350 MPI running very rough, will not idle, loud tap

[Puma]

I found this thread about flushing engines with muffs I don't know if this pertains to you but found it interesting http://forums.iboats.com/showthread.php?t=44372

This is a very interesting article. I'm thinking that my problem was 90% root cause exhaust, but... I'm still worried about flushing, seems like a really "dangerous" procedure, especially (like my boat) when you have the flush port piped right into the engine (just downstream of the water pump). If the pressure is too high, there's no where for it to go but into the engine doing some really nasty stuff in the process.

What does everyone think? Is the "risk" of flushing worth the gains in manifold/riser/engine life? Or is the risk actually very minor and overblown by some of these articles?

 

[ardeprint]

Puma,

It seems like you have a good mechanic helping you. I agree with everthing he has suggested.

Regarding flushing your engines. I personally believe your situation was going to happen. You are due a manifold and riser swap. If anything, routine flushing, just like you did, has or would have prolonged the health of your engine.

For all who mentioned concern about the flush kits, the kits are installed into your engine as a preventive maintenance feature. Moreover they run water through the same place your raw water pump flows water. The system is designed to not allow water into your engine. Could it happen? Yes, but there would have to be a failure of a component or a total lack of intellect when using them. I try to use my flush system every time I go out. Leaving salt water in there to dry up is has much worst consequences.

 

[dicor]

I considered installing a flush kit on my B3 but after thinking about it decided against it, I figured if anything could go wrong no matter how seldom it does happen it will happen to me. Instead I installed Volvo Penta's neutra-salt system on my B3, it's a sweet system you pull into the slip at the end of the day, before shutting down and while the motor is still hot hold the Neutra-Salt switch for 45 seconds shut the motor then release the switch. From everything I've read it seems to work, we'll see.

 

[BonBini]

Puma: sounds like you at least had half your pocket out!.. Anyways about that bottom end concern; look closely at the top of pistons for witness signs of valve contact. No contact is great. Tuck your pocket in. Some contact will be ok. Heavy contact not so. Pull your pocket back out.

To check for bent rod, roll engine engine over by hand and check piston top dead center with dial indicator. A bent/twisted rod will not bring piston up as high as the rest. Keep in mind you don’t have a blue printed engine so some variations between cylinders will be normal. Doing a general comparison you will see a low piston by 0.020" ish if there is a problem. The last Perkins I checked had something liks 0.008" across 6 holes and was fine.

Another little problem on the horizon would be an egged out wrist pin bore from a moderate hit. No big deal since most automotive engines develop this just from normal use. This can only be identified by handing the rod/piston group and feeling a binding in the movement of the two. Don’t tear the engine down just for this. What you would typically hear is some piston slap when cold (a hollow mid engine reciprocating knock). As the engine warms, piston expands, this binding goes away and so does the knock.

Best of luck with all of this and keep those pockets turned out.

 

[Puma]

The pistons don't show any sign of contact. It appears that I got lucky, the problem wasn't the valves staying open, it was that the valves couldn't open because of the water (the rocker simply couldn't overcome the pressure), so the valves got beat up, but the pistons themselves don't appear to have had a contact with anything. My concern was that the overpressure that broke the valve also (before the valve gave up the ghost) bent the connecting rod.

Mechanic seems pretty confident that the damage is top end only, he suggests just putting the heads back on (after they are machined and repaired) and rechecking compression, he thinks everything will be "back to normal" then. It also sounds like my mechanic (which is 80% of the reason I'm posting) is giving reasonable/good advice and following the right course of action, so I'm inclined to believe him after hearing his diagnosis and remedies validated here.

It's amazing how incredibly strong these components are. You'd think that trying to compress a cylinder with water would just make the engine "blow up". Knock the heads off the cylinder/blow a hole in the block/etc. I was shocked when the mechanic said "the bottom end is stronger than the top, it's probably fine"; it's an incredible amount of energy with no place to go, just amazing that it can stand that kind of force. The head gasket was totally intact. In fact, from everything I can see, it appears the head is the only thing that took any hit from this at all. The mechanic said I "might" be able to just put it back together and have it work again, but suggested that I machine the heads to make sure everything seats correctly and is good and straight before it's all put back together.

Thanks for the advice, much appreciated!

Puma: sounds like you at least had half your pocket out!.. Anyways about that bottom end concern; look closely at the top of pistons for witness signs of valve contact. No contact is great. Tuck your pocket in. Some contact will be ok. Heavy contact not so. Pull your pocket back out.

