Compression Check on 1987 Evinrude

[JWayne]

My 1987 140 evinrude runs great on the water at top end and idles fine. It just does not have much low end power. Tried different prop's and that did no tfix the problem. I checked the compression aand it was 90 in every cylinder. I know in a car this meand a rebuild is it the same for an out board or coul dit be something else.
Also haw hard is a rebuild. I have overhauled several car motors but just getting into boats

Thanks fo any info

 

[Barnacle_Bill]

Re: Need informaiton

Re: Need informaiton

We need to know how many RPMs you are turning at WOT. (wide open throttle) Can you elaborate a little more on the different props you tried? Whats on there and what you tried. Sizes.

 

[JWayne]

Compression Check on 1987 Evinrude

I have a 1987 140 Evinrude it runs great but does not have a lot of power on take off. Not the prop checked that I did a compression check and it showed 90 lbs on every cylinder does this mean a rebuild or could it be something else

thanks for any help

 

[tashasdaddy]

Re: Compression Check on 1987 Evinrude

suggest doing a decarb, but your compression is equal on all cylinders. have you check the boat, to make sure you are not carrying extra unwanted water weight? (saturated Foam?)

what kind of boat is it on? did you check spark on all cylinders?

Decarb, take a can of seafoam put 3/4 of it in the gas tank, with only 1 gallon of premixed gas. put the rest in a spray bottle. start the engine, and let it come up to temperature. then remove plugs, and them some real good shot of seafoam into the cylinders, replace plugs, let sit 15 minutes. restart, and spray the rest of the seafoam into the carbs, so the the motor almost stalls, wait and repeat until the seafoam is gone.then take for a wide open spin. then put in new plugs, ad premixed gas to the tank, and take it for a wide open throttle spin. it is going to smoke like a house on fire, during this process.

afterwards compression.recheck

 

[tashasdaddy]

Re: Compression Check on 1987 Evinrude

i have merge you threads, double posting is a not appreciated on the forum.

 

[jonesg]

Re: Need informaiton

Re: Need informaiton

My 1987 140 evinrude runs great on the water at top end and idles fine. It just does not have much low end power. Tried different prop's and that did no tfix the problem. I checked the compression aand it was 90 in every cylinder. I know in a car this meand a rebuild is it the same for an out board or coul dit be something else.
Also haw hard is a rebuild. I have overhauled several car motors but just getting into boats

Thanks fo any info

Its not bad compression, its even and thats good, follow Tash's directions for seafoaming, but it looks like the sluggishness is from something other than compression.

Boats are similar to planes, a 1000hp engine will go like the blazes on a rutan racer but fly like a dog on a bipeplane.

Hull design , outboard installation (skeg depth) and weight play a big role on a boats performance.

 

[JWayne]

Re: Compression Check on 1987 Evinrude

i have merge you threads, double posting is a not appreciated on the forum.

Sorry for the double post this is my first time to use these post sites but thanks for fixing it for me.


To follow up on some question that have been put out there. It is on a pro craft 1750 and it has a 23 pitch SS prop. I tried a 21 and and a 24 and it did not see a difference. As for RPM's the guage is broke but from listining it may not be at full RPM,s. Also all plugs look to have the same burn to them and the motor is an 89 if that make a differance.


Thanks again to all that are helping

 

[JWayne]

Re: Compression Check on 1987 Evinrude

Also it is not carring an extra water just rebuilt the floor and installed new foam pretty much through out the boat.

 

[tashasdaddy]

Re: Compression Check on 1987 Evinrude

your pitch is too high, for low end power, you have what use to be called a speed prop, you need a 19 inch pitch, this will get you out of the hole, and also good top end. you have to give a little on each end inorder to get both. also trimming you motor all the way down when getting out of the hole is necessary, then trim out.

 

[Benny1963]

Re: Compression Check on 1987 Evinrude

you need to get a good tach working ,to get help with setup
how high are you running your motor on transom ,know exact rpm will be the only way to start maxing your setup .have you checked to make sure your not dropping a cyl at load.it could be a lot of things you should have gained rpm dropping pitch,provideing you use the same type prop as not 4 blade or something,

 

[ezeke]

Re: Compression Check on 1987 Evinrude

I agree that you are over-pitch. If you put a 17 or 19 pitch on you probably won't be lugging your engine. Shoot for 5800 RPM at WOT with your normal workload.

 

[JWayne]

Re: Compression Check on 1987 Evinrude

The boat and motor came together when new at least all the number match the original sales ticket when it was bought new. These were mixed in with the other stuff I got when I bought the boat used. It does look like they put a spacer plate on the motor at some point but the motor it does not appear to be moved up or down. I will try going down to a 19 pitch prop and see what that does. If you think it is nothing major I will invest more in the boat and get all new guages for it. I just did not want to pour more money into it if it was going to need a major overhaul or a new motor. I have it trimed all the way down when I start and trim it up once it gets on plane.

Again thanks for the help

 

[JWayne]

Re: Compression Check on 1987 Evinrude

your pitch is too high, for low end power, you have what use to be called a speed prop, you need a 19 inch pitch, this will get you out of the hole, and also good top end. you have to give a little on each end inorder to get both. also trimming you motor all the way down when getting out of the hole is necessary, then trim out.

I now have done the de carb and still all six cylinders are at 89 to 90 on compression. Is that still ok I did notice the motor gaining rpms and I will be getting a new tach this week to check them. I will also be looking for a used 3 blade 19 pitch prop to see how that helps

Thanks Again for all everyone help on this

 

[Benny1963]

Re: Compression Check on 1987 Evinrude

those comps are good ,you may see a little more with some use .
have ya got ya a tach working

 

[JWayne]

Re: Compression Check on 1987 Evinrude

Hope to have one on it this week end

Thanks for the help