lower compression on#2 ,#3 cylinders on 125 hp

[kfouryou]

hi guy I have a 87 125 hp force and just had a spring tune done on it .The mechanic told me I have a compression of 150 on #1 and# 4 and 135 on# 2 and# 3 .He told me I shouldn't be concerned telling me the center 2 cylinders usually run hotter and thats why this is happening . Should I be concerned more than he's implying. Any imput would be appreciated

 

[danny9696]

Re: lower compression on 2 ,3 cylinders

Re: lower compression on 2 ,3 cylinders

I really can?t tell you to much of why, but I have an 89 force 125 and my compression is 120 on all four, I would be wondering why simply because that?s a big difference from 150 to 135, I know some of the guys here can tell you if it?s out of speck, I had one cylinder that was low last year and one of the guys here had me run some sea foam through and it brought it back up, may be worth a shot, I ran a can of sea foam in my fuel and sprayed my cylinders with deep creep the night before and took it out the next day it smoked bad but it did help me, it cleans carbon out, good luck

 

[kfouryou]

Re: lower compression on 2 ,3 cylinders

Re: lower compression on 2 ,3 cylinders

I'll add to my list ,thanks I just thought the numbers were odd is all,considering it's more then 10%.

 

[john from md]

Re: lower compression on#2 ,#3 cylinders on 125 hp

Do a complete decarb in accordance with the instructions in the maintenance forum FAQ. It is on page 2. Then check your compression. If you haven't been doing decarbs every season, then it may take two to loosen up your rings.

John

 

[kfouryou]

Re: lower compression on#2 ,#3 cylinders on 125 hp

thanks john I was hoping you would chime in you seem to always have valuable info I just got the boat last summer ,so I don't know if the previous owner did or not.I just have to wait to get my starter checked seems the armature was shorting out on the housing .

 

[john from md]

Re: lower compression on#2 ,#3 cylinders on 125 hp

That usually happens when people use the starter too much and it overheats. When they overheat, the varnish on the windings melts and shorts out.

Ebay has good starters for reasonable money.

John

 

[JB]

Re: lower compression on#2 ,#3 cylinders on 125 hp

This is the season for outboard hypochondria, K4U.

Your numbers are fine. Last time I checked 15psi (difference) can be seen as 10% of the 150psi top. Actually, any difference less than 15% is okay in most books.

A decarb treatment probably wouldn't hurt it, but it probably wouldn't change things in any useful way, either.

 

[kfouryou]

Re: lower compression on#2 ,#3 cylinders on 125 hp

thanks jb I'm gonna try a decarb as soon as my starters done .I actually checked my numbers it was 130 and 150 ,not 135 .I guess well see after the decarb

 

[jerryjerry05]

Re: lower compression on#2 ,#3 cylinders on 125 hp

Any so called mech that says low compression on 2 of 4 cylinders is ok or it's because they get hotter should be suspected of being stuupid.
If bad compression was ok they wouldn't put rings in the mix.
Anytime there is a variance in compression,that should be taken as a sign something BAD is gonna happen.J

 

[kfouryou]

Re: lower compression on#2 ,#3 cylinders on 125 hp

can anyone give me some common causes for this ,maybe rings or head gasket. These motor s have been around a while so I'm sure the probs are pretty much common for each. Should I do a leak down ?

 

[john from md]

Re: lower compression on#2 ,#3 cylinders on 125 hp

Two stoke engines, by their nature, carbon up over time. Newer injected engines combined with better oil makes for less carbon buildup than older engines.

Your rings are probably carboned up just from using the engine without doing a decarb periodically. If you do a couple of decarbs, letting the seafoam sit and work for a while, and your compression doesn't come up, then you could be looking at mechanical wear. If your head gasket was leaking, it would give signs such as low power, leaks, steam, water on plugs, rusty plugs etc.

John

 

[kfouryou]

Re: lower compression on#2 ,#3 cylinders on 125 hp

the guy I took it too said he put some kind of carb cleaner in the tank but I'll be putting in some seafoam also.

 

[huskerdaninva]

Re: lower compression on#2 ,#3 cylinders on 125 hp

I'm going to chime in here and perhaps I shouldn't, but here goes... Maybe I imagined this but I seem to recall reading a post on here a while ago about some of the four cylinder motors purposely were designed to have lower compression numbers on #2 & #3? Again, maybe I'm losing it (however that in itself implies that I had "it" at one time!) but that is what I recall or something to that effect.

 

[pnwboat]

Re: lower compression on#2 ,#3 cylinders on 125 hp

Here is a page from the Clymer manual that shows compression values for various engines. At the bottom of the page it has a note about "staggered compression".

 

[john from md]

Re: lower compression on#2 ,#3 cylinders on 125 hp

Er, guys, we are talking about an 87 125 not the later 90 and 120 engines. There is no staggered compression on the early engines. The low compression has to be from carbon, mechanical wear or a leaking head gasket. Hopefully it is just carbon.

John

 

[wan2live]

Re: lower compression on#2 ,#3 cylinders on 125 hp

I also have a 87 Force 125 and this is what I found after purchasing my boat.


I had low compression in #3 and #4 I took the great advice here to rule out stuck pistons and tried to decarb, that was a no go so I finally pulled the head cover to find that my head gasket was blown near #3 and #4 and I proptly ordered a replacement.

I completed the reinstall today and all my Cylinders are of = compression.
I also found out that one of the bolt holes had stripped threads so I went to Napa and bought a kit to correct that, this may have been what caused the gasket to blow in the first place.

If the decarb does not work check your head gasket you never know and it a very simple job to do.

 

[kfouryou]

Re: lower compression on#2 ,#3 cylinders on 125 hp

I will definately keep that in mind ,I guess I'll start from the basics of decarb first

 

[wan2live]

Re: lower compression on#2 ,#3 cylinders on 125 hp

I will definately keep that in mind ,I guess I'll start from the basics of decarb first

Good luck to you and I hope that it is as simple as my problem.

If you end up needing a head gasket I found mine on ebay and it was a great price and I got it fast.

http://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?ViewItem&item=280319815736&viewitem=&sspagename=STRK%3AMEWNX%3AIT

 

[kfouryou]

Re: lower compression on#2 ,#3 cylinders on 125 hp

thanks for the ebay page.