1st post....major engine trouble, semi-rant

First, I have been a long time reader, but this is my first post. I never really have anything to add, but LOVE to read the threads on this site. So, I have been dealing with some serious engine trouble and thought I would write a post for an FYI.

I have an '05 Centurion Lightning C4 with a Mercury 330hp Scorpion. I love this boat and would not trade it for anything...HOWEVER! Back in March, I pulled the boat out of the garage and took it for it's first ride of the season. Started up fine, ran good most of the day, but towards the end of the day I developed a small misfire in the engine. Put it on the railer and went home. The next day, I decided to investigate...started pulling spark plugs and found cyl#2 and cyl#4 plugs were completely wasted. As in, the electrodes were completely eaten away. I thought hmm...that's odd, kinda looks like detonation, but the knock sensor should have stopped that! Put a new set of plugs and called it a day. Next outing boat ran good till mid day....same type of misfire. Pulled a couple plugs on the spot only to find no problem. Went home and replaced the cap and rotor and spark plug wires. Next day, ran good...for a while, then same misfire but now seems worse. Pulled plugs, but no problem??? Put plugs back in and decided to call it a day but it ran fine so we kept going. Fast forward...mid April took it out again and this time it had a misfire right at start up but quickly went away so we partied all day without a problem. Next day, same thing...misfire at startup but this time it did not go away and now the engine is popping at anything above 3500 rpm. After getting home, pulled plugs and got water out of #2 cylinder. DOH!! Blown headgasket Or so I thought! Got on the phone with Centurion dealer...hmm, no warranty because it is '05 and the 2 year warranty did not go into effect until '06 model year. CRAP! So I decided to fix headgasket myself since I am an auto tech by trade. Well, after removing heads, I find no blown headgasket...only a damaged intake gasket allowing water to trickle over to #2cyl. After very close inspection, it became apparent that the #2 and #4 intake valves were tuliped and sucked into the seats. Took heads to machine shop and discovered ALL 8 intake valves were tuliped, and all 8 exhaust valves were in the begining stages of doing the same thing. My machinist insists that it was due to detonation and recommended I run premium fuel from here on out. He also mentioned that during the boating season he actually does quite a few of these cylinder heads (GEN X Vortec heads) and we all have a common denominator...cheap gas! He said everyone who has brought in these heads has admited to using the 87 octane cheap stuff. Personally, I am dissappointed Centurion, nor Mercury stated anywhere (that I remember) that I need to run premium fuel. Had I read that somewhere, I could have saved myself $800! So...after my very long winded first post, I just wanted to get accross to anyone with a Vortec GM 5.7L engine, do yourself a favor and run premium fuel if you don't already. Very expensive lesson learned for me to save a few bucks on each outing.

P.S., I just put the heads on last night and will be finishing up reassembly tomorrow. The heads are now equipped with one piece stainless steel valves, a competition 5 angle valve job (just because I can) and quality headgaskets as compared to the cheap graphite gaskets Mercury used. Thanks for listening to my rant....

(Message edited by lightningstrikes on May 18, 2007)

Sorry to hear about your problem!

I am curious where you running gas from last year?


Let us know how your the Scorpion performs after the upgrades

I have been running that engine in several different Centurions since 2000. I have always used regular gas with no problems. I will check with my dealer but I don't think of all the Centurions and Bryants with that engine that they have had that kind of problem.

It is possible that you just got some bad gas.

Fyi Mercury calls for 87 octane
http://www.black-scorpion.com/downloads/BlackScorpion_spec.pdf

(Message edited by krbaugh on May 18, 2007)

(Message edited by krbaugh on May 18, 2007)

You know...I am a kinda embarresed to say being a tech and all lol. As a matter of fact I did run gas from last year. Last September to be exact. Did not really think about that. I had about a half a tank when I went out for the first time in March so I topped off. Hmm....interesting.

Did the gas have stabil in it? I'm good with motors, but was just wondering

just because I can... I like this guy...

I always try to run my boat to about 1/8-1/16 of a tank at the end of the season and stabil that fuel. That way at the beginning of the season I can full fill with fresh gas.

I have an 05 Nautique with a PCM 330(Vortec), and I've been wondering the same thing. My manual says 87 is ok, but the dealer recommended 89 plus. You have me all worried now....