To check for bent rod, roll engine engine over by hand and check piston top dead center with dial indicator. A bent/twisted rod will not bring piston up as high as the rest. Keep in mind you don’t have a blue printed engine so some variations between cylinders will be normal. Doing a general comparison you will see a low piston by 0.020" ish if there is a problem. The last Perkins I checked had something liks 0.008" across 6 holes and was fine.

Another little problem on the horizon would be an egged out wrist pin bore from a moderate hit. No big deal since most automotive engines develop this just from normal use. This can only be identified by handing the rod/piston group and feeling a binding in the movement of the two. Don’t tear the engine down just for this. What you would typically hear is some piston slap when cold (a hollow mid engine reciprocating knock). As the engine warms, piston expands, this binding goes away and so does the knock.

Best of luck with all of this and keep those pockets turned out.

 

[Puma]

Thanks, it's always good to hear that others agree with what the experts are telling me!

What exactly would "total lack of intellect" be? Running the hose full bore for 10 mins before starting the engine? Or would just 5 seconds be too much? Assume I posses this characteristic (total lack of intellect) and tell me what I should never do with my flush kit..

Puma,

It seems like you have a good mechanic helping you. I agree with everthing he has suggested.

Regarding flushing your engines. I personally believe your situation was going to happen. You are due a manifold and riser swap. If anything, routine flushing, just like you did, has or would have prolonged the health of your engine.

For all who mentioned concern about the flush kits, the kits are installed into your engine as a preventive maintenance feature. Moreover they run water through the same place your raw water pump flows water. The system is designed to not allow water into your engine. Could it happen? Yes, but there would have to be a failure of a component or a total lack of intellect when using them. I try to use my flush system every time I go out. Leaving salt water in there to dry up is has much worst consequences.

 

[Puma]

Oh, one other intersting thing.. How did the water get into the intake manifold? Think it was "blow by" when the valve gave way (and just shot some back into the manifold)? That surprised the mechanic, he didn't expect to see water there. It wasn't a lot of water, but there certainly was an obvious oil residue and a few visible small pools of oil.

 

[ardeprint]

Thanks, it's always good to hear that others agree with what the experts are telling me!

What exactly would "total lack of intellect" be? Running the hose full bore for 10 mins before starting the engine? Or would just 5 seconds be too much? Assume I posses this characteristic (total lack of intellect) and tell me what I should never do with my flush kit..

Well... I would consider lack of intellect something no member of this forum to do. But I'll enlighten the readers with some ideas.

• Modifying the water cooling system
• Plugging the outlet port while running water
• For those who use muffs. Running the flush kit with engine off and boat in an angle that would direct water back into the exhaust manifold.
• For those with inboards and the flush kit, flushing with the water intake closed and running the water for longer than 20 seconds.
• I guess running water at high pressure for an extreme period of time could couse some issues. This scenerio sounds bad, but its very unlikely. Keep in mind that your are feeding water prior to the impeller. The impeller will not allow a high level of water pressure to get by, if any, unless its damaged. Most water will just drain from the other ports in your outdrive or through the common gaps muffs have, or in my case through your water intake. In the event the water reaches the top of your risers, your boat is designed so that the risers drain water out through the exhaust at an angle which "should" direct water away from the engine and out the exhaust port. It is possible, if you are flushing on a trailer and the trailer is sitting at an angle that changes this geometry, that water could filter back into the exhaust manifold.

I hope this helps. Once again I don't think your water ingestion is a couse of you flushing your engine.

 

[Puma]

One final question. Mechanic said that he thought I might be able to reuse the manifold and spacers; just replacing the elbows (which is where it's pretty obvious the failure occured). I'm inclined to just replace everything, but wondered if anyone else has seen/done this in the past? I was under the impression that the manifolds/spacers (6" spacers on this boat) and elbows all should be replaced as a unit because if one goes, they're all about to go?

The exhaust is 2006. Never been changed, never been flushed until this year (sigh).

The PN I have for the spacers is 864908a1, is that ONE spacer, or is it one set of them? I'm hoping that's a set for the prices that I'm seeing!

Thanks!

 

[mainstream]

If it were me i would replace everything i am a firm believer is if somthing fails and the parts that go with it are of the same age id rather replace all but thats just me I dont know if you can do what your mech is telling you Im sure some one else will chime in soon good luck

 

[dicor]

If I were you I would not consider for one minute putting a 6 year old manifold that was used mainly in salt water back onto my motor. That makes no sense at all, the exhaust system is Mercruiser's weakest link, this is not the place to cut corners. I have however talked to mechanics that have reused spacers because they are easy to examine, no hidden areas. But compared to the manifold and elbow the spacer is chump change. I would go the whole nine yards, use genuine Mercruiser parts including the Mercruiser graphite gaskets and do it again in 2017 then again in 2023 then in 2028 my Kids can worry about it.

