90 hp 2 stroke low compression break in time

[patrack]

I have a 1990 70 hp 2 stroke johnson 3 cylinder I replaced the #2 cylinder ran oil in fuel and vro as prescribed engine idle perfect timing top and bottom dead on. got to lake # 3 carb float stuck at dock took a few minutes to figure out and fix. The engine now runs rough at idle but smooths out at about 1500 rpm. after running for several days engine progressively running better switched to regular gas after 10 gallons of fuel. Still rough idle. #3 piston good compression #2 a little less #1 a little less than #2. Now granted this is thumb over hole test. Looked in cylinders through spark hole they are mirror clean. Pulling the wire when running backs up thumb over hole results. I know I can damage ignition.

It runs like a scalded ape I took it to full throttle after about 8 hrs of break in time. My question is Did the # 3 cylinder seat because of the extra fuel it got when the carb over flowed and is it normal for the pistons to take a while to build to full compression? It seems the more I run it the better it runs so should I just ignore the compression thing and just run it.

This is my first boat

 

[jerryjerry05]

Re: 90 hp 2 stroke low compression break in time

Why the rebuild?? Profile,location? You might be close to someone who can help.
The VRO still working? Personally I don't trust them.
No the cylinders should all be the same.The cylinders should be ready as soon as you start them,no seting in time. There is a breakin period but you've done that.
Your finger is for pointing and scraping icing off the cake.
You need a comp tester!!
IF THERE IS ANY DOUBT????? Check it out???
The air screws set right?

 

[JB]

Re: 90 hp 2 stroke low compression break in time

After you get a good comp tester, go here:

http://forums.iboats.com/engine-frequently-asked-questions-faq/compression-test-jb-391323.html

 

[JDusza]

Re: 90 hp 2 stroke low compression break in time

Got model and serial numbers? The first 1990, 90 hp I looked at was a 4 cylinder.....

 

[emdsapmgr]

Re: 90 hp 2 stroke low compression break in time

When breaking an engine in, there is a period where it is recommended to use double oil for break in. My experience is that once the recommended (double-oil) break-in period is over, the engine may still continue to increase compression slightly for some period of time. I always take a compression reading after I first fire a rebuilt engine, as a baseline measurement. Then a few months later after it's been run a bit. And usually at the start of the season every year to two after that. I keep track of the readings in the engine's service manual.

 

[V153]

Re: 90 hp 2 stroke low compression break in time

Got model and serial numbers? The first 1990, 90 hp I looked at was a 4 cylinder.....

OMC didn't build a 90hp 3cyl. Believe the 75 Stinger was the biggest I3 ...?

 

[JB]

Re: 90 hp 2 stroke low compression break in time

Give us a model number, patrack. There never was a three cylinder Johnson 90. Other brands made triple 90s. You may have a typo or confusion about the make or HP.

 

[boobie]

Re: 90 hp 2 stroke low compression break in time

Agree + 1..........Never heard of a 90 hp 3 cyl OMC either.

 

[patrack]

Re: 90 hp 2 stroke low compression break in time

Got model and serial numbers? The first 1990, 90 hp I looked at was a 4 cylinder.....

I'm sorry fog on the brain 70 hp its a 70 tlesb 2 stroke 3 cyclinder
air screws are set at 1 1/2 turns and I had to rebuild it after a ring stuck and guald number 2 cylinder. It had been sitting for 2 years. yes the vro is working and the alarms work. I am thinking maybe I should get rid of the champion plugs I have never had much luck with them thoughts

 

[JB]

Re: 90 hp 2 stroke low compression break in time

JohnnyRudes have been designed for, and specified, Champions since the Mayflower. Even plugs that are advertised as equivalent are not; there are subtle differences.

Trust the engineers who designed it and use the plugs they specify.

 

[JDusza]

Re: 90 hp 2 stroke low compression break in time

I have a hard time believing #2 was galled from sitting. Did the rings on #2 come out in pieces?
I'd be concerned the VRO is not putting out at rate and #2 is running dry.
And, there's more here than meets the eye. First boat, ..... need to review newbie info in Top Secret File. Someone here will bring you the link. At the top of this forum is the file and inside you'll find what to do after the engine's been sitting.
Your question about seating in the #3 cylinder....did you replace the rings in #3? I thought you were breaking in #2.
After rings are installed, they will "break-in" and seat themselves to the characteristics of the cylinder. Compression and performance will improve with time to some optimum point. Then the performance will remain constant.
The thumb test for compression is humble and not reliable if you're questioning numbers from cylinder to cylinder.
My advice? RUN IT. Two strokes want to run. They need to run.

