Major Ongoing Engine Problems - Opinions Wanted-gctid367844

[Guest]

Last year I purchased a used 2006 305 with twin 5.0L 220Hp engines that had only 71 confirmed hours in fresh water. No issues were found in the pre-purchase engine survey and because of the timeframe, I had a 100Hour service done before I took possession. At the 100 Hours mark, I started having problems first with the port engine with tuliped valves and had that repaired. Almost immediately following (two hours later) I had the same problem with the starboard engine and in addition there was scoring on some cylinders and had the long block replaced and valves.

I took the boat out for a couple of hours (only TWO HOURS since the repairs) and had a head gasket failure to the port engine. Mercury confirmed and is covering the cost of those repairs. However, during the inspection, the Marina has found scoring in one of the cylinders and I am waiting for their next steps but my guess is another long block replacement. I am being told these issues are coming from overwork of the engines since they are the lowest HP Bayliner used and they have recommended switching from a 21" prop to a smaller one (perhaps 19"). After the initial repairs, I only had 1/2 fuel and two people on board and never went over cruise rpm (~3,800) so the boat wasn't loaded down at all.

My problem with all this is I purchased a boat with little hours with all factory spec/original equipment and I am having MAJOR engine issues related to factory "configuration". Since they boat is out of warranty, I am told Mercury/Bayliner won't help out on any of this and I am looking for some sanity checks and points of view of the issues and perhaps if I should bypass the marina and try to get to Bayliner/Mercury. I am also fearful that if I fix this again, I'll just see the same problems in a few more hours and I can't afford to keep fixing these problems at these intervals.

[2850Bounty]

Did anyone do any forensic work related to mapping out ignition timing, and/or fuel metering?

I can't imagine seeing this type of damage, and then replacing parts, without first checking all aspects of anything that may have contributed to the cause.

That's like installing new front tires, due to severe wear, without checking front end alignment. rod (where is the "DUH" emoticon?)

.

[Guest]

There are plenty of 305's with twin 5.0's out there. That sounds like a BS excuse to push the blame off on someone else. There isnt much HP diff between 5.0 and 5.7 and if you ahve fuel injected 5.0 your pushing the same HP as my 5.7.

Your issues however are concerning and why its happening to both engines like that???

305's came with 5.0, 5.7, 7.4, and diesel. Most common I believe are the 5.0, 5.7 wasn't as common when I was looking for 3055's. From everything I have heard, 5.0's have plenty of power. In fact I was looking at a couple 01's with 5.0's, they had 200-500 hours on them with no issues like you have described.

[Guest]

I know the port engine was retimed after the initial problem when the valves were replaced but that was about it and the problem was chalked up to overworked engine/propping. To me the key is the minimal hours associated with the problems and what is that severe enough it could cause this without longer hours. I am not a mechanic but I am learning through forced introduction to this but with the new set of problems, the little use and barely anyone/fuel on board, overwork does not seem like the problem to me.

[Guest]

I should add they are carb and not MPI and I had the Carb rebuilt "just in case" on the port engine

[Guest]

The 5.0 TKS series carbed engines are fairly straight forward, unless someone messed with timing and/or carb mixture setting is incorrect they should not fail like that.

What was your WOT rpm when both engines worked? If both engines could reach 4600RPM, than props are correctly sized for the load.

[Guest]

My 2 cents. Seems to me marine engines that have not exceeded 3800RPM are not being "overworked". You may not have the performance you'd expect, but I question whether you ruined them by "overwork" Things I'd look for are - 1st) - was there any indication of water in the cylinders/crankcase oil?? water injestion due to exhaust/cooling parts problems could cause cylinder scoring and tuliped valves. 2nd) - overheating - did the engines run hot or at normal temp? 3rd) - considering the breakdown of 2 engines, I'd be looking at possible fuel issues.

That's where I'd start.

[Guest]

The "engine being overworked" excuse is BS- what shop told you that nonsense?

Sounds like your shop is looking at you like an ATM machine. In addition to the already mentioned concerns- scored cylinder walls don't automatically equate to a new longblock.

[Guest]

captjmh wrote:
My 2 cents. Seems to me marine engines that have not exceeded 3800RPM are not being "overworked". You may not have the performance you'd expect, but I question whether you ruined them by "overwork" Things I'd look for are - 1st) - was there any indication of water in the cylinders/crankcase oil?? water injestion due to exhaust/cooling parts problems could cause cylinder scoring and tuliped valves. 2nd) - overheating - did the engines run hot or at normal temp? 3rd) - considering the breakdown of 2 engines, I'd be looking at possible fuel issues.

That's where I'd start.

I have to agree with this. If you're confident that the prepurchase inspection was accurate. Im thinking overheating. I'd want to know how the boat was stored before you bought it. In the water, out of the water? Closed cooling or raw? Did coolant water sit in the block for long periods without running the engines? More questions than answers at this point.

[706jim]

3800 rpm in itself isn't so bad unless the engines would only top out at 3900WOT.

Bottom slime can slow you down considerably and if the boat were overpropped, it could lead to an overheating situation.

[Guest]

Sounds like a overheating issue to me either from the cooling system or engine running ie. timing or weak mixture/timing problem a lot of things need checking before blindly replacing parts and trying again..........Paul...........

[captharv]

A 2006 engine would have a thunderbolt V ignition computer. It also has a knock sensor. The sensor is merely a microphone which looks for knock.

If it hears knock, it reduces the timing until it stops. If it is a running engine the system increases the timing until it hears knock and backs it off where it just stops. If the sensor is bad or not connected, the system will advance the timing as much as 10* over base curve. This is harmful to the engine, and may burn thru a piston.

A competant mechanic should have tested the sensor(s).

