1996 mercruiser 5.7 with thunderbolt ignition ... Top End knock Please Help

[John_S]

Re: 1996 mercruiser 5.7 with thunderbolt ignition ... Top End knock Please Help

- Bastardized engine: SR heads, but stock 2brl intake/carb, auto distributer, who knows what else? Probably means they had some major issues already, and tried a lowball fix.

- Very low oil flow to rockers. As long as there was some lash, adjusting it would not improve it. If there is an after video, didnt see it. It should be making a big mess without rocker clips.

- Wiped lobe on cam being caused by low additives in oil vs just low oil pressure/flow, I'd lean toward the latter.

- Chances that the only issue is the cam/lobe? Very low. Can you get through a season with just cam change? Maybe/Maybe Not. It's your dice.

- Can you change the cam in the boat? Not if your bench is molded in. Maybe, if it is not. Will it be easy?, no. If you took it to car mechanics and not boat mechanics, they will probably go that route.

 

[joewithaboat]

Re: 1996 mercruiser 5.7 with thunderbolt ignition ... Top End knock Please Help

Ayuh,... Sorry joe, I'm an in-house Mechanic,... I draw my salary whether I'm wrenchin' on a dumptruck, or a boat....

I will confess to asking a loaded question Lol

I already know that at a Professional Boat mechanic shop, an in and out of a Mercruiser power can run in the $800.00 range.
To add that to a cam replacement is Lazy and inconsiderate. That is of course just my opinion.

 

[joewithaboat]

Re: 1996 mercruiser 5.7 with thunderbolt ignition ... Top End knock Please Help

- Bastardized engine: SR heads, but stock 2brl intake/carb, auto distributer, who knows what else? Probably means they had some major issues already, and tried a lowball fix.

- Very low oil flow to rockers. As long as there was some lash, adjusting it would not improve it. If there is an after video, didnt see it. It should be making a big mess without rocker clips.

- Wiped lobe on cam being caused by low additives in oil vs just low oil pressure/flow, I'd lean toward the latter.

- Chances that the only issue is the cam/lobe? Very low. Can you get through a season with just cam change? Maybe/Maybe Not. It's your dice.

- Can you change the cam in the boat? Not if your bench is molded in. Maybe, if it is not. Will it be easy?, no. If you took it to car mechanics and not boat mechanics, they will probably go that route.

Some would consider Your engine bastardized because it isn't stock! S/R heads are a common mail order replacement head. Agree that the auto distributor is weird.

High mileage engines that dont have high volume/pressure oil pumps won't shoot oil from rockers. Especially if the preload is too tight.

Most rear seats are not molded in. A person that isn't too lazy to change the cam in the boat will save the o/p major amounts of money.

Agreed the overall health of this engine could be in question. Just laugh to myself when post #2 is "time to pull your engine"

 

[tpenfield]

Re: 1996 mercruiser 5.7 with thunderbolt ignition ... Top End knock Please Help

This is in "'the mechanic's" hands now, let's let Coopin inform us of the outcome

 

[John_S]

Re: 1996 mercruiser 5.7 with thunderbolt ignition ... Top End knock Please Help

Some would consider Your engine bastardized because it isn't stock! S/R heads are a common mail order replacement head. Agree that the auto distributor is weird.

Joe, come on. I know you know better about building engines. SR heads and the stock 2brl intake/carb. Who would build such an animal on purpose? My guess would be someone tried to build a performance motor and had problems. Put the original carb/intake on to look stock and sell it. If you put SR heads on ($) and not change the cam? Maybe the cam change and break-in was botched?

High mileage engines that dont have high volume/pressure oil pumps won't shoot oil from rockers. Especially if the preload is too tight.

High milage, meaning worn bearings, pump, etc, agreed., but your at the end, and the cam lobe/lifter surface has the highest friction load. Preload too tight causing no flow? Maybe if completely bottomed out, otherwise preload position should not matter. The preload spring/depth has nothing to do with the pressure to get oil to the rocker arms.

Most rear seats are not molded in. A person that isn't too lazy to change the cam in the boat will save the o/p major amounts of money.

