causes of engine failure

[muskiedaze]

greetings. i'm new to this board and think its great the way you guys help each other out. I'm a fishing guide and run 2 boats. I have a 2 stroke 50 HP Merc tiller on a 16 ft V-hull for the lake and a 50/35 johnson jet on a tunnel hull for the river. granted, I put on a lot of hours, but my repair bills have been insane. These motors are like a nightmare that never ends. For example, one month out of warrenty the merc seizes up. after 12 trips to the dealer he finally figures out that someone at the factory forgot to bend a lock tab on a bolt on the reed valve and it backed off into the crank. Dead motor. Merc coughed up a new power head for me but it still cost 500 bux to install it, and six more trips back to the dealer to get it running. (he left a plastic plug in the block some where and it took a factory rep guy to figure it out)then the stator went south. then this, then that.<br />The Jet's older and has been even costlier. here's a partial list of the things that have broken on the Johnson: drive shaft, engine mounts, tilt piston, fuel and oil pumps, control box,etc. etc. OK, you get the idea. I'm done whinning.<br />Now the latest. #2 piston burned up on the johnson and I have decided to become a marine mechanic. I had the cylinders bored and I purchased about 600 bux worth of pistons, gaskets and bearings. My concern is that I can't see what went wrong. There was lots of bearing wear. the piston looked like it was burning for a long time. the plastic cage on the center bearing was pretty much gone. no air leaks that I could see. #1 cylinder wasn't carboned up at all. Any ideas on what to look for? Thanks, I'll let you know how it goes.<br /><br />John

 

[JB]

Re: causes of engine failure

Ahoy, MuskieDaze.<br /><br />You seem to have had a lot more than your share of failures, but the variety suggests that you aren't doing anything wrong.<br /><br />Why do engines fail? Well, piston-cylinder failures are most likely when you have multiple carbs that are not feeding identical mixtures to their cylinders. One carb gets a little gum and starts running one cylinder a bit lean. If you don't notice you will soon be out one cylinder.<br /><br />Theoretically very close monitoring of engine performance and temps could prevent this, but I am not sure that the extra instrumentation would be practical.<br /><br />Fanatical care of your fuel system and carbs will increase the average life of your engine, but, well, stuff happens.<br /><br />Good luck.<br /><br />Red sky at night. . .<br />JB

 

[ODDD1]

Re: causes of engine failure

Some days every time you turn around, something else has hit the floor........I hope your streak is at an end...

 

[muskiedaze]

Re: causes of engine failure

Thanks, guys. I fully expect things to continue to wear out and break down. Thats why I've decided to try and learn how to work on this stuff myself. I'm opimistically giving myself a 1 in 3 chance of having my first engine re-build hold together. hmmm...maybe a rowboat. <br />John

 

[rolmops]

Re: causes of engine failure

Hello.<br />Around here on lake Ontario those guides that have a high volume and use outboards have mostly returned to a 1:32 mix listening to the local guru of outboards.This "Guru" who has been an outboard mechanic since the late thirties claims that he only started seeing cylinder trouble like schorched cylinders and the like since people started using 1:50 mix.He runs the boat fuel gas station in the outlet of Irondiquoit bay and the only mix he is willing to pump is 1:32.The results are remarkable.He still fixes schorched engines but only from 1:50 users.So maybe it means a tad more smoke but it helps you keeping the green stuff in your pocket.Good luck.

 

[muskiedaze]

Re: causes of engine failure

rol, are you suggesting useing 32:1 mix instead of relying on an oil injection system? It would be safer, i agree, but wouldn't i foul plugs often and sit in a cloud of smoke when trolling all day at low RPM? <br />Thanks,<br />john

 

[alcan]

Re: causes of engine failure

Hi Muskiedaze<br />Sorry to hear of your troubles. From what you describe, it sounds like you johnson didn't get enough oil. I personly don't trust anybodies oil injection system. I didn't trust it when it came out on motor cycles ether. I know, I am old school. Maybe when your drive shaft broke, it was replaced with one a bit to long. Caused by improper shimming,newbearing,etc. This could cause a pre-load to the crank. As far as smoke is conserned, most manufactures recomend double oil for break-in period, that is 25:1. I run my late model engines at 50:1 regualr service with no problems. Good luck with your project, you deserve it. The luck that is.

 

[novacane]

Re: causes of engine failure

bump up the heat range one knotch on the plugs if mostly at low rpms run the 32-1 mix should run no problem <br />but hey you get a good one or a bad one never know

 

[seahorse5]

Re: causes of engine failure

Rolmops,<br /><br />Outboard companies went to 50:1 fuelil mix 38 years ago! If it was a bad thing, wouldn't there be piles and piles of blown motors all over the place?

 

[crab bait]

Re: causes of engine failure

wasn't not to long ago ,, yamaha's were 100 : 1 mix ??? so i heard .. rumor ??

 

[russthemuss]

Re: causes of engine failure

Hi Muskiedays,<br />I run skis and boats commercialy and i am definately ripping off the oil injection and running the premix.Oil line breaks off-buy a new engine,(twice)I dont care about the performance i just need it to last!! Im even going to try the 32:1 as suggested to give the internals a fighting chance.(well maybe 40:1)The plastic clips and bits they use nowdays are fine when NEW but give them a few years and a few repairs and their crap.

 

[Lark40]

Re: causes of engine failure

I think it also depends on the grade of oil.<br /> <br />In my 1960 Lark, which recommended straight 30 weight oil, I use any big oil company outboard product at 24:1. In my 1977 Mercury 1500 inline six, I always used Mercury QuickSilver (super expensive)at 50:1. <br /><br />Never any problems, even the several times I noticed that those engines had clogged water intakes or failed water pumps after God knows how long of idling without water.<br /><br />The lesson learned is to never cut corners on the recommended oil. And if anything, to go better than recommended.