1991 yamaha 140hp moisture issues

[GoogieMan]

G'day guy's / girls
i have a recently fully rebuilt 140hp yamaha that
over the last 3 or 4 months i have had a few problems that no one can really pin point it or point me in the right direction and the mechanic thinks its the block.

The motor sounds like it drops no4 cyl, mainly at an rpm lower than 2500rpms and the alarm will intermittently crackle on and off, With RPMS exceeding 2500 is no problems with it and runs fine without an alarm.
this how ever is intermittent, i changed the stater 2 weeks ago and it ran perfect for 2 hours then started to play up

I have changed powerpack, stater, triggers and coil packs.
No.4 plug turned milky after a few days of sitting and as did No.1 but only light moisture (there were no signs of moisture/water in any of the cyl or on the plugs after use)
the mechanic said it could be the bottom seals with water getting into it so yesterday pulled the old ones out and put new ones in and took it for a belt on the lake, ran fine didnt play up. pulled the plugs out all plugs are new and looked the same, checked this morning and theres moisture building up in No.4 plug.

I looked at the head gasket (non envasive) and noticed he used a gasket goo black tar looking stuff on the head gaskets.

i am at a loss and about to pull me hair out has anyone got a thery's on what it could be? or point me in the right direction

No.4 plug seems to be wet'er than the other's too

Thanks in advance

 

[noelm]

Re: 1991 yamaha 140hp moisture issues

In my experience (and Rodbolt may correct me here) I have found Yamaha electrics to be "almost" the last thing to suspect, especially as you are getting moisture/water on a plug, I am not too sure how an electrical issue could cause that, but you have now replaced a bucket of parts and still no closer to resolution. so, it may be time to start looking elsewhere, you say the motor was just rebuilt, how long ago?, and is there any warranty? was the rebuilder reliable? was the fault there from start up after the rebuild?

 

[GoogieMan]

Re: 1991 yamaha 140hp moisture issues

thanks for the reply, the motor was built 6months ago with a 3month warrenty witch started when the motor was put ont the boat in early december, the problem has been there probley in the first 2months, but the travel has kept both me and the mechanic away, because the same issue has been there in the warranty and hasnt been sorted it still falls on to his head well kind of, i try to pay for his fuel or offset some parts etc to travel to fix it so he dont go broke or do the runner!.

The reason why the electrics were replaced first because it was an intermittant problem that would occur one weekend and be fine for the next 2 trips then return again. its not untill recently that it has been happening nearly all the time, and sometimes when replaceing the electrics does help , like it dropped no.4 cyl whilst i was flushing the motor, i had a new coil at hand and wacked it on, immediatly it fixed the issue (well at least i thought so) the next time i went to use it, i backed her into the water started the engine and she just didnt want to fire, pulled it out of the water and put new plugs in, dropped her back in the water, fired after 6 attempts and seemed to idle fine, put her into gear and was chugging like she dropped 1 or 2 cyls, thought what the heck pulled her off the trailer and proceeded out the heads, i was trolling @ 2000rpm for about 1.5nm and all the way it was chugging, then without touching anything she started to run perfect not missing a beet, this is why im changing electrics

I have been suspecting the heads all along since i noticed moisture building up on 2 of the plug's. but he's said that it couldnt be them head gaskets are ment to be put on dry (without the use of a gasket goo!) to my knowlage.


Here is the thing, if it is playing up and if i immediatly pull the boat out of the water (or on the water) and check the plugs, 4 is oily wet (not bad just more than the others) there appers to be no water droplets on the plug. The moisture only appears a day or two after being in the water??? why

We have also taken off the Exhaust plate to check and they are still black. Apparently if theres water getting in there it will steam clean them
if theres water getting in, its only enough to effect the spark plug from fireing the fuel at low rev's with the higher revs its able to burn it off
Compression readings were 1, 125psi - 2, 125psi - 3, 125psi - 4, 120psi

 

[GoogieMan]

Re: 1991 yamaha 140hp moisture issues

just pulled the head off to find milky deposits in the head, there also appears that the pistons have been washed?? whats your takes on it.
Spoke to the mechanic and he wants to toss the block away and
photos attached

 

[GoogieMan]

Re: 1991 yamaha 140hp moisture issues

i think it maybe a head gasket problem, i emailed my mechanic these image's and still seems to think its something alittle bigger, its happening in 3 of the 4cyls no3 is dry (havent pulled that head off yet but theres moisture in cyl 1 but not 3)

 

[noelm]

Re: 1991 yamaha 140hp moisture issues

So, the guy who rebuilt it wants to toss the block away? I guess then he will refund or replace the powerhead then? I hope Rodbolt sees this and can comment on the issue, it does not sound to me as though a good rebuild has been done, more like a patch up to sell, but I could be wrong (I often am)

 

[GoogieMan]

Re: 1991 yamaha 140hp moisture issues

Hey noelm from the gong just took it to Shane Ireland, turns out warped head i dare say both are, and appears the gasket was leaking, and looks like theres been a few grabs and no 2 has a nice score in the bore didnt appear to be honed ether its only done 100 hours since it was done, so off it goes back up to him to deal with! not happy jan

he has another oversized block there he said for it, the issue has been there since the 4th time i used it so i shouldnt be liable to pay

 

[noelm]

Re: 1991 yamaha 140hp moisture issues

yep, I kind of guessed that would be the problem, but just wanted to be sure so as to not point any fingers at someone unnessarily, not too sure where you will stand as far as warranty goes, but best of luck, I had heard about your motor last week and offered some advice from a guy I know in our area, and told him about the reliability of Yamaha electrics, and also to tell you to post on here.

 

[GoogieMan]

Re: 1991 yamaha 140hp moisture issues

cheers for that, technicly its out of warranty well just, but there has been the same issue that hasnt been sorted so i believe the ball is still in his court, if it was something i have done i would pay.