2007 496 ho 42 hours hopefully not serious

[nasdaqsam]

I just picked this boat up. There is a good amount of soot around the back of the boat especially after running with the exhaust in open mode. I have only put an hour on it since purchase. I took it out tonight and it developed a knock. It sounds like its in the upper part of the motor. Not sure if its an exhaust leak or maybe a valve or blown motor. It runs fine no loss of power etc.

I know this is impossible to diagnose with out hearing it but any ideas?

 

[flipbro]

The black soot is a sign its running rich. The knock your write hard to diagnose without hearing.

 

[nasdaqsam]

I have a guy looking at it tomorrow but tonight of course I'm in a panic tonight waiting for the diagnosis. As I bought this one to replace my old boat that blow the OB this spring but she was older and had a lot more hours. I really hope this is just an exhaust leak.

 

[Fun Times]

I took it out tonight and it developed a knock.

Is the knock at idle or under load? Check your spark plugs when you get a chance. If you're with the guy when he runs it, maybe try posting a video of the sound.

Good luck.

 

[nasdaqsam]

Thanks for the replys. The mechanic took a look at it this morning. It is an exhaust gasket. He reached around the exhaust manifold and found two bolts missing. We are going to get a magnet and and see if we can find the bolts in the bilge. So not sure if they broke off or just came out. But having this boat for less than an hours run time the question is. Is this something the former owner knew before they sold it to me? Something they cobbled up to sell? Or just something that happens?

The other question is why would an engine with so few hours have this happen in the first place.

With just 42 hours and me only having just run it it seems odd the timing.

 

[nasdaqsam]

This situation is just getting weirder and weirder. The mechanic spent some more time with it a little while ago. Used a high powered magnet and fished around the bottom of the bilge and found a few little self tapping screws, a small hose clamp and what looks to be a bolt that might be for the enclosure but no manifold bolts. He also found there were only two bolts holding the manifold in place and both were hand tight the rest were all gone and no were to be found. The other side of the motor is all perfect all the bolts there all nice and tight.

I called the former owner who also owns a marina not that it matters but he swears the motor has never been touched other than maintenance. He bought it new and sold it to me. He did some out drive work plugging the front intake holes, finishing and painting it and changed the water pump to a brass unit this was all by recommendation of Mercury but that is it. The guy was completely surprised by the issue and I am a fairly descent judge of character I really do not think he is telling a lie. I could be miss reading him.

Is it possible for something like to just happen? Does the exhaust manifold have to come off to change out the water pump possibly? Maybe they didn't put lock tight or torque them correctly? Just seems odd low hours and only one side.

 

[Fun Times]

What side of the boat while facing the bow (front) of the boat was the missing bolts? Starboard (right) or port (left)?

Also this is a stern drive boat with a Bravo drive..correct ?

 

[nasdaqsam]

Port side. Yes this is a Stern drive with the Bravo 1 X

 

[Fun Times]

The Impeller is on the lower starboard side of the engine/boat so it doesn't sound like they needed to pull the exhaust to work on the impeller unless there is 0 access.. Then in rare cases, the engine might have to be removed and sometimes engine accessories such as exhaust as well.

Try using the video of your phone and have a look at the bottom of your bilge area to see if maybe the magnet may have missed the bolts.

Hard to say if he's being truthful but sometimes you can look at the bolt heads through out the engine that have paint on them and see if the paint has been disturbed to help know if that side of the engine seems to have been disassembled or not in the past...looking for grooved/scratched socket marks.

 

[HT32BSX115]

He also found there were only two bolts holding the manifold in place and both were hand tight the rest were all gone and no were to be found.

Was the mechanic able to install new bolts where they're missing? If he was, it's possible that the original bolts were never there or were loose and fell out before the engine was installed...........it really wouldn't "hurt" anything for the bolts to be missing for 42 hrs unless the manifold literally "fell" off!

Just put in the new ones and call it "good"............

 

[nasdaqsam]

The Impeller is on the lower starboard side of the engine/boat so it doesn't sound like they needed to pull the exhaust to work on the impeller unless there is 0 access.. Then in rare cases, the engine might have to be removed and sometimes engine accessories such as exhaust as well.

Try using the video of your phone and have a look at the bottom of your bilge area to see if maybe the magnet may have missed the bolts.

Hard to say if he's being truthful but sometimes you can look at the bolt heads through out the engine that have paint on them and see if the paint has been disturbed to help know if that side of the engine seems to have been disassembled or not in the past...looking for grooved/scratched socket marks.

I will video and look for signs it has been worked on. Both great ideas thank you.

 

[nasdaqsam]

Was the mechanic able to install new bolts where they're missing? If he was, it's possible that the original bolts were never there or were loose and fell out before the engine was installed...........it really wouldn't "hurt" anything for the bolts to be missing for 42 hrs unless the manifold literally "fell" off!

Just put in the new ones and call it "good"............

He picked up new bolts they went in no problem at all. We had to order a gasket so now it just has a very slight exhaust leak. It sounds like they were missed right from the start. But I will give it a good once over tonight to see if there are marks on the bolts etc showing signs of being worked on before. It really does sound like they were just plane never there to begin with.

Thanks for the input. I have my fingers crossed.

 

[nasdaqsam]

One other thing I noticed the former owner said he never did was when the bilge kicks on I get a good amount of oil or gas on he water behind the boat. Only notice able when stopped and I know a drop looks like a tanker just dropped its load but could this have been coming from the exhaust being lose?

The former owner said that may be from the last oil change its hard to capture all the oil when taking the filter off.

 

[nasdaqsam]

Just pulled the exhaust off. About 2" off the end towards the stern completely gone. Replacing the gasket now with all new bolts this time installing the missing ones. From what i am hearing the fact that there were just two and no others there or broken off it is most likely it was a factory error. The exhaust manifolds get 2 bolts to hang the manifold while other things are being worked on it is someones job to put the other 6 in and torque them. Looks like someone was on a coffee break when this was suppose to be done.

 

[HT32BSX115]

JLooks like someone was on a coffee break when this was suppose to be done.

That never happens huh?

 

[nasdaqsam]

The exhaust gasket has been changed and the missing bolts installed. Runs great. Who would have thought after 42 hours it would be something like that. All's well that ends well.

 

[HT32BSX115]

The exhaust gasket has been changed and the missing bolts installed. Runs great. Who would have thought after 42 hours it would be something like that. All's well that ends well.

Glad it's all working good! Got any pictures of the boat? We all love pictures!

 

[nasdaqsam]

I do not have any with me but I will take some tonight and post.