Blew my 90 HP 2 stroke today :-(

[JKTrevecca]

Wide Open Throttle one second, dead the next after a rapid steady decline in RPMS. I can't tell if my issue is the result of oil/fuel starve or overheat but after getting home, I confirmed 120 PSI bottom cyl, 110 Middle cyl, and 30 top cyl. I took off the head and here is what I found. Does this look like an overheat situation to you guys or an oil starvation situation? Trying to decide whether to rebuild or get a reman powerhead. I'm not at all afraid to rebuild it myself I just don't know if it will be worth my time and effort and money compared to a reman powerhead off ebay. Any thoughts? The model # is 90ETLJ. The overheat alarm was disconnected a couple years ago because it was going off all the time as a false alarm. STUPID STUPID STUPID.

It did, after sitting in the water for a little while, start back up but ran TERRIBLY. I used the trolling motor to get home and barely had enough battery.

It does look to me like the cyl isn't scored so much as the piston melted and welded itself to the cyl wall. To me, it looks like metal on top of the cyl wall vs. a groove into the cyl material itself.

What all would be involved in this? Would I rebuild just the top hole or all 3? A reman powerhead on ebay is 1k - 1.3k based on a quick 30 second search. I haven't dug in any deeper yet.

Somebody tell me what to do!!!! Please!!!! I am determined to have this fixed before the end of the day Saturday 4/16. I have a 3 day fishing trip planned beginning Saturday. Any and all advice is welcomed. Thank You! Pix attached.

 

[racerone]

Motor needs to be torn down before decisions can be made...-----Top cylinder needs to be bored !!------------Not going to happen in a week either !

 

[tommarvin]

Get the reman for 1000.00 -1300.00 if you are in a hurry.
Or tear it apart in one day, take it to a motorcycle machine shop,ask them how many holes do they have to bore and hone, over night a Wiseco piston or two,and put it back together. If your fast this may be as fast as getting a reman. The piston # 120.00, bore hone $ 100.00, gasket set at www powerheadkit.com $90.00.

It's a tough call, IDK get the reman for $1000.00- $1300.00 ,doe's that include shipping? Do you have to send your powerhead back to them for core charge? Tax
If you can keep your power head rebuild it after the boating season ends, over the winter project, and have a spare powerhead?

 

[mphelle8vld]

I would guess no.1 was running lean because of a dirty carb, whatever decision you make with the powerhead, be sure to clean the carbs and run premix during the break-in.

It would be a good time to service the water pump and repair the warning systems.

 

[flyingscott]

1300 seems pretty cheap for a reman is it a short block. I think a week turnaround even for a reman is pushing it.

 

[JKTrevecca]

I finished the teardown yesterday. Here are the detailed photos in an online album - [FONT=&quot]https://goo.gl/photos/FCtvwgrWMd3SmqDF8 - Also - I purchased a used powerhead on ebay this morning for 1k that should get to me by Wednesday afternoon.

Here is my question - With the more detailed photos, can any of you speak to your theory regarding the cause of this failure? Oil injection failure? Just running to lean perhaps? Or overheat? Are there any signs from these pix that make the cause of the failure clear to you?

Lastly, I'd like to go ahead and repair this powerhead and re-sell it to re-coup some of my cost on the used unit. Do you guys seen anything on the bearings that would make you pause before re-using them?

Thank You![/FONT]

 

[flyingscott]

Not an oil injection failure unless the oil line to that particular cylinder broke. I am going to go with a plugged carb causing that cylinder to go lean. Rebuild your power head to new and sell the used one again.

 

[JKTrevecca]

Not an oil injection failure unless the oil line to that particular cylinder broke. I am going to go with a plugged carb causing that cylinder to go lean. Rebuild your power head to new and sell the used one again.

Thanks Flying Scott - Appreciate you taking the time to look at the pix and reply. I may do just what you suggested eventually but I went ahead and bought the used powerhead to get me fishing this weekend. After this weekend, I won't need to rush.

Sure would like to buy a new 90hp 4-stroke. They want 8600 for it at my local dealer and they say it would plug right into my 30 year old control box and wiring. Man that would be SWEET.... Too bad I've only got $1800... well... $2800 now that I bough this stupid used powerhead in my entire boat.

BTW... Here are some pix of the boat. https://goo.gl/photos/7KKadFCFsfcLS78RA I just re-built the entire interior over the winter. Of course... the motor blows within a couple months of completing that! DANG IT. I still can't get over it.