Don't know about the Ops, but many a new boat is not designed for maintenace, let alone a cam change. The last time we discussed this, you hadn't done one in a boat yet, to appreciate the "fun". Do you really think Don and Bondo are pulling engines just to make extra $??

Agreed the overall health of this engine could be in question. Just laugh to myself when post #2 is "time to pull your engine"

See above.

 

[coopin87]

Re: 1996 mercruiser 5.7 with thunderbolt ignition ... Top End knock Please Help

Some would consider Your engine bastardized because it isn't stock! S/R heads are a common mail order replacement head. Agree that the auto distributor is weird.

High mileage engines that dont have high volume/pressure oil pumps won't shoot oil from rockers. Especially if the preload is too tight.

Most rear seats are not molded in. A person that isn't too lazy to change the cam in the boat will save the o/p major amounts of money.

Agreed the overall health of this engine could be in question. Just laugh to myself when post #2 is "time to pull your engine"

Just to clear it up. After I adjusted the valves oil was spitting everywhere while boat was idling at 700-800 rpm's. Sorry I didnt get a chance to take another video before taking it to the shop. And yes it is at an automotive shop but lead mechanic use to own a marina and has worked on boats for 10-15 years (good guy). I do think the distributor is a bit odd and maybe it was doctored up to sell but either way I have it now and just want it to be right. Rear seat is not molded in at least it dosnt look to be. seems to be bolted down from what i saw the other day. At the end of the day Im hoping for the best but planning for the worst. Its always something isnt it

 

[QC]

Re: 1996 mercruiser 5.7 with thunderbolt ignition ... Top End knock Please Help

Ya know . . . hmmmmmmm . . . I reviewed this thread because it is such a mess. Although I don't post over here much I, like joe, have a lot of experience with engines. Not marine small blocks, not small blocks, not even gassers, but that's not the point. With that noted for no apparent reason, I have learned this: there is a right way that shops and experienced mechanics note, because . . . drum roll . . . it is the right way. Assuming people are trying to rip others off is not helpful, and frankly would probably get people punched in a face to face discussion. Sooooo, even though this venue has the wonderful benefit of anonymity and only virtual faces, I think that should stop

Annnnd . . . despite being in this Modulational club with Bondo and Don, they will both quickly confirm that I have no problem arguing with either of them. My grand assessment?

Don got it right back here:

Like I said before, you posted your point of view, others should be allowed to post theirs as well without having to answer to you each time.

If you want to pursue the issue, start a new thread.

 

[joewithaboat]

Re: 1996 mercruiser 5.7 with thunderbolt ignition ... Top End knock Please Help

In this post when i have made references to the cost of pulling an engine from a boat, my intent was not to to accuse people who are boat mechanics as being dishonest and taking advantage of someone. If this is their honest diagnosis than they are not being dishonest. I am merely offering my opinion. Just because they happen to be moderators and mechanics doesn't make them correct. I asked them to offer a cost of what they were proposing merely to make the point that a quicker repair would be vastly different in cost.

If i have personally offended either of you (Don S, Bond-o) that was not my intent and I apologize... Ill try to be less offensive next time I disagree with you.

When I make repairs for myself or someone else immediate cost and net worth when finished always comes into consideration. Spending a few hundred dollars on a used engine to very likely repair it and extending its usable life, i would consider a good gamble. IMHO metal from a cam slowly going flat is very fine and no more damaging to your engine than the metal that wears from every other place...

In a SBC most all of the oil is filtered if you keep up your oil filter service. If you dont you're bypass maybe running wide open. Lol

 

[riptorn]

Re: 1996 mercruiser 5.7 with thunderbolt ignition ... Top End knock Please Help

After reading all this I think i/o boat owners have money lined pockets. LOL

 

[vndkshn]

Re: 1996 mercruiser 5.7 with thunderbolt ignition ... Top End knock Please Help

2. Not pull the motor and DIY - Replace Cam, lifters, gasket set and a few oil changes. I would say around $300 to 400 maybe cheaper if you shopped around. Now would this work and be right? Who knows, Could last 10 years or 3 min that would be the $1000 question. Like Joe has said it has been done a million times over with the small block chevy. To me i would have wayed how long am i keeping the boat and or run it till she dies and then look into a replacment. If you are useing the boat on a lake were someone could get you back to the dock with ease then i would take the time and do it myself and chance it. But that is just me. Now out on the ocean... no way would i chance it!

