Need ideas...engine dies when in gear 5.7 with Alpa One

[aldfaa]

I have a 1996 5.7 with a Alpa one drive. I took it out and had a spirited ride running wot for maybe a minute or two. RPMs were around 4600 doing a indicated 40-45mph with a 17p prop. I noticed I was running hotter than usual- 200 so I backed off. The temp dropped back down to 160,I headed for the dock for the night but noticed the oil pressure was running alot lower than normal. Usually ran 40 underway and was down to 20

In the morning When started the oil pressure was 20 at idle and would go up to 40 at 2000rpm. I went for a ride before heading to the ramp. After warming up, the oil pressure was low again -20 psi so I started heading for the boat launch. ON the way there she started loosing power and I could not get the rpms up over 2000 in gear. In nuetral it wrapped okay. It eventually stalled the motor and died. It would restart but then die in gear. On the second attempt at getting it in gear there was a loud metallic sound then the boat wouldn't even restart.

I had fair oil pressure during this although I belive it was broken down due to the initial overheat but still had 10-20 psi. While getting towed the rest of the way in I noticed I was starting to take on a fair amount of water, I could see it running down the back of the transom near the exhaust, but couldn't get a clear view of the exact spot. Before this the bilge stayed fairly dry.

SO now it sits, and I am wondering where to start. The oil in the engine is full and looks good and clean.I was planning on pulling the lower unit and replacing the impellar and gaskets. Thinking I might of been sucking exhaust at WOT.

Where should I go from there? Engine coupler? U-joints? gimbal bearing?

 

[Bifflefan]

Re: Need ideas...engine dies when in gear 5.7 with Alpa One

The first thing is to find out what has seized up.
Pull the whole drive and see if the engine will turn over. If it will then the drive has problems. If not the start looking at the engine.
Its just a guess but if you heard a loud metal to metal noise and then started taking one water, Id think there is a drive or u-joint issue. Any way pulling the drive is a good place to start.

 

[aldfaa]

Re: Need ideas...engine dies when in gear 5.7 with Alpa One

Drained the out of the out drive. It was good and clean, no water was present. There were a few metal particals on the drainplug nothing to be concerened with.

I pulled the lower and it looks good. I can rotate the input shaft and everything feels fine no binding in either forward or reverse.

After a short fight, pulled the upper gearbox it looks good. There was water in the Bellows and the joints had some rust but turned free and no binding in unit.

Still haven;t tried restarting the engine but that is next. Oil is full and clean, I am going to check the dist. And verify that it rotates to eleminate broken gears,chain, and cam. That is on the list for tonight.

PLan on replacing the bellows(All three) gimbal bearing and the u joints. Bellows because I got a leak somewhere and the others just because I am alread in there.

Any other suggestions?

 

[Gary H NC]

Re: Need ideas...engine dies when in gear 5.7 with Alpa One

Compression and leak down test on the engine.

 

[Bondo]

Re: Need ideas...engine dies when in gear 5.7 with Alpa One

Ayuh,... Pull the sparkplugs,... If it don't turn-over,.... Pull the motor,... She sounds Beat....

 

[aldfaa]

Re: Need ideas...engine dies when in gear 5.7 with Alpa One

Well it seems that it swallowed a valve seat. No compression on cylinder. I am going to borrow a camera and scope it to verify. Last season (BEfore the boat was mine) it did the same thing. Bits of the seat ended up taken out a couple of pistons before it was all said in done. Engine was gone through, and I know a replacement head was installed.

Did the 1996 or any model 5.7L motors have a problem with dropping hardened seats?

I can't accept that it did it twice now what gives?

 

[zbnutcase]

Re: Need ideas...engine dies when in gear 5.7 with Alpa One

No. The factory seats are cut into the head, then hardened. There is no seperate seat on Chev heads. If it has 'em, they were installed by a machine shop or high volume rebuilder.

 

[aldfaa]

Re: Need ideas...engine dies when in gear 5.7 with Alpa One

Tore down the engine today and found it dropped the exhaust seat on #6. This is the same cylider that dropped a seat 2 years ago. At that time a new head was purchased (It ended up being installed on theother bank) So it was the other original head that lost seat. These are GM Heads again motor is a 96.

Is it confirmed that the original heads do not use inserted seats? I am gun shy of the current heads and looking to go aftermarket as I don't want to go through this for a third time. WOuld it be fine to run any aftermarket heads? Looking at something like the World products brand. Current pistons are speed pro h423NP

What about cam suggestions? Looking at compcams Xtreme Marine, and convert over to a roller. Any feedback/suggestions?

Engine was a 2bbl that was upgraded to a 4 bbl last season so looking to improve upon it andhave it hold together for than 1 season.