Mercruiser Tuliped Valve Cause?

[robnrene]

I have a 1997 Caravelle Interceptor with a 1997 Mercruiser 350 HP/IO, model #:MCM 5.7 L. I struck a sandbar while traveling at apprx 35 mph and the engine shut down. I was able to restart the boat and load it on the trailer. I took the boat out again and the engin began to surge. I lifted the engine cover and there was oil in the bilge-oil pressure gauge never dropped and no warning siren. The shop found scratches on one of the cylinders and a tuliped valve. One mechanic states that this occurred due to lack of oil but the bottom end did not burn up and the engine did not seize. Any ideas? Could this have occurred from impact w/sandbar? The prop was also spun.

 

[jlshields]

Re: Mercruiser Tuliped Valve Cause?

Usually a valve will tulip form overheating.

 

[BRIAN03]

Re: Mercruiser Tuliped Valve Cause?

You got the cylinder temp to hot. Exhaust valves will tulip with to much total timing or the engine over heated. You had to roast it. Oil has nothing to do with tulip exhaust valves. Total timing should not exceed 32 degrees on a small block chevy on pump gas. I would pull the total timing back atleast 2 degrees. You can install better exhaust valves that are less pron to tulipping. Its just money.

 

[rodbolt]

Re: Mercruiser Tuliped Valve Cause?

Hello<br /> I have replaced a lot of mushroomed intake valves in the past 3 years on the 5.7. seems over propping is a cause of overheating the valve. so far I have not seen any exhaust valves do it but several intake valves. I really cant see where running aground alone would have damaged a valve. unless you over revved ot trying to get unstuck. after working with tow-boat us in manteo for 3 years I have found its best to get a tow off the bar and not usethe motor to power off.which valve was it that mushroomed ?<br />Keep posting and let us know.

 

[robnrene]

Re: Mercruiser Tuliped Valve Cause?

It looks like the "tuliped" valve was the starboard side cylinder head and the scoring was on several of the cylinder walls concentrated on the starboard bank of cylinders. What damage should we see if there was loss of oil?

 

[dick]

Re: Mercruiser Tuliped Valve Cause?

What size prop do you run and have you always run it ?

 

[Bondo]

Re: Mercruiser Tuliped Valve Cause?

Lack of Oil causes Bearing Problems....... Crankshaft, Cam, Rockers, Lifters, Etc....<br />Not Tuliped Valves, Or Scored Cylinders.... These are Usually caused by Heat, In 1 form or another, from 1 reason or another.....

 

[BRIAN03]

Re: Mercruiser Tuliped Valve Cause?

Intake valves dont tulip. Where is all the heat. The exhaust. If by some chance you did tulip an intake valve you Melted the exhaust valve out of the engine. Flame travel, Heat, exhaust. Get rid of the heat and you wont tulip any valves.

 

[robnrene]

Re: Mercruiser Tuliped Valve Cause?

Prop was a 21 pitch that we have always used.

 

[rodbolt]

Re: Mercruiser Tuliped Valve Cause?

Hello<br /> Brian intakes do tulip. 5.7 will tulip the crap out of them if you over prop them. I repaired a bayliner with a pair of 5.7's that wiped 3 intakes. 2 one one engine and one on the other. after we were done the merc factory tech took a ride and found the boat was way over propped as well as brand new. Merc would not warrenty it. the customer had to sue some dealer in pennsylvania. it is probably the 10th 5.7 in the past 2 -3 years I have had to repair mushroomed intakes. its called swallowing a valve.<br />good luck and keep posting.<br />that is why I was asking if it was an intake or exhaust valve that was mushroomed. normally a shroomed intake will also cause that cylinder to suck water.

 

[BRIAN03]

Re: Mercruiser Tuliped Valve Cause?

A Mushroomed valve is not the same as a tulip valve. A tuliped valve is when the valve is over heated and the valve spring changes the length of the valve.It makes it longer not mushroomed. Intake valves dont Tulip all the heat is on the exhaust side the flame is going out of the cylinder head. The fuel and air charge keeps the intake side cooler than the exhaust side. Some times the people you get knowledge from dont have the real answers. Tech reps arent gospil If they admit a problem it cost there company money.

 

[jlshields]

Re: Mercruiser Tuliped Valve Cause?

Brian, excuse me but intake valves DO tulip!! In your first post in this thread you even gave some reasons for it. Why the change? Under normal circumstances the intakes do run cooler for the reason you stated BUT we are talking overheating. Intakes are not as hard as exhaust valves and can't take the heat. Detonation or pre-ignition will cause it. It can literally burn the end of a spark plug off. I've been there. And yes mushroomed is different. That's when the valve stem gets beat up till the end has a larger diameter than the rest of the stem. Caused by stuck valve, collapsed lifter, too much stem to rocker clearance, etc. <br />john

 

[Dhadley]

Re: Mercruiser Tuliped Valve Cause?

When you find a "mis-shaped" valve -- what grade fuel are they running?

 

[jlshields]

Re: Mercruiser Tuliped Valve Cause?

dHadley, in my case fuel wasn't the cause. It was a loose spark plug in one cylinder that couldn't dissapate heat and ran so hot it detonated in that cylinder only (knock sensor didn't detect it) resulting in tuliped intake valve, burned piston, scored cylinder wall. It was detonating so bad it even wallered out the wristpin bore in the piston and started knocking.<br />john

 

[Dhadley]

Re: Mercruiser Tuliped Valve Cause?

Yep -- that'll do it!<br /><br />We've seen some motors that were repeat offenders and found out the owner was using 93 octane. The guys would try to kill them on the dyno and couldnt. After they got back in the boat the valves would tulip in a very few hours. A couple of them we got to run the gas called for and one we had to recalibrate the computer for the fuel he insisted on using.<br /><br />I was just curious if anybody else had found the fuel to be a common factor.

 

[robnrene]

Re: Mercruiser Tuliped Valve Cause?

We used regular unleaded gasoline, not sure what octane that is, but it was the basic stuff. We just had a tune up prior to collision with the sandbar and all spark plugs were replaced and other regular maintenance performed. Did the impact cause the tulip and scoring?

 

[rodbolt]

Re: Mercruiser Tuliped Valve Cause?

Hello<br /> I like the mis-shape thing .I was wondering if you powered your self off the bar or got a tow? the bayliner I did was so over propped it would only turn about 3500 rpm and both engines mishapped a valve .but with no cylinder scoring. the volvo about 2 months ago misshaped one on both heads with heavy scoring and no sign of overheat or detonation. repaired the motor and it runs fine 4300 at wot. I do know of a lot of 5.7's that misshaped valves in 28-33 ft boats.<br /> Good luck and post if ya have any more info.

 

[Dhadley]

Re: Mercruiser Tuliped Valve Cause?

This follows what we have seen. Abnormally high combustion heat. It can come from wrong / old fuel, overpropping, incorrect timing, cooling restrictions, incorrect spark plugs etc. It looks like we're all seeing about the same thing.

 

[robnrene]

Re: Mercruiser Tuliped Valve Cause?

Our boat was only 21' long. When we hit the sandbar, the engine naturally revved before we realized what had happened, then we shut it down and were towed off of the sandbar.

 

[Dhadley]

Re: Mercruiser Tuliped Valve Cause?

You mentioned that the plugs were changed just prior. What plugs were installed?