Is my motor blown...your thoughts please?

FishFarmer

Cadet
Joined
Jul 21, 2013
Messages
15
Hi everybody. Glad to finally become part of the family. (sorry for the long first post)

Made a trip over to Catalina, (26 miles) the boat ran good all the way there, seemed to use a lot of fuel though. While sitting at idle the motor suddenly starting making a slight knocking type sound; I ran the boat for about 5 more miles, it felt like the boat had lost some power. I shut the boat down and restarted it several times without issue, fires right up just as it always had, it idled fine while making the same knock. I was concerned and didn’t want to potentially damage anything further so we anchored the boat and used our kayaks for our three days there. I was pretty well convinced I had something serious such as a piston or cylinder head issue and didn’t want to run the boat fearing I’d cause further damage and or damage to the bottom end / crank...etc. I considered calling for a V.A. tow from the island when we were ready to head home. Anyway, after much consideration and confirming my electronics and radios were all working properly we decided to run the boat back across the channel at first light (26 miles). The boat seemed to run fine while still making the slight knock and seeming to have less power. We got to 3 miles outside the harbor when the boat lost almost all power and the knock got much worse. I decided to shut the boat down and make the call to V.A. for the tow.
The motor is not seized; it still starts and idles while making the loud knock. I got it home, did a compression check; the #5 cylinder (bottom on starboard side) has zero compression while the other five cylinders show between 90-96psi. The #5 plug shows a little more carbon than the others but not too bad. Looking down into the #5 cylinder through the head I cannot see any damage to the top of the piston and I can’t really see the cylinder walls. I’m now debating on whether or not I’ll pull the head to inspect further or take it in to a shop. I may be able to identify the damage but that’s only half the battle as I’d then need to troubleshoot and find the cause which is probably beyond my mechanical skills.
I’m sure no one can diagnose it through this post, I’m just curious to hear some opinions as to what you guys think as I begin to prepare my mind to accept the dollar figure that I’ll hear for the repair after I take it in for complete diagnostics. Could I simply have a blown head gasket that got worse as I ran the boat? If the block is damaged is it typically more cost effective to buy a remanufactured powerhead complete with top and bottom end or have mine rebuilt? Is there a supplier of remanufactured powerheads that you would recommend?

p.s.- The impeller seems to be fine as the motor is still turning over water, I was running 91 octane and never ran the boat out of oil. This is a 1997 2-stroke 150hp Evinrude with about 600 hours.
 

HenryB

Petty Officer 1st Class
Joined
Dec 8, 2012
Messages
244
Re: Is my motor blown...your thoughts please?

I?d waste no time pulling the head for nothing more than making sure that no seawater entered the cylinder. It will give you a chance to check out the cylinder and head condition. Remove the spark plugs spin the flywheel by hand and give the cylinder a good spray of some sort of oil to make sure the rings do not seize from any saltwater corrosion. It might just be a blown gasket and nothing more.

The 91 octane sounds a little much. My 1998 140 has been on regular and Walmart oil since new. About every three or four years I remove both heads for inspection. The first time if noticed where the head gasket surface was beginning to show grooves where water was noodling its way into the cylinder and I had both heads machined for fairly short money. Since then everything has gone swell with very little cylinder wear. Give us a buzz if anything shows up.
 
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F_R

Supreme Mariner
Joined
Jul 7, 2006
Messages
28,226
Re: Is my motor blown...your thoughts please?

FishFarmer, You or somebody has to at least pull the head to see what happened. But from your tale of woe, it seems a pretty sure bet it is "blown". Not an easy fix, by any means. You were wise not to continue running it at first, but then you changed your mind. Oh well, look at the bright side, maybe the damage was already done. Now the question is how much damage?
 

boobie

Supreme Mariner
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Nov 5, 2009
Messages
20,826
Re: Is my motor blown...your thoughts please?

As said above, pull the head as you won't know anything until you do.
 

FishFarmer

Cadet
Joined
Jul 21, 2013
Messages
15
Re: Is my motor blown...your thoughts please?

Thanks for the advice guys. I know I need to pull the head and I probably will after this rainy weather passes through later in the week.
All theory I know but with the way the problem began and got worse and with the way it still starts and runs doesn't it sound more like a head gasket than a piston, rod or cylinder problem? If I burnt the rings, broke a rod or piston or lost a bearing wouldn't it lock up?
 

HenryB

Petty Officer 1st Class
Joined
Dec 8, 2012
Messages
244
Re: Is my motor blown...your thoughts please?

If the gasket has blown you have saltwater in the cylinder. You really do not want a rusty mess when you eventually pull the head.
 

boobie

Supreme Mariner
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Nov 5, 2009
Messages
20,826
Re: Is my motor blown...your thoughts please?

By the way, this mtr doesn't have head gaskets, just O-Rings.
 

FishFarmer

Cadet
Joined
Jul 21, 2013
Messages
15
Re: Is my motor blown...your thoughts please?

If the gasket has blown you have saltwater in the cylinder. You really do not want a rusty mess when you eventually pull the head.

I just pulled the plug from the #5 cylinder and sprayed pb blaster to help stop any potential corrosion from building while I wait to pull the head...thanks Henry!

Can anyone answer the questions in my last post below?