I'm in agreement with this, especially if OP has his eye on a particular crate engine. I'd throw a new cam and lifters in (assuming the lifters will come out through the top, which is sometimes a real problem), put a new timing chain on it, inspect and clean the push rods and rockers, and let it run. Spend a few hundred and save the real bucks for the crate motor you want.

That said, IF I was pulling the motor for whatever reason, it would either be completely replaced or completely rebuilt. IMHO, no reason to pull the motor and inspect. At that point, the cost of new gaskets, oil pump, bearings and rings (throw in cleaning up the cylinder walls) just wouldn't be enough to stop me from just doing it right. But then, you are starting to get another few to several hundred in and that could start to eat into the crate motor budget.

I've swapped out more SBC based motor cams that have flatted lobes than I can count, the last one (when I got out of the business) was in 1997, and I know the owner of that car and it is still running fine all these years (and close to another 100k miles) later.

 

[81 Checkmate]

Re: 1996 mercruiser 5.7 with thunderbolt ignition ... Top End knock Please Help

Coopin any word yet?

 

[riptorn]

Re: 1996 mercruiser 5.7 with thunderbolt ignition ... Top End knock Please Help

Coopin any word yet?

I think he is MIA!

 

[81 Checkmate]

Re: 1996 mercruiser 5.7 with thunderbolt ignition ... Top End knock Please Help

MIA!

I was realy looking forward in seeing the outcome of this thread.

Too be continued.....................

 

[riptorn]

Re: 1996 mercruiser 5.7 with thunderbolt ignition ... Top End knock Please Help

I feel sorry for the guy. He got nailed good here. Young guy just wanted a season if that out his new bought boat.

I remember back in the 70's 80's we used to run those Gm's to the ground. add a pint of STP and she would go on. lol
the good old days with the c/i.

 

[coopin87]

Re: 1996 mercruiser 5.7 with thunderbolt ignition ... Top End knock Please Help

Sorry Guys I have been crazy busy with work and other things. The shop is supposed to look at it this morning :/. Yeah it has been sitting over there for a while but I cant complain too much because they are verifying the issue for free. Anyway I will post an update as soon as I hear from them this afternoon.

 

[coopin87]

Re: 1996 mercruiser 5.7 with thunderbolt ignition ... Top End knock Please Help

OK guys. I just got word from the mechanic. Motor is out and he said cam is good. One of the lifters was shot. And i have a few burnt valves. Cost me $600 just to have him pull diagnose and put motor back in now i have to decide if I want to put new heads on it or just have a valve job done on my current heads. Any sugestions? I would really like the boat done by this weekend. :/ not sure if that is going to happen though.

 

[81 Checkmate]

Re: 1996 mercruiser 5.7 with thunderbolt ignition ... Top End knock Please Help

Glad to see you have found the problem.

NOW THIS IS JUST MY OPINION? And im sure others would disagree!

Have him pull the oil pan and check the main bearings and rod journals, mic them or plast-a-gauge the tolerances?? maybe a new oil pump?...... if all good???.

I would put a new cam and lifter set in and have the heads redone and go boating!

Hope to see this thread end with good results!

 

[coopin87]

Re: 1996 mercruiser 5.7 with thunderbolt ignition ... Top End knock Please Help

So even though he said cam is good You still think i should have a new one put in?

 

[Idlespeedonly]

Re: 1996 mercruiser 5.7 with thunderbolt ignition ... Top End knock Please Help

What part of the lifter was bad? The roller or internals?

 

[coopin87]

Re: 1996 mercruiser 5.7 with thunderbolt ignition ... Top End knock Please Help

Internal of lifter or so i am told ... i have not been by the shop to look for myself yet