Puma check this eBay listing, it sounds like a good price if it's the one you need, be sure you get the manifold for saltwater
http://www.ebay.com/itm/OEM-MerCrui..._Accessories_Gear&hash=item1c237a0ed8&vxp=mtr

 

[Puma]

If I were you I would not consider for one minute putting a 6 year old manifold that was used mainly in salt water back onto my motor.

Well, I considered it for about 1 minute, but that's about it. Those darn spacers are expensive though, my boat uses the 6" jobbers, and they are close to 500 bucks. Can someone verify that the spacer part is indeed TWO spacers (not sold singly like the mainfolds and risers are)?

http://www.marinepowerservice.com/BoatingStore/browse_detail3.cfm?productID=41591

I tend to agree; the mechanic is giving me good advice all along so far, I just think he's worried that I'm going to die when I see the bill for all the parts. Now, I'm not happy about it, but, at the same time, I'll have much more fun on my boat knowing that this problem is not going to happen again, so, IMHO, it's worth it.

 

[dicor]

I just replaced mine last weekend with 6" spacers also and that is about what I paid for a set of 2 which includes 4 gaskets. If you plan to do it yourself be sure to make 2 locating studs it turns a big job into a cakewalk.

 

[Puma]

I just replaced mine last weekend with 6" spacers also and that is about what I paid for a set of 2 which includes 4 gaskets. If you plan to do it yourself be sure to make 2 locating studs it turns a big job into a cakewalk.

That sounds right then, they appear to be sold only as a set of 2.

What about the exhaust shutters, PN 807166a1. I was thinking of replacing them while I was in here, but it appears I need 4 of them at about 50 bucks each. Worth doing?

 

[ardeprint]

Good money spent now will save you thousands later! I'm glad you are replacing it all. I know it hurts!

 

[Puma]

Hurt it does. Going to be about 1800 for all the exhaust parts. Plus another hefty bill for the labor to rip it all apart, machine the head/valve job, and then put it all back together. Plus an oil change or 2 thrown in for good measure. Probably in the 3-4K range when I get done. <sigh>

I guess the one positive, I don't have 2 engines; if I did, this would hurt close to 2X as bad. And, the 260 Dancer is a joy to work on; there's so much room in the engine compartment, it's like a mechanic's dream.

Could be worse, that's for sure. I guess it still actually could be; if we put the heads back on and there's still bad compression in the cylinder that blew the valves out, it will be another few thousand bucks for a new short block. However, at that point, it's basically a new engine, so, if I do have to go that far, I should have years ahead of me before I have any further serious issue (although, if I do have to do a new short block, I'm going to have them do FWC at the same time; as long as I keep the boat for 5-6 years, I figure I'll make out OK on the extra cost).

Either way, I'm looking forward to having her all back together, she's a great boat that was hurt from my lack of experience and the former owner's lack of routine maintenance. Going to feel great to have her out on the water knowing that I've got many years before I have to start to worry about this problem again (hopefully >5 because I'm a nut for flushing the engine every time I use her).

You've got to wonder. Folks who buy a small boat for say, 10K or so (call it a 5-10 year old bowrider), how on earth do they afford to keep them running? Lots of small boats have the same exact engine configuration; these repairs would cost the same or more on a small bowrider. I'm assuming, of course, that people buying 10K boats are buying them because they can't afford a more expensive boat; not at all a universal truth, but often the case.

It would be like buying a Kia and getting Mercedes Benz repair bills. Not something that most Kia buyers would be able to afford, that's for sure.

Good money spent now will save you thousands later! I'm glad you are replacing it all. I know it hurts!

 

[CliffA]

You've got to wonder. Folks who buy a small boat for say, 10K or so (call it a 5-10 year old bowrider), how on earth do they afford to keep them running? Lots of small boats have the same exact engine configuration; these repairs would cost the same or more on a small bowrider. I'm assuming, of course, that people buying 10K boats are buying them because they can't afford a more expensive boat; not at all a universal truth, but often the case.

