Spark issuse solved, now low compression in one cylinder

[CaneCutter79]

Re: Spark issuse solved, now low compression in one cylinder

The lows are supposed to be in the 50s tomorrow morning. We had a NICE cold front blow in here in NW Arkansas.

So, I got the motor put back together with all new gaskets (bypass, main head gasket and secondary) and I still have the same compression numbers. I'm going to test it on the water in the morning. I think the compression goes up when the motor is warm. I think I can get 80-90psi when it's warm.

The inside of the cylinder wall looks good when it's cleaned out. I used a little Seafoam spray to help free up the rings.

I'll report in my findings tomorrow. Wish me luck!

 

[CaneCutter79]

Re: Spark issuse solved, now low compression in one cylinder

Same compression numbers even when the motor is warmed up. The odd part is, the boat runs awesome. I'm getting better performance with one low cylinder than I did with all four being the same. Odd huh?

In a 15.2ft long modified V-hull (tri-hull variation) with two guys, me at 200 and my bud at 290, fishing gear, 2 full 6gal tanks of gas, 3 batteries, etc, I can still get 38-39mph. With me alone and no gear I can get 39-40. With good chop on the water, I can hold 40 and sometimes get 41-42mph.

When I first got this prop early this summer, I only got 37-38mph and with both of us, I got 36mph.


So, if it's safe to run the motor this way, I'm going to keep running it this fall and maybe this winter if I get time, I'll break down the powerhead and replace the ring in that one cylinder. Otherwise, I'll keep running it and keep an eye on the compression.


As it is now, the motor has lots of torque and great holeshots. Motor runs strong as an ox. GO figure.....

 

[Craig-]

Re: Spark issuse solved, now low compression in one cylinder

Same compression numbers even when the motor is warmed up. The odd part is, the boat runs awesome. I'm getting better performance with one low cylinder than I did with all four being the same. Odd huh?

Because the low cylinder is actually doing work now that the water is gone, where before it was just being pulled along by the others. Was really hoping to see a compression improvement as well. Keep monitoring it and watch the plugs for any sign of problems. Run it at it's sweet spot, avoid pushing it hard. You can use it as is, but 40-50psi low on one is a big variance, so go easy. What goes wrong next is piston slap, a knock you will hear, time to stop using it.

You did what it took to save it, congratulations for taking the leap. Changing the rings is a whole other story, you might want to find that last mechanic again, to help with that project. He sounded like a decent guy, you could save some labor cost by pulling and stripping the powerhead yourself and giving him some work in the off season.

 

[CaneCutter79]

Re: Spark issuse solved, now low compression in one cylinder

Since the weak cylinder does not have the same compression, it will cause excessive wear on the piston arm and the backside of the piston correct? That's the piston slap you're talking about right?

The motor is still tough to turn over when it's cold. The one cylinder acts like it's binding a little because the motor doesn't turn over as well on that one cylinder. Sounds like a weak battery but it's not the battery. When the motor is warm, it turns over great. That's what made me think the compression was better when it's warm.

Considering how fast and easy it was for me to get a low cylinder with no warning, I'm very reluctant to spend more money on repair because it could just as easily happen again. I'm just lucky I caught the low cylinder. I would have never checked my compression unless my spark issue hadn't have showed up.

 

[Craig-]

Re: Spark issuse solved, now low compression in one cylinder

Piston slap is when the piston itself hits the cylinder walls instead of just the rings. The piston runs up cocked at an angle and down at another angle instead of square up and down. This causes wear on the aluminum piston skirt first, wrist pin bore damage, then onto other problems. Your bad cylinder rings may be stuck in their groves or just one of them may be stuck. Spray some deep creep SeaFoam through the spark plug hole with motor tilted up to horizontal as possible and let soak, this may help them free.

 

[CaneCutter79]

Re: Spark issuse solved, now low compression in one cylinder

I did put some Seafoam in the cylinders before putting the new gasket on. I wiped down any excess on the cylinder and cylinder walls. I'm not sure how much made it to the rings so I'll try that again.

I assume I will be able to hear piston slap pretty easy correct?


By the way, I tested the audible warning horn. Its LOUD! Sounds like the strike buzzer on the Family Fued gameshow. There's no doubt you'll hear that lound buzzer even in a blinding rain at full throttle.

 

[Craig-]

Re: Spark issuse solved, now low compression in one cylinder

I assume I will be able to hear piston slap pretty easy correct?

Audible knock, sounds like it comes through flywheel.

 

[CaneCutter79]

Re: Spark issuse solved, now low compression in one cylinder

My fear is trying to break down the powerhead so I can replace the rings in the low cylinder and then still have the same issue because the cylinder or powerhead is warped.

I?d rather have a mechanic do it and that much work is really expensive. No one will ?just replace the rings? either. Everyone wants to do a rebuild or at least hone the block and put in a new cylinder. I understand why everyone wants to do this but it?s a lot of money for an older motor. My biggest fear is paying $1-2K for a rebuild only to have the issue re-appear a few years from now or a separate issue of significant cost because of it?s age.