Blew a head gasket just after the mechanic did a valve job? whats wrong with this picture? It just set off my bravo sierra alarm.......

[captharv]

A 2006 engine would have a thunderbolt V ignition computer. It also has a knock sensor. The sensor is merely a microphone which looks for knock.

If it hears knock, it reduces the timing until it stops. If it is a running engine the ystem increases the timing until it hears knock and backs it off where it just stops. If the sensor is bad or not connected, the system will advance the timing as much as 10* over bas curve. This is harmful to the engine, and may burn thru a piston.

A competant mechanic should have tested the sensor(s).

Blew a head gasket just after the mechanic did a valve job? whats wrong with this picture? It just set off my bravo sierra alarm.......

I think you need a second opinion.

[Chief_Alen]

Engines have a wide open throttle recommended rpm. Twice a year the first trip out and the last trip out i usually check mine.

I " guess " yours is around 4600-4800 rpm should be posted on each engine.

If your not achieving recommended wot rpm your lugging your engines.

There are many many reasons for not achieving recommended wot rpm.

Here is a list....

List of possible causes of low WOT (Wide Open Throttle) rpm.

In no particular order

Engine Won't Reach Operating RPM. Check

1. Fuel condition. Type and Octane possibly old fuel

2. Propeller pitch or diameter, damaged blades

3. Restricted fuel pickup tube or anti siphon valve Fuel System Test

4. Crankcase oil volume, high oil level can cause aerated oil and lifter collapse

5. Marine growth on hull and outdrive

6. Wrong gear ratio in outdrive

7. Restricted carburetor air intake (clogged flame arrestor)

8. Restricted exhaust system (broken exhaust shutters/flappers) in engine transom shield or drive

9. Poor cylinder compression Compression Test

10. Carburetor defective, or wrong type.

11. Fuel pump pressure and vacuum

12. Boat overloaded, improperly loaded, or improperly trimmed.

13. Engine Overheating

14. Engine timing and ignition system operation

15. Remote control cables and linkage for proper travel to open throttle plates fully.

Above copied and pasted from another website Don s is the author.

I will add one hidden water trapped in the hull. More common then people believe and generally overlooked.

[2850Bounty]

captharv wrote:
A 2006 engine would have a thunderbolt V ignition computer. It also has a knock sensor. The sensor is merely a microphone which looks for knock.

If it hears knock, it reduces the timing until it stops. If it is a running engine the ystem increases the timing until it hears knock and backs it off where it just stops. If the sensor is bad or not connected, the system will advance the timing as much as 10* over bas curve. This is harmful to the engine, and may burn thru a piston.

A competant mechanic should have tested the sensor(s).

Blew a head gasket just after the mechanic did a valve job? whats wrong with this picture? It just set off my bravo sierra alarm.......

I think you need a second opinion.

Fully agree!

Chief Alen wrote:
Engines have a wide open throttle recommended rpm. Twice a year the first trip out and the last trip out i usually check mine.

I " guess " yours is around 4600-4800 rpm should be posted on each engine.

If your not achieving recommended wot rpm your lugging your engines.

There are many many reasons for not achieving recommended wot rpm.

Here is a list....

List of possible causes of low WOT (Wide Open Throttle) rpm.

In no particular order

Engine Won't Reach Operating RPM. Check

1. Fuel condition. Type and Octane possibly old fuel

2. Propeller pitch or diameter, damaged blades

3. Restricted fuel pickup tube or anti siphon valve Fuel System Test

4. Crankcase oil volume, high oil level can cause aerated oil and lifter collapse [COLOR]"#0000FF" wrote:
....... meaning that the cam follower plunger is not effectively trapping hydraulic pressue![/COLOR]

5. Marine growth on hull and outdrive

6. Wrong gear ratio in outdrive

7. Restricted carburetor air intake (clogged flame arrestor)

8. Restricted exhaust system (broken exhaust shutters/flappers) in engine transom shield or drive

9. Poor cylinder compression Compression Test

10. Carburetor defective, or wrong type.

11. Fuel pump pressure and vacuum

12. Boat overloaded, improperly loaded, or improperly trimmed.

13. Engine Overheating

14. Engine timing and ignition system operation [COLOR]"#0000FF" wrote:
.....extremely important.[/COLOR]

15. Remote control cables and linkage for proper travel to open throttle plates fully.

Again... I agree!

This is why some form of forensic work should have been protocol as the engine was being taken apart.

These 5.0L engines are no doubt fitted with full dished pistons, of which do zero against detonation potential.

Let's assume that this damage is from ignition induced detonation and from possible over-burdening.

Once detonation begins, it becomes self perpetuating.

Cylinder temperatures increase beyond normal.

Engine block temp may appear to be normal.

Exhaust valves get too hot, begin to tulip.

Once the tulipping begins, the vavle stem raises up taller within the valve guide.

The valve stems then raise the rocker arms.

The rocker arms then set the push rod deeper into the cam follower.

The cam follower plunger begins to reach the end of it's effective travel.

If the original cam follower adjustment was favoring the bottom of the plunger travel, this certainly doesn't help matters.

Once the effective travel is exceeded, the valve can no longer fully close.

Now hot escaping exhaust gasses further destroy the valve seating ability.

Again, this would be assuming that the damage is/was from detonation.

I'm not necessarily blaming the full dished pistons.... just pointing out what may be part of this scenario.

The WOT RPM is very important.

If not capable or reaching WOT RPM, then what Chief suggested becomes a real issue.

Add to this that operating while over-burdening, self perpetuates the high cylinder temperature scenario, yada yada yada.... and so on.

I think that some steps backwards here for some form of forensic work should be taken, but this won't be easy now!

There's no sense in yet another repeat of this same thing if you do not learn what caused this in the first place.

.