1984 5.7L 260HP timing chain question

[tfret]

I know I have between 6 and 7 degrees of slack in my timing chain. And I suspect this is the cause of lower than normal engine vacuum and WOT. I'm undecided but considering replacing the chain. Looking at new ones I see they are around $100 or more just for the chain. Looking at the chain for a comparable 5.7L truck engine of same year they're around $20. So I can't help but wonder if the specifications are special for the marine application? Don't misinterpret my question, I'm not looking to skimp on anything, just wondering what the difference is. I know of many good boats out there running swapped out truck engines. Thanks!

 

[achris]

Marine tax.... Buy the chain from a local car parts shop....

 

[Scott Danforth]

Mercruiser bought the motor from GM with the timing chain already installed. the timing chain didnt know where it was going to be installed (Truck motor, industrial motor, boat motor, ect.)

Melling makes the chain, they mark it up when they sell it to GM. GM then packages the chain in a box and sells it to Mercruiser with a markup. Mercruiser re-packages the chain in a Mercruiser box and further marks it up

as Achris stated, cut out the middle men and buy from your local FLAPS. make sure to get a complete set (Chain and gears)

 

[tfret]

Well honestly I was already thinking that. I mean it’s a mechanical part. I totally get it with the electrical components. But it’s a chain. I just wanted to be sure before I did something foolish. Thanks gentlemen.

 

[porscheguy]

Change the timing gears as well. It doesn’t add much time or cost to the job. Many timing chains at the parts store are sold as a kit with gears anyway.

 

[tfret]

Yeah looks like i can get the entire timing set for 50 bucks or less. Next BIG questions; can it be changed in the boat (without removing the oil pan)?? REALLY hoping the answer is yes. Access to the front of the engine is easy with the rear bench seat removed. I've never changed one before but not afraid to tackle it. I just don't want to pull the engine to do it.

 

[achris]

Bad idea to try to change it without removing the sump. The chances of messing up the gaskets are very high. Not worth the risk.

Btw, gears intermesh, the bits connected by chains are called sprockets...

Chris.....

 

[wellcraft-classic210]

I have seen people clip a little metal ( as in only whats needed ) off the timing chain metal cover in the corners to avoid pulling the pan with good success -- A local taxi cab company was doing this repeatedly on some of their bus engines. They save dropping the y pipe and possible stud replacements in that case. I seem to recall them using generous silicone in the corners as well.

That said -- -- Pulling the pan is the best fix --

 

[tfret]

I have found other write ups that describe removing front pan bolts only, and loosening the remaining pan bolts, so that the front of the oil pan can be dropped somewhat. In theory it makes sense. It's one of those things where not having done it before, I won't know for sure until I'm there.

 

[Scott Danforth]

it take 45 minutes to yank the motor (assuming you have been doing all the appropriate maintenance over the years)

 

[tfret]

Yes that’s what everyone tells me ( yes maintenance is always up to date). And that would allow me to install a Y pipe and ditch the thru hull exhaust that I’m kinda done with.