1991 70 HP Force low compression

[eavdic]

Hi,
This is great Forum, I want to buy a 1991 70HP Force outboard motor which they guy says #2 cylinder has 30 psi compression. Wondering what could it be and how much to fix and where to get a service manual if I want to fix my self.
Thank You very much ...

 

[roscoe]

Re: 1991 70 HP Force low compression

Welcome to iboats.

What could it be?
Blown head gasket.
broken rings.
hole in cylinder
scored cylinder walls.
broken connecting rod, spun bearings, damaged head,

Will run you between $50 and $1200 for parts, depending on the damage.

Pull the head before you buy, inspect the damage, base the price on the damage.

OEM manuals are often on ebay.
Clymer makes a decent manual for Force motors.

Its not worth more than $100 as it sits, without knowing the damage.

 

[eavdic]

Re: 1991 70 HP Force low compression

Thank You very much for your quick reply...Its 1991 Bayliner Capri open Bow looks in decent shape for $800 I think that is a good deal. You? Would you be able to tell if cylinder cracked if you just pull the plastic cover off. Sorry not familiar with these engines at all. How hard would it be to replace the ring on that cylinder. And final question is can I put 95 HP Mercury Thunderbolt Ignition on this boat and is it hard to swap the engines. Guy is selling the whole boat with this Mercury engine on it so all connections should be there.

Thank you

 

[jerryjerry05]

Re: 1991 70 HP Force low compression

Force connection and connectors might not be the same.
You need to pull the head and check for damage.Then we can quote $$$.
It could be as little as $35 for a new head gasket.Or $1500 for a rebuild.J

 

[eavdic]

Re: 1991 70 HP Force low compression

So how could I find out which motor other than the one I have would fit my boat. The vin #BIYA39CVI091 so that I could look for those and get one.
Also do you guys have any idea where I could get parts for this thing .

 

[roscoe]

Re: 1991 70 HP Force low compression

There should be a US Coast Guard rating sticker near the steering wheel somewhere.
It will tell you the largest motor that can be used on the boat.

As far as what brand of motor, take your pick.
You may have to change the throttle controls and cables, but any brand motor will work on the boat.

THe Bayliner Capri was available in 14' thru 20' lengths.

Looking for parts for the boat? ebay and craigslist

parts for the motor, ebay, Mercury dealers, many online retailers.

 

[eavdic]

Re: 1991 70 HP Force low compression

Ok got the boat today...here is what is going on. I got is started with chochke starts right up but when Idling it shuts of. If I put it in gear forward it seems to do fine only idling is the problem. Also I checked compression on cylinders and #1=120 #2= 90 #3=120 not sure what could cause this.
Also when I ran it I put a big bucket of water and after I while I had it running I could see oil float around in the bucket ..(Is that Normal)..when it runs it looks like white somoke is coming from the enigine not a lot but noticable.
This is what I did I had it running to warm up....after 15 min I sprayed sea foam in the carburator for a while until it shut down by it self. After that I took out the spark plugs and sprayed a lot of sea foam in all three spark plug holes put the spark plugs back and let it sit for about 20 min after that I restart it and had it running for about 15 min checked the compression and it was same 90 psi on the 2nd cylinder. What do you guys think I should be looking for I have ordered a manual for it I am hoping to get it fixed myself
Thank You very much

 

[eavdic]

Re: 1991 70 HP Force low compression

I can send pictures if needed

 

[eavdic]

Re: 1991 70 HP Force low compression

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IMG]http://i890.photobucket.com/albums/ac105/avdicemir/Boat/IMG_04531.jpg[/IMG]
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IMG]http://i890.photobucket.com/albums/ac105/avdicemir/Boat/IMG_04481.jpg[/IMG]
IMG]http://i890.photobucket.com/albums/ac105/avdicemir/Boat/IMG_04501.jpg[/IMG]

 

[roscoe]

Re: 1991 70 HP Force low compression

I would pull the head off and examine the head gasket, cylinder, piston, rings.

Looks like someone has already had the head off, so hopefully the bolts will come out without breaking.

Oil - normal
smoke - normal

How did the plugs look when you removed them?

 

[eavdic]

Re: 1991 70 HP Force low compression

Pulled the head off, head gasket looks good, however thye cylinder has bulge on it on the outside. the inside of the cylinder does not look like it has scratches is it done..do I need to rebuild this thing

 

[roscoe]

Re: 1991 70 HP Force low compression

Are the rings still intact?
no missing pieces?
Rings stuck?

Need to find cause of low compression before you know what to replace.

photos?

 

[eavdic]

Re: 1991 70 HP Force low compression

Hi Roscoe, thank you very much for your replies,
I took the head of the motor and took to mechanic to check out see how much to replace or if it was fixable at all. If I turn engine the cylinder moves freely no issues how ever the mechanic thinks its something that went into the carburator and damaged the cylinder. The cylinder wall has small scratch that goes strait into the enigine...he said he would be able to hone it out and replace cylinder with ring replace all seals and would charge me around $1300.00 parts only about $200 . I thought that was little excessive on top of that I want to be able to service the eninge my self so I want to do it. I have started to take the motor apart will see how the cylinder looks.
I tried to post these pictures on here but it does not let me. I can email them that would be big help. Another question I have is when I took the cover of the cylinder I could see the cylinder head could I just Unscrew the cylinder whithout taking the whole engine apart.

 

[eavdic]

Re: 1991 70 HP Force low compression

here are the pictures ...thank you very much for your responses As you see the cylinder in the engine is it possible just to take it out as is or do I have to take the whole engine apart. And can I hone the cylinder, do I need any special tools or will sand paper do. And final if I do hone it do I need to buy the original piston with ring or does it have to be bigger size.

 

[roscoe]

Re: 1991 70 HP Force low compression

Doesn't look too bad, unless I am missing something.
You may be able to remove the piston without a complete tear down.
I know it can be done on some motors. You may be able to use stock piston size if oversized rings are available.

I am going to refer you to Frank for further rebuilding advice. I have little experience in total rebuilds.

I would start a new thread titled "help with rebuild". Possible send Frank a pm and ask for help.

 

[jerryjerry05]

Re: 1991 70 HP Force low compression

Fill out the profile.You might be close to someone who can help.
The buldges in the piston would worry me.
If your mechanically inclined then you can do this yourself.Post a pic of the head gasket.J

 

[eavdic]

Re: 1991 70 HP Force low compression

Thank You guys, here is the picture of the head gasket, now the pistons themselves have no stamped writing on them whatso ever but the head does it says 030 does theat mean the head was rebuilt and bored to .30 already I don't know why it would say that..now I don't know what piston to get..hm any advice?

 

[jerryjerry05]

Re: 1991 70 HP Force low compression

Those would be standard pistons.The head marked 030 where?J

 

[eavdic]

Re: 1991 70 HP Force low compression

First Let me thank you guys very very very much,,, I replaced the rings my self thru the reevs i did the whole thing on Friday. Honed the middle cylinder and replaced orig. rings. The whole thing cost me around $100.00 Unbelievable. I could not believe I did it my self . ...very easy to do. I have compression of 130-135 in all three cylinders. I took the boat for test drive yesterday morning it did well. I did have to adjust the carburator a little so what I did Is I turned the screw all the way in and then backed it out two total 360 degree turns. engine seems it runs fine ( is that what I should have done)? I also did change the oil in the lower or should I say prop..so far so good.

 

[eavdic]

Re: 1991 70 HP Force low compression

Trying to change the lower unit oil and I found 4 plugs which one is which please help....