It?s a real shame because it?s a great little motor and the boat is in terrific shape. It has a lot of sentimental value as well.

 

[Craig-]

Re: Spark issuse solved, now low compression in one cylinder

My fear is trying to break down the powerhead so I can replace the rings in the low cylinder and then still have the same issue because the cylinder or powerhead is warped.

I?d rather have a mechanic do it and that much work is really expensive. No one will ?just replace the rings? either. Everyone wants to do a rebuild or at least hone the block and put in a new cylinder. I understand why everyone wants to do this but it?s a lot of money for an older motor. My biggest fear is paying $1-2K for a rebuild only to have the issue re-appear a few years from now or a separate issue of significant cost because of it?s age.

It?s a real shame because it?s a great little motor and the boat is in terrific shape. It has a lot of sentimental value as well.

Yeah, just run it and go easy. If you start hearing a knock, things are getting worse.

 

[CaneCutter79]

Re: Spark issuse solved, now low compression in one cylinder

Yeah, just run it and go easy. If you start hearing a knock, things are getting worse.

By worse, you mean it's definately going to require a re-hone and slightly oversized cylinder?

I've run the motor once since my last post on this thread and I do not plan on running it again. It's just getting worse which makes it more expensive. I was told once you get to 50-60psi, it's going to need an oversized cylinder or re-hone at least.

Wish I could just replace the rings and not rebuild the motor.

 

[levi_tsk]

Re: Bad coil or failing power pack??

Re: Bad coil or failing power pack??

]you shouldnt need ANY solder pull the boot off of the old plug wire theres a spring with a sharp end on it stab it through the side of the new plug wire spit into the new boot and slide the plug wire and spring into the new boot this way if you f up the end of the plug wire later youll just cut a little off and repeat instead of fighting trying to get one of those clamp on type ends back on in a swell

also what you discribed sounds like youve got a power pack on the frits and having owned this EXACT engine id say more than likely thats part of the problem wholesale marine sells sierra power packs for 53.00 iboats will match that price and their shipping is cheaper youll have to call em to get it matched though.

it also sounds to me like you need a carb job id do this FIRST mine did the same crap over the summer this guys got full carb kit on the cheap and its OEM i just got two from him for my boat hes a super nice guy and if you need anything else he can get it just tell him your model number and serial number

your lower carb is gummed up no doubt but id do both while i had it apart they are simple to do and if you need ANY help im here for you bro i got pics and a service manual for your motor IF you need em

http://cgi.ebay.com/ebaymotors/ws/e...0601032893&viewitem=&sspagename=STRK:MEWNX:IT

DO NOT RUN THIS MOTOR AGAIN UNTIL YOU DO THAT CARB YOU WILL BLOW UP YOUR ENGINE!!!!!!!!!!!!!!!!!!!!!!!

 

[carolinabanks]

Re: Spark issuse solved, now low compression in one cylinder

First sorry for your prob but I have a issue know I'm prob posting in the wrong area but I just bought a old Johnson out board I don't know year or model number but i did get a number off the power block but I can't find and info from this number and I tried to fire the motor and plenty of fuel but no spark now I'm tryin to fix this prob but not knowing the year or model has got me stuck the number on the little silver plug is j3453335 plz any info will help and sorry if I post in the wrong place I'm a grease monkey on trucks not a computer guy

 

[AlTn]

Re: Spark issuse solved, now low compression in one cylinder

first page..dark blue box that reads...Post New Thread...ask you question in the title...like.. "help with motor id"...in the body part just state what you know...letters, numbers, no. of cylinders, post photos if you have any...got to know what's being worked on before spark question can be addressed

 

[CaneCutter79]

Re: Bad coil or failing power pack??

Re: Bad coil or failing power pack??

http://cgi.ebay.com/ebaymotors/ws/e...0601032893&viewitem=&sspagename=STRK:MEWNX:IT

DO NOT RUN THIS MOTOR AGAIN UNTIL YOU DO THAT CARB YOU WILL BLOW UP YOUR ENGINE!!!!!!!!!!!!!!!!!!!!!!!

I have bigger issues that a carb rebuild. Potential motor rebuild. See the most recent post above that was posted yesterday. A carb rebuild is already on my radar to do ASAP. I?m trying to find out if a rebuild is really needed, do I need to hone the cylinder walls, or do I just need to replace the rings to solve the compression issue which is WAY more expensive than a carb rebuild.

 

[wilde1j]

Re: Bad coil or failing power pack??

Re: Bad coil or failing power pack??

Decarbonizers (Deep Creep, etc.) only work on a hot, running motor. Dumping it in to a static motor does zip.

You won't know what will be needed for a rebuild until the motor is torn down, the bores miked and checked for roundness, etc. Honing is seldom useful alone. Most of the time the holes will need boring, etc. and the oversize will result from measurments.