It would be like buying a Kia and getting Mercedes Benz repair bills. Not something that most Kia buyers would be able to afford, that's for sure.

i suppose i fall into the group of people you are talking about here.....at this point in my life i am not fortunate enough to be able to afford to purchase a late model mid-size cruiser....as such i decided to purchase a 12 yr old entry level cruiser (2 yrs ago at time of purchase) that was in good condition....i was able to afford the $14,000 i paid for my boat/trailer, but if i had to pay a marine mechanic to perform the service and maintenance for my boat (not to mention the numerous 'upgrades' i have done) it would put a significant strain on my finances....i knew this before i decided to purchase a boat....luckily i have the skills and tools to perform pretty much all of the work on my boat so i just have the cost of parts and materials to contend with....even if i could afford to pay a mechanic for this work i would still probably do the work myself....i enjoy getting my hands dirty and enjoy the self satisfaction that comes from being able to diagnose and repair issues as they arise....

it is also possible that some people that could easily afford to buy a larger cruiser and pay a mechanic to maintain it choose not to simply because a larger cruiser does not suit their needs or they just don't want to invest that much money in a boat....

cliff

 

[Puma]

That would be my suspicion for many; if you have the skills and the time, it would significantly reduce the costs of owning one of these engines.

And please don't take my comments as disparaging, I took the example of the bow rider because that's exactly what I sold to buy the Sea Ray, and I was in the group of people who "had an older bow rider, but could afford a bigger boat". I wanted something to get comfortable with and learn the area; and, frankly, I bought the wrong boat when I purchased my first boat. Hopefully the 260 will turn out to be the "right boat" for what me and my wife like to do (seems like it so far).

I'm just thinking back and, not that long ago, close to 2K for a new exhaust system would have been a real financial hardship and, there's nothing "special" or more expensive about mine, everyone with a SB engine needs to spend the same 2K every 5-6 years if they boat in salt. That's a big number!

i suppose i fall into the group of people you are talking about here.....at this point in my life i am not fortunate enough to be able to afford to purchase a late model mid-size cruiser....as such i decided to purchase a 12 yr old entry level cruiser (2 yrs ago at time of purchase) that was in good condition....i was able to afford the $14,000 i paid for my boat/trailer, but if i had to pay a marine mechanic to perform the service and maintenance for my boat (not to mention the numerous 'upgrades' i have done) it would put a significant strain on my finances....i knew this before i decided to purchase a boat....luckily i have the skills and tools to perform pretty much all of the work on my boat so i just have the cost of parts and materials to contend with....even if i could afford to pay a mechanic for this work i would still probably do the work myself....i enjoy getting my hands dirty and enjoy the self satisfaction that comes from being able to diagnose and repair issues as they arise....

it is also possible that some people that could easily afford to buy a larger cruiser and pay a mechanic to maintain it choose not to simply because a larger cruiser does not suit their needs or they just don't want to invest that much money in a boat....

cliff

 

[ardeprint]

Lets stop talking about working on the boats... Lets get them out on the water! Thats where the fun is!!! LOL :smt038

By the way I spend about 2.25 hours working on the boat for every hour I enjoy it. To me its worth it!

Puma good to hear you are on your way to a full recovery. Focus on preventive maintenance and she will give you years of fun. Also, you mention that your exhaust elbow was the culprit so don't be afraid to flush your engine. YOU DIDN'T DO IT! That being said, flush your motors as often af you can to prolongue the internal health. Dry salt is like a drill bit when sitting on metal.

 

[CliffA]

That would be my suspicion for many; if you have the skills and the time, it would significantly reduce the costs of owning one of these engines.

And please don't take my comments as disparaging, I took the example of the bow rider because that's exactly what I sold to buy the Sea Ray, and I was in the group of people who "had an older bow rider, but could afford a bigger boat". I wanted something to get comfortable with and learn the area; and, frankly, I bought the wrong boat when I purchased my first boat. Hopefully the 260 will turn out to be the "right boat" for what me and my wife like to do (seems like it so far).

I'm just thinking back and, not that long ago, close to 2K for a new exhaust system would have been a real financial hardship and, there's nothing "special" or more expensive about mine, everyone with a SB engine needs to spend the same 2K every 5-6 years if they boat in salt. That's a big number!

enjoy your boat...i know that we enjoy ours....i will admitt to having a 'slight' case of 'big boat envy'....that is why i have made the 'numerous upgrades' mentioned before....now our small cruiser has many features of the larger boats and suites our current needs nicely...i am relatively certain that we will upsize to something around 30 ft in a few years, especially as we get closer to retirement which is about 8-9 yrs away....but it will be an older model that has been well maintained....

cliff