Your plugs are good. Champions are great. I'd pull new-fangled, rim fired BS jobbies out. Nothing there for the $$$ except nice packaging. After you've run hot for 20 minutes, pull the plugs as immediately as you can and check their color. Should be toasty brown. Watch out. They'll be HOT.

Idling rough is your carburetion..... you're choking up at low rpm. #3 already stuck on you....... Engine sitting a couple years?, your low speed carb circuit is gummed up. Run an additive in your fuel, Techron or SeaFoam. This might clean it up the carbs without taking them off.
psst......dump the VRO.........
J

 

[Fleetwin]

Re: 90 hp 2 stroke low compression break in time

JohnnyRudes have been designed for, and specified, Champions since the Mayflower. Even plugs that are advertised as equivalent are not; there are subtle differences.

Trust the engineers who designed it and use the plugs they specify.

Yes +1 on the Champs.

The Oil Injection mixes oil/fuel BEFORE the carbs. so one cannot run lean on oil. The oil injection is quite reliable, as long as it is maintained (fresh oil, drain the tank periodically).

Unless you know exactly what your compression numbers are, you're guessing.

 

[patrack]

Re: 90 hp 2 stroke low compression break in time

#2 was destroyed I had to bore 30 over rings came apart I have already cleaned the carbs. They were clean to start with turns out the plugs fouled. tach was off turns out 1500 rpm is actually about 900 which it purrs at so now I have it set at right rpms and it purrs. The local shop tellls me to give it some more time for the other cylinders to seat they were honed and new rings compression is good at the right rpms but 2 of the plugs had fouled from the oil. I rebuilt vro and replaced all hoses so looks like I'll just run her

 

[patrack]

Re: 90 hp 2 stroke low compression break in time

update.... After putting the pieces together and thinking about it here we go. It was idling perfect then the #3 carb overflowed and it started running rough, fixed it and it started running rough after that at idle. #1 and #2 respond slow to mix screw adjustment and made very little change when their plug wire was removed briefly while running. I used compressed air to blow out #1,2 idle screw mix and replaced fouled champions with new champions. When I rebuilt the motor I had replace the fuel lines,filters and primer bulb except for the line inside the motor. I believe I probably got some grime in the fuel line after the filters and it took a little while for it to break free and hit the carbs It sounds pretty good now with the muffs on in the back yard still has a little roughness but I will add some seafoam to it and give it a work out this weekend got a tube to pull and a kid to flip Thanks every one

 

[emdsapmgr]

Re: 90 hp 2 stroke low compression break in time

It's always good to do an autopsy on the engine to determine the original cause of the failure. That way when you reassemble it, you can correct it before any damage is done to the new powerhead. Just to be sure, you might want to pull the plugs after every hour for a while and check their color so that they all look the same. When the plugs are out, shine a pencil light in the spark plug hole and visually check the color of the crown of the piston-hopefully they all look the same.

 

[patrack]

Re: 90 hp 2 stroke low compression break in time

I did and they all looked the same and the cylinder wall,what I could see of it was smooth which was a big relief. I had never rebuilt a two stroke let alone an outboard. Well I should say Reassemble as I only replaces 1 piston. It was very hard to get to some of the bolts to torque them and I used best feel on a few. I live in the desert on a dirt road with lots of traffic and keeping it clean was a big challenge. I also assembled it 3 time before I got it right.1st attempt I forgot to use sealant on case!! No Coffee moment. 2nd realized I may have put a bearing in backwards. 3rd time I was so confident I was done, next morning walk back out to shop and what do I see on the floor but a solitary wrist pin needle bearing from the number 2 cylinder. Thanks everyone for the advise and help if you every find yourselves in arizona my barbeque is always ready.

 

[emdsapmgr]

Re: 90 hp 2 stroke low compression break in time

All of us have had similar experiences. The thing is that you found your own mistakes. I admire your perseverence.