Thanks for the advice guys. I know I need to pull the head and I probably will after this rainy weather passes through later in the week.
All theory I know but with the way the problem began and got worse and with the way it still starts and runs doesn't it sound more like a head gasket than a piston, rod or cylinder problem? If I burnt the rings, broke a rod or piston or lost a bearing wouldn't it lock up?
 

boobie

Supreme Mariner
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Nov 5, 2009
Messages
20,826
Re: Is my motor blown...your thoughts please?

Pull the head and look before you run it again !!
 

FishFarmer

Cadet
Joined
Jul 21, 2013
Messages
15
Re: Is my motor blown...your thoughts please?

Pull the head and look before you run it again !!

I really don't want to run it again. But a friend of mine who is fairly good with this stuff is suggesting that before I tear the head off I hook water muffs to it and run it for a brief moment with the engine cover off to see if I can see any water or steam escaping from between the block and the cylinder head. He say's that would confirm a blown o-ring / head gasket. He seems to think there's a chance I won't be able to tell if an o-ring has failed or if the head is cracked once I have it off. Is this a bad idea?

A few more things...Generalizing here:

1.) If I pull the head and can't see any visible damage to the cylinder I will obviously assume an o-ring on the head has failed...correct? Will I be able to tell which o-ring has failed?

2.) If I can't identify the failed o-ring should I then assume I have a cracked or warped head?

3.) I need to get the #5 piston to the bottom of the stroke to be able to inspect the whole cylinder once I pull the head...rather than go through pulling all the timing gear off the top of the flywheel to be able to turn it by hand can't I just put the control in gear and turn the prop by hand...with all plugs removed of course?
 
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Randy000

Seaman
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Oct 7, 2012
Messages
57
Re: Is my motor blown...your thoughts please?

Its fine to run for a moment on the hose..a cylinder with no compression just goes alone for the ride and causes the engine to run rough. Your engine is not blown...just needs the "top" end redone worse case, not a big deal.
 

FishFarmer

Cadet
Joined
Jul 21, 2013
Messages
15
Re: Is my motor blown...your thoughts please?

Its fine to run for a moment on the hose..a cylinder with no compression just goes alone for the ride and causes the engine to run rough. Your engine is not blown...just needs the "top" end redone worse case, not a big deal.

I like the sound of that....haha
So you think the loud 'knock' is simply coming from the dead cylinder because it's not firing and not from piston slap or worse?
 

Randy000

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Oct 7, 2012
Messages
57
Re: Is my motor blown...your thoughts please?

We cant hear the sound so its unknown, but we do know hes has a cylinder with no compression. If its a connecting rod or etc is doesnt much matter just shy of knocking a hole through the block. Its going to require a tear down.
 

HenryB

Petty Officer 1st Class
Joined
Dec 8, 2012
Messages
244
Re: Is my motor blown...your thoughts please?

Don't forget to oil that cylinder well after it has been run. Fresh water is jut as bad as salt.

It doesn't take but ten minutes to pull the head we all want to hear what you find.

If water is getting into the cylinder the plug should be bright clean, no oil at all.
 
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FishFarmer

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Joined
Jul 21, 2013
Messages
15
Re: Is my motor blown...your thoughts please?

I'll definitely report back with my findings. Unfortunately it may not be until later this week.
So, I'm still a little confused on exactly how to proceed and which steps to take in which order...I know I need to pull the head but should I first run it briefly to look for escaping water and or steam? Can someone help me out with some of the questions I've asked in prior posts?
I know none of us can be sure of anything at this point...remember, I'm only looking for opinions, theories and speculation...haha

All theory I know but with the way the problem began and got worse and with the way it still starts and runs doesn't it sound more like a head gasket than a piston, rod or cylinder problem? If I burnt the rings, broke a rod or piston or lost a bearing wouldn't it lock up?

1.) If I pull the head and can't see any visible damage to the cylinder I will obviously assume an o-ring on the head has failed...correct? Will I be able to tell which o-ring has failed?

2.) If I can't identify the failed o-ring should I then assume I have a cracked or warped head?

3.) I need to get the #5 piston to the bottom of the stroke to be able to inspect the whole cylinder once I pull the head...rather than go through pulling all the timing gear off the top of the flywheel to be able to turn it by hand can't I just put the control in gear and turn the prop by hand...with all plugs removed of course?
 

jimmbo

Supreme Mariner
Joined
May 24, 2004
Messages
14,063
Re: Is my motor blown...your thoughts please?

HEAD.jpg
By the way, this mtr doesn't have head gaskets, just O-Rings.

And it has water passages between the block and the head at the top and bottom, also sealed with o-rings. Very little chance of water entering the cylinder. Pic is of a 98 ficht head
Zero compression could mean hole in piston, head gasket o-ring failure, broken piston rings. The knocking could be bearings, usually con rod, but it could be wrist pin. Don't run it anymore, it will, most likely reward you with hole in the crankcase.
 
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fromcarsToboats

Seaman Apprentice
Joined
Jul 10, 2013
Messages
46
Re: Is my motor blown...your thoughts please?

To gain the trust in it again i would tear it down, check what broke, and replace it. It could be costly and it could be simple. Unless i seen it for myself i wouldn't be able to trust it again. It could have been bad. I've seen engines come apart like a bomb went off.
 

fromcarsToboats

Seaman Apprentice
Joined
Jul 10, 2013
Messages
46
Re: Is my motor blown...your thoughts please?

I'm just saying it's best go through the whole thing or get rid of it and start over with something else.
 
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