Merc 300 pro XS v8 plastic parts?

[madmatic]

Hey guys, has any one else looked at the valve train of the new Merc v8's? It looks like there are two large plastic chain guides/tensioners for the main timing chain and two smaller plastic guides/tensioners for the outer two cam shafts. I ride Harley's and know for a fact that plastic chain tensioners and guides go out (that's what keeps the primary chain tight on them) so how is Merc still advertising a maintenance free valve train?

[powerabout]

probably got oil pressure on the back of them, very common in cars

[Davidlake]

Porsche has done that since the '60's.

[AZMIDLYF]

Common automotive use.

[madmatic]

I'm more concerned with the life of those plastic shoes rather than the tension mechanism. I change my tensioners on the HD just about every 40k miles. At 65 mph and 2500rpm that would be 6-700 hours on the outboard. I imagine that these shoes will have to keep more tension on the chain than my HD since the chain is horizontal rather than vertical, if it gets loose it will fall off. Are there any other outboards using tensioners like this? Yamaha, zuke or tohatsu? I wish Merc put that chain on the top of the power head just for price of mind.

[XstreamVking]

You replace the compressor on an opti at 800 hrs as a reg maint. procedure. Very simple repair on it. It will be the same with the 4s valve train parts. All the new car/truck motors have the same set-up and have to be serviced sooner or later. It seems easier to swap out a compressor than to break into the crank case. I have done this chain repair on a 3.7 v-6 in my sons f-150. He got nearly 200k miles before it needed repair. No such thing as maint free. They just mean no valve adj. needed.

[Bruce2]

I changed all the timing chain guides on my 2002 Ford Ranger 4.0 liter at 235,000 miles and there really wasn't anything wrong with the guides. Proper use of recommended oil and filter and oil changes at proper intervals is the key to there success.

[allaction]

Mercury >Harley Davidson

[Euroski]

VW been using them for years, but the issue was chains would stretch and tensioners would fail. Especially on the 2.0L TSI and repair was with bent valve, etc $3500 lighter wallet. Most never made it to 100,000 miles!

[syclone01]

Been used in automotive world for decades. I wonder how much cooler that new Merc will run than an air cooled harley idling in traffic?

[madmatic]

I'm just using my Harley's as a reference seeing how ive had more of them in my hands than cars, audi and jag had notorious problems with them and it seems like there a some zukes with broken chains guides. Remember in cars and bikes after the edges of the chain make a groove the rollers glide over it. Not so much when the chain is on its side. Not trying to bash Merc I'm just trying to see if this is something to prep for, is it the same set up as the verado? I haven't herd of them having issues. Here's a picture of a zuke that lost its timing chain tensioner. Would be nice if the assembly was on the top of the power head, I think Yamaha does that and uses belts but I may be wrong.

[Motv18]

Teflon, it just looks like plastic. Pretty stout stuff.

But it will cut easy as stated.

[XstreamVking]

The guides usually have very little wear. But the chains stretch further than the auto tension system is designed to compensate for. Merc is pretty smart and may have engineered for this. Every system has it's own problems. My way of thinking is, the opti's are still quite simple in their design compared to all these moving parts.

[johnmiffco]

comparing the harley chain set up to these new technology engines is apples to oranges
as stated automotive industry and other motorcycle brands have used them forever
I build lots of drag motorcycle motors,,,,
and same dual cam 4 valve set up as this new 300
never wear the guides on properly built and adjusted chains
and these drag motors on nitrous are turning 14,000rpms over the 6,400 of this motor
the Harley motor is the most vibrating ,,,,off beat loping motorcycle motor out there
and people liked that sound and Harley made 000000000s $ from it
downfall is all that offbeat vibration plays a toll on the internal components
the hard loping is making timing chain jump around thus wearing any tensioner against it
other manufacturers motors are smooth running on all other v twins,,,
not downing the Harley just way its built to give the Harley sound

[madmatic]

This is all great news to hear. As soon as I get my 300xs in November... Yeah its taking that long I will keep everyone updated with oil analysis, compression readings and some dyno pulls.