Toasted Motor?

[tchpet2]

Hi all,

Well, I think I might have toasted my 1986 Johnson 25hp motor. We were out on the lake (farthest we could get from the ramp of course) when the motor all of the sudden seemed to over rev. I immediatly let up on the throttle and looked at the motor. It was smoking and I noticed no water out of the pee hole........ugh! I shut the motor down immediatly, but I think it was too late. The motor contined to smoke and "sizzle". It was pretty hot!

So I brought it home and ordered the water pump kit. I also ran a compression check.........both cylinders were 45psi (UGH). I also dropped the lower unit off and stuff was melted in there (plastic spacer tube). I haven't opened up the water pump housing yet (don't want to count on my memory when the new parts come in).

I also ordered the powerhead gasket set. I know the best senerio is that it is just a head gasket, but as I tear the motor apart, what else should I be looking for? How will I know if the pistons and/or rings are roached?

This is my first boat so it will all be a learning experience for me. I have ordered the manual as well.

Should I mess with the motor of just take it to a shop? If to a shop, what kind of a bill would I be looking at?

Thanks

 

[MushCreek]

Re: Toasted Motor?

45 PSI is really low. It could be the gasket (let's hope) When you take it apart, it will be obvious if the pistons/cylinders are damaged. The aluminum will gall (literally smear) onto the cylinders. I wouldn't think a motor that age would be worth bringing to a shop- you could buy a replacement for less. The same goes for puttijg a lot of money into it. If the pistons are damaged, you're looking at machine shop charges to hone the cylinders, and new pistons and rings, plus gaskets at the very least. I don't know what they get for a rebuilt powerhead these days, but it won't be cheap.

 

[kenmyfam]

Re: Toasted Motor?

Whip the head off and have a look at the cylinder bores. Let us all know from there.

 

[tchpet2]

Re: Toasted Motor?

As soon as I get the repair manual, I will pull the head. Should get it on Wednesday.

I thought about getting a replacement, but am afraid I will just be getting someone's problems.

If I put some bucks into this one, at least I will know what I have...although I had my wife with me when the moter died and am really pushing how nice a new boat would be Especially since our 1 hour trip turned int 3 hours and she is badly sun burned. So far, her only comment is...."time to find a place on the bank to fish from"

 

[HybridMX6]

Re: Toasted Motor?

If you are lucky, as stated above, you just blew the head gasket between cylinders. You don't need a manual to pull the head, it's just like 10-12 botls or so and it will come right off. That will let you know just how big of a bill this will be to fix or replace.

 

[kenmyfam]

Re: Toasted Motor?

If you are lucky, as stated above, you just blew the head gasket between cylinders. You don't need a manual to pull the head, it's just like 10-12 botls or so and it will come right off. That will let you know just how big of a bill this will be to fix or replace.

Completely agree. Check the cylinders first before going any further.

 

[tchpet2]

Re: Toasted Motor?

You guys inspired me Here are some of the pictures I took of the head and pistons. Actually, I thought everything looked pretty good, but what do I know. Hopefully the picts turned out ok. If I need to take a different picture just let me know.

 

[tchpet2]

Re: Toasted Motor?

and a few more.

Thanks for all the help and inspiration

 

[asdasc]

Re: Toasted Motor?

I think we need to see the cylinder walls. Push one piston all the way down and see what the walls look like. Then push the other all the way down and do the same.

From that camera angle we can only see the tops of the pistons. The inside of the head looks ok.

 

[asdasc]

Re: Toasted Motor?

I spoke too soon. These pics are better. It is hard to tell, but they look decent in the pics.

What did the head gasket look like?

 

[samo_ott]

Re: Toasted Motor?

It doesn't look too bad. But as mentioned, better shots of the cylinder walls would help. Did you put the head on a piece of glass to see if it's true or not? Thats the real check. Then sand it flat on the glass.

 

[tchpet2]

Re: Toasted Motor?

Here are a few more pictures. It is hard to tell from the picts, but the cylinder walls seem to look good. They have a few dark streaks, but no gouges or grooves.

The gasket looks good to me, but I don't have a new one to compare it to.

I don't have any glass to sit it on. I guess I will need to pick up a plate of glass tomorrow.

 

[Rick.]

Re: Toasted Motor?

I don't think anyone can tell you from those pictures the condition of your cylinders. If you don't see any obvious grooves,damage, scuff marks then they well may be fine. Rick.

 

[jbjennings]

Re: Toasted Motor?

I wonder if it would be worth the time to pull the bypass covers and push in on the piston rings to see if they've still got their spring, or if they've been ruined by the heat? Heck, it's a Johnson, flatten the head and put a new head gasket on and run the darned thing!
JBJ

 

[asdasc]

Re: Toasted Motor?

Heck, it's a Johnson, flatten the head and put a new head gasket on and run the darned thing!
JBJ

That is what I am thinking!

I wouldn't go buy any glass, just hold it up to a window and look for gaps around the perimeter. If there is obvious warpage of the head, then buy a piece of glass and a big sheet of emery cloth. Then get used to sanding in a figure 8 motion until it is flat again.

 

[tchpet2]

Re: Toasted Motor?

Well, I swung in and showed the head to a local outboard mechanic. He thought the head looked good and his advice was the same as both of you????put it back together and run it!?

So, that is what I am going to do He thought the heat might have made the rings stick (lowered the compression) and, if it starts up, they should release and be fine. He said the head really didn't show any signs of getting all that hot. He thought it would be just fine.

I got the water pump stuff today, but am still waiting on the plastic tube that goes above the water pump and the head gasket. Hopefully that stuff will get here tomorrow or Thursday and I will put everything back together. Then???.keeping my fingers crossed, try to start it up.

Thanks for the help. I will let you know how it turns out!

 

[ezeke]

Re: Toasted Motor?

You should replace all three of the water deflectors while you are in there (two large, one small)

 

[tchpet2]

Re: Toasted Motor?

Finally, I got the parts yesterday, put it together and took it out today. It started and ran ok The motor ran nice and cool.

Next step, the carb kit.

Thanks everyone!

 

[noelm]

Re: Toasted Motor?

I think you are being scared off by the compresion readings, they may be low ON YOUR TESTER, can you put it all together and retest with another compression gauge just in case! by the looks of your photos, the motor has not been heated up beyond tolerance! just put it all together, replace the water pump, make sure it is pumping and run it untill it drops.

 

[tchpet2]

Re: Toasted Motor?

Just got done cleaning the carb. There was some blockage on the inlet at the very top of the carb (small hose connects to it). Started it up and is started with the first crank Didn't even have to use the choke.

However, I do have a question....I probably should start a new thread, but thought one of you might know. The top idle adjustment screw did not have a valve seat (I think that is what it is called). My manual doesn't really have a real good picture of the carb I have, although it does show the outside "packing" (rubber grommet that looks kind of like a key so it won't turn when you put the screw in) and said it was the newer type. Should there be a rubber "valve seat" or not? The carb I have is very basic and wasn't really like any in my manual.

When I screw the knob all the way in, the motor dies, but when I let it out there is almost NO adjustment. It is either dead or high idle.

I think there is a part missing. The kit I had was for multiple kits, but the seat that was included did not seam like it would go in the hole. I was afraid to really push it since I wasn't sure it was the right part and if I got it crammed in the hole, there would be NO WAY I would ever get it out.

So am I missing a part?