1987 mercury force 85 hp does not want start and backfiring

[JB]

Re: 1987 mercury force 85 hp does not want start and backfiring

SEE bad compression.

1ST rule!!!!!!!!!!!!!!!!! Do compression test FIRST!!!!!!!!!!!!!!!!!! Then all other tests follow!!!!!!!!!!!!!
It needs EVEN compression all cylinders to operate.It causes back pressure, backfiring,mis-firing etc.J

Sorry, friend. I do not agree with this theory. I have seen too many triple outboards with a bad cylinder start and seem to run okay until load was applied. I have never seen a true backfire from an outboard that was correctly timed.

Pan has now destroyed his engine trying neurosurgery to cure a headache.

 

[jerryjerry05]

Re: 1987 mercury force 85 hp does not want start and backfiring

I post here from MY experience.I have worked on hundreds of Force/Chrysler motors.
The way I learned from the factory and practical experience was to do a compression test FIRST!!!!
Then go down the other roads.
I don't want to get into a whizzin match,but that was the way to diagnose this problem.
If you don't want my experience on here just say so.J

 

[kend301]

Re: 1987 mercury force 85 hp does not want start and backfiring

I have to back up JJ05 here , In all my years in the automotive industry as well as building race engines for 14 plus years , A compression test is very important to determine if you have an internal failure that could get worse by still trying to run the motor . In fact when one of my motors had a miss , The first thing I wanted to know was dry and "wet" compression readings !

Keep posting JJ05 !!!

 

[O.T.Water]

Re: 1987 mercury force 85 hp does not want start and backfiring

Ditto, seems that Pan finally realized an internal fault by doing the comp test.

 

[JB]

Re: 1987 mercury force 85 hp does not want start and backfiring

I think you misunderstood me, guys. I did not say you were wrong.

The man complained about non starting and backfiring. You are experienced enough to know that a triple is three, mostly seperate, engines that share only a crankshaft and an ignition system.

A compression test showed one sick and two apparently sound cylinders. You seemed to be claiming that the low compression in #2 was preventing #1 and #3 from starting and was somehow causing the backfire.

I contend that the reported symptoms and the compression problem were coincidental. It had both, but one did not cause the other.

Now, understand that we are presenting differing theories here, not conflicting facts. We are both working with the facts of our experience to construct theories of what was wrong.

I have been messing with outboards for about 60 years, building racing 2 stroke engines for about 10 of them. I have learned a thing or three about them myself.

I had a CAT scan about a year ago trying to find out what was causing a GI problem. They found an abdominal aortic aneurism. Now they want to cut me, but they are quite sure that the AAA didn't cause the bellyache, which finally went away when I discontinued a medicine. I will not allow them to cut me because my likelihood of surviving it is too low.

I can't help seeing a similarity.

 

[Pan84]

Re: 1987 mercury force 85 hp does not want start and backfiring

I dont check compression first, because guy said it was 130 on these engine, but engine was not run one year. Yes it is my fault. And i found why backfiring, 2 wires from cd unit to coils was wrong

 

[tashasdaddy]

Re: 1987 mercury force 85 hp does not want start and backfiring

totally agree with JB, i have had many 3 cylinders run on 2 cylinder, with no compression on the third. and V4's cylinders run on only one bank.

 

[Don S]

Re: 1987 mercury force 85 hp does not want start and backfiring

To be quite honest, I find a compression test on an engine that has set for a year without running is a waste of time. Rings stick from setting and doing nothing, and low compression will not cause a loud backfire as Pan said he had.
I also know of no training that says the first thing you do is check compression.
Usually the first thing to do is a visual check of things and see if you can find out what happened just before the problem occured.
I personally had a Mariner V6 that a guy brought in. Said it wouldn't start and backfired a lot. He said it ran good before he worked on it. He had replaced the head gaskets and done some painting because of corrosion. After a bit of looking, found the plate that the coils were mounted on put on upside down. The guy was mortified when I told him.
Compression test wouldn't have told me a thing about the problem.

 

[kend301]

Re: 1987 mercury force 85 hp does not want start and backfiring

Lets get this thread back on track , JB and I talked for an hour on the phone tonight and we were both right just looking at things from diffrent perspectives and taking a diffrent set of "givens" into consideration.

The bottom line is to help Pan84 get his motor right .

Nobody misled him and he did what he did on his own , Now lets band together and help this guy out as much as we can !

 

[Stachi]

Re: 1987 mercury force 85 hp does not want start and backfiring

I am curious how he broke the head into five pieces and bent the block....if the bolts broke....wouldn't the head just lift off ??

 

[Pan84]

Re: 1987 mercury force 85 hp does not want start and backfiring

I am curious how he broke the head into five pieces and bent the block....if the bolts broke....wouldn't the head just lift off ??

Yes right, just lift off You tried move 21 year old bolt on the motor, which was used in salt water, when bolt and cylinder head already one piece? I tried spray wd 40 and heat up, nothing helped

 

[Stachi]

Re: 1987 mercury force 85 hp does not want start and backfiring

yes I have....from all the chips in the head around the outer edges of the lower bolts (in the picture), it looks like ya might have gotten a bit frustrated ....thats when you should come back here and ask for help....many of us have been there many times with rusty / corroded bolts and frozen parts, and have tricks that work on them...I didn't mean to offend you , I am a better mechanic than I am a statesmen...welcome to the forum and best of luck with your project.

 

[Pan84]

Re: 1987 mercury force 85 hp does not want start and backfiring

What kind of lubricant using for bolts, when put all together? anti seize or graphite lubricant?

 

[anewlife1]

Re: 1987 mercury force 85 hp does not want start and backfiring

Jerry Jerry

I don't know if this is your name, but I am really in some need of advise. I have a 1987 Force 85hp and it backfires a lot. We checked the Compression and is 121/122/120. We rebuilt the carbs and it still does not run worth a poop. It constantly backfires or Spits out the exhaust which will shut it off and we are kind of out of ideas. Can you maybe give us some advice? Thanks. I can be reached at merrytoonz@hotmail.com and my name is Brian

 

[Pan84]

Re: 1987 mercury force 85 hp does not want start and backfiring

Jerry Jerry

I don't know if this is your name, but I am really in some need of advise. I have a 1987 Force 85hp and it backfires a lot. We checked the Compression and is 121/122/120. We rebuilt the carbs and it still does not run worth a poop. It constantly backfires or Spits out the exhaust which will shut it off and we are kind of out of ideas. Can you maybe give us some advice? Thanks. I can be reached at merrytoonz@hotmail.com and my name is Brian

Try switch spark plug wires 1 and 2, I had same problem (first to second and second to first)

 

[emoney]

Re: 1987 mercury force 85 hp does not want start and backfiring

@ anewlife1: If you start a new thread stating the above you have a better chance of it being seen and relied to quicker.

Welcome to iboats, btw. Hey, Pan, did you get this motor rebuilt and firing?

 

[jerryjerry05]

Re: 1987 mercury force 85 hp does not want start and backfiring

Anewlife 1
Start your own thread.
There is a wiring diagram on the top of the motor.
Check this and see if it's wired right.
Then check the carbs,cleaned and the floats and air screws set right.
Check the reeds when you have the carbs off.
You should never put your e-mail in the posts.
Send private messages for that.J