 

[JKTrevecca]

one more thing - how do you decide whether or not to replace the main bearings on the crank? visual inspection only? always replace no matter what? Thanks...

 

[robert graham]

Looks like you're pretty darn handy at fixing things and you've got a couple if fine looking young helpers there!....I've run a C90 since new in 1999 and so far, so good....sorta makes me sick to see what's going on with your motor. I'm in the habit of draining my carbs 2 or 3 times a year to try and prevent any plugged jets/ lean mixture issues....Appreciate all your good photos and good luck with your power head....keep us posted!....

 

[99yam40]

do you see any discoloration or other problems to the bearings or other surfaces?
Hard to tell looking at the pics

looks to me it was temp that melted that piston.
lean on fuel will usually cause high temps and melt piston at the exhaust port(hottest point)

 

[JKTrevecca]

Used forehead will be here tomorrow. I took apart and cleaned all 3 carbs tonight. Didn't see anything suspicious in them. I ran wire through all of the holes removed the idle and high speed jets and verified the needle valves looked good and worked properly without sticking.

I run 87 octane fuel and wal mart oil..... I know I know..... anyway... I noticed whiledriving home from work tonight that my truck was pinging under load. I wonder if I got sick me bad gas in the boat that causes pre ignition and detonation? Everyone I've had look at the motor has said it was running too lean. I will start running higher octane and see if that helps.

Quick question for you more seasoned pros... when removing the powerhead two bolts broke off in the bottom of the block. The problem is.... I can't get the remains out of the mid section to get it cleaned up and ready for my used powerhead to go on tomorrow! I started to drill email out and broke a drill bit!x!#x. Any suggestions? There are no threads in the part the two bolts are stuck in so I don't understand why they won't just come out but I am scared to hammer them too hard and brake the aluminum mid section.... ideas?

Lastly... do I need to apply any sealant to the new powerhead gasket when installing the powerhead?

Thx all!

 

[JKTrevecca]

Auto correct makes me look dumber than I am....

 

[99yam40]

Check with a local machine shop, they have a way of burning out the broken drill and taps people break off in holes, without hurting the stuff around them

 

[JKTrevecca]

Finally got the two broken bolts out. just needed a bigger hammer. It was weird, The heads were already snapped off and the threaded part was already out and into a "threadless" part. They were just siezed in there and with a more convincing hammer they popped out.

I have my used outboard 100% installed. I also cleaned the carbs and put a water pump kit with new housing in just to be 100% sure I'm not missing anything. i'm about to go start it up but in transferring all of my parts from the bad powerhead to the new, I can tell the linkages are going to need to be adjusted. I didn't change anything but the cam that rolls against the carb linkage won't go all the way to WOT now.

And... I want to be 100% sure the timing is set properly and not too far advanced so as to cause pre-ignition and BOOM again.

Would any of you be so kind as to tell me the procedure for setting the timing on this engine? I'm trying to avoid taking it to someone and I don't have time to buy the manual and get it here before I need to be fishing. Any help is muchos appreciated. Thanks

 

[LSU]

JK, you've got talent that I envy. Nice looking rebuild.

 

[JKTrevecca]

Thank you for the kind comment sir. To update this thread on the motor... I was able to fish the weekend after the blow up which was about 1 year ago. I was testing the boat/motor at 1am the night before my brother in law was to arrive for our fishing fun. The used powerhead ended up working out great... for about 3 months. Then the exact same thing happened again! This time to the bottom cyl. If I had taken photos they would have looked exactly like the ones in this thread, only the bottom hole was the culprit.

I still had the first blown motor so I figured I'd try a redneck solution. I removed only the bottom/bad piston, honed the metal transfer off the cyl walls, stuck one of the two good pistons from engine # 1 into the bottom hole with the old rings and everything. Spent $20 on some gasket maker, put the two halves of the case back together, re-installed the powerhead, checked compression (even across all 3 holes which I couldn't believe!), removed the oil injection bull crap, and have been running strong ever since then. I premix my fuel at 50:1. I have MUCH more blue smoke now than when I was running the injection system so after all is said and done, my theory is that the oil injection was the cause of both failures.

Failure # 1 cost me $1000
Failure # 2 cost me $20

I sure wish I had just rebuilt it myself the first time!

Cheers.