I put over 700hrs on my last, and have 200 on this one, and the only time I ran over 87 is when I HAD to fill up at a marina and thats all they carried. I wouldn't worry about it. Most of the blocks in our boats are the same systems as in 1/2 Ton Trucks.

A few weeks ago I had a little miss in my boat as well. When I would open it all the way up it would miss. I dont open it up all the way to often so I think it was a combination of bad gas and needing to be opened up to burn all the crap out of it. So at the end of the day I opened it up all the way and burned all the garbage out and now its running fine. I always put at least 89 in my boat but sometimes if I know I have a half tank of 89 or better Ill fill it the rest of the way with 87.

Welcome to the world of owning a Mercury!!! Mercury may want you to run 89 in that motor but not GM. Sorry about your mishap. To bad that Centurion won't run Indmar. Easier to work on, better warranty, and easier to service it yourself.

The trouble is the new summer gas has only a 60 day self life. They are going to make us start running additives like diesle motors. The old saying of filling tank for winter is wrong now. They are telling everyone to get tanks as low as possiable and to run stabil thru for winter. The new gas has more alchol in it so it absorbs more water.

Whoa, I just read my post. I meant, I'm *not* good with motors!!!!

What a moron I am.

5.7 Vortec in boat or truck is basically same however completly different load factors especially in a loaded down wakeboard boat. Running premium fuel won't give better performance but will resist detonation better.

Centurion does have PCM as an option from the east coast Plant but I have never had a problem with my Mercs so I saw no reason to pay more for a PCM

I sent a E-Mail to PCM just the other day on the octane issue here is what i got back...

The tag on the engine is incorrect, all PCM engines are calibrated to run on 87 octane gasoline.

Debra Southerland

Pleasurecraft Engine Group

Ph: 803-345-1337 ext 107

Fax 800-321-3797

Should my 2000 GT40 be run with 89 octane gas as stated on the engine or is 87 preferred?



Thanks

FYI every location(state) has different gas. Some better than others.

I run 87 without any issue. But also know that 93 would be better.

were you using arco gas. I have heard that can cause problems.

I always use ARCO...it is a few blocks from home, located on a convenient corner, and the cheapest price around. I have been debating this for a long time....I do not see what the difference is with ARCO over any other gasoline other than some certain "cleaning" additives. As far as I know, all fuel is has to have certain amounts of X-Y-Z ingredients to be sold in the US...and even more strict for California.

Ok...so the boat is back together and running! I hooked up the fake a lake and let er rip...been a while since I heard it purr so smooth. Now, I will get some sleep and head out to folsom tomorrow and see if I cant blow it up again.

Did you get rid of the old gas

HAHA...yeah about 3 tanks ago! After I finished up about an hour ago I ran the boat down to Chevron and put in some premium. I will run that from now on....even after reading Scorpions site (the link you gave me) I still will follow my machinists recommendations as I do NOT want to do this again!!

Thanks for all the comments from everyone, see you on the water!

The octane rating of a gasoline is a specific burn rate under specific condition but there are lots of other factors in gasolines. They can blend it so that it vapourizes more or less and this makes Summer or Winter gas and is one of the differences from hot climates to cold.
They have stabilizers and cleaners and metals that they may add but the base stock coming from a refinery is identical regardless of who buys it from that refinery. Where I am you may have 6 or 7 brands coming from the same refinery, but all with different packages added, or nothing added.
When you look at the octane rating the higher numbers mean they burn slower. Diesel for example burns really slow. You want the fastest burn you can without causing an explosion or having it ignite itself (unless it is diesel). That gives maximum cylinder pressure and maximum power. So run the lowest Octane you can. If the engine isn't tuned you can get carbon that can cause preignition and if your timing is advanced too much you get the same problem.
When you go to higher elevations you get lower pressures and can run slightly lower Octane. Often the gasoline at very high altitudes is blended with lower Octane rating but it should still be stated at what is tests at.
If the engine has a knock sensor it retards the timing to stop preignition should it sense it, and it senses it long before you can.
So, if you want a rule of thumb, use cheap gas. If you hear a rattle try better gas.
There are lots of other factors and lots of reasons to buy from a good station and I am perfectly happy if you ignore this. In racing fuels there can be significant power changes with different brands of gasoline that have the identical Octane number, but they are brewed in different places.

Chad, in your case higher octane seems like the wiser choice. But even a midgrade might do.

(Message edited by rallyart on May 19, 2007)

(Message edited by rallyart on May 19, 2007)