, you will never want to do without it.

Re: 1985 force compression

hmmmm, im really thinking about doing it myself now. I am really good with my hands and am not afraid to tackle things. Ill check into it and get back to you guys. The chylmers manual will walk me through everything? Ill get one of those first and see if its pretty cut and dry. Thanks Frank

Re: 1985 force compression

Jack Daniels said:

What do you guys think of a 83 85 FORCE outboard with 85 psi on all three cylinders? The majority of the compression readouts that i have seen usually have 120 psi or more. Is having 85 psi on my outboard acceptable or does it mean that im losing power and a rebuild might be in order. I can get her up to approximately 32 mph on a 16 foot bayliner. This is all the speed that i need considering i mainly tube and fish from it. Thanks guys.

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My 85 85hp has not been rebuilt, and it registers 130psi on all 3. The 85hp Force is pushing an '85 Bayliner 1600 Capri Cuddy (16 ft). On a very smooth, calm lake, I did a max of about 40mph trimmed fully in with just me and 9 gallons of gas. Can probably do better with a little trim adjustment. Out on the bay with fair weather, I was able to do 38mph, but I also had the Navy top on it, and that may cause some wind resistance, plus I had the kids and some gear.

If your Bayliner is a bow rider, it is a 120lbs or so lighter than my Cuddy Cabin. My guess is your horse power is suffering a bit from lower compression, and/or the boat is carrying a bigger load than I was and/or there is wet foam loading it down and/or your speedo is off and/or we have different pitch props.

BTW, the speeds were determined by the factory speedo (pitot style). But that shouldn't account for an 8 mph difference.

The bottom line is as long as its performance is consistant, then there is nothing to worry about. Although you are probably right that at 85psi, it is showing its age. Doesn't mean its going to blow up tomorrow, but it is worn, I would just use it as is as long as you can.

Re: 1985 force compression

The 32 MPH i had was with a typical speedo with two adults and two children. We were completely loaded down also. I know teh foam isnt saturated because earlier in the year we had the rear boards removed and replaced in addition we had the entire underside professionally inspected, so im good there. However when i first took it out fishing with just me and another guy we had it upwards of 35 to 36 mph. Which for me is plenty, just gunna run her until she needs rebuilt or i can upgrade. Thanks for all the info guys, i have no doubt shes getting old and thats probably the cause of the low compression. But from what you guys are saying, i have no reason to worry, yet.