Why no auto tensioner on serpintine belt systems

[walkers2rad]

I was just wondering if anyone out there had any theories on why modern marine engines that went to the serpintine system do not seem to use the automatic tensioners like cars and trucks? I dont know if all marine engines went this way, in fact I was going to ask what setup the marine power engines have but judging from a picture I saw of the 340hp it looks like they have gone back to v-belts! That kind of seems like a step backwards to me!

I have a couple different auto tensioners for chevy v-8's laying around and was thinking of trying to figure out a way to adapt one. Would apreciate any comments, theories or suggestions.
Thanks, Ray

[raythompson]

V-Belts are more reliable than serpentine belts. Autos went to serpentine to save space because of the number of components (fan, AC, PS, Alternator, etc.) and the energy to drive the components, especially the AC compressor. A marine engine generally only has the water pump, alternator, and perhaps PS.

My understanding is that tension is much more critical on a serpentine because of the load from all the components being on a single belt. There is also not as large a groove depth that can absorb belt tension that is slighty off as there is with v-belts. Combine that with the very high load of an air conditioner compressor, especially the slamming on and off from normal cycling, and you need to control the tension.

Also, with a dual belt v-belt system, such as on my Tige contains, if a v-belt breaks you will probably still be able to get home. Loose a serpentine and you are toast.

I can also carry an emergency v-belt that will get me home even if both belts fail. Emergency serpentine belts do not exist to the best of my knowledge.

[jsz]

When you say "emergency" I'm guessing you mean a spare. I carry a spare serpentine just in case. I'm sure it won't be much fun putting it on while floating in the water though (v-drive). Have any of you had to pull this off? Hard? Not too bad?

[raythompson]

No, it is not a spare belt.

What it is, is a belt that has been cut so you can snake it through any mounts that are in the way. My old boat had an engine mount that had to be removed to replace the belt. You then cut the belt to length and use special fasteners to fasten the ends of the belt together.

You cannot go fast, probably about 1200 RPM tops. But it may just get you home.

Of course my old boat only had a single belt where my Tige has two belts. The chances of both failing is very remote.

Changing a serpentine belt without tools is almost impossible, especially to get the belt back into the proper grooves. If you miss the grooves the belt will be destroyed in short order but probably longer than it takes to get you home.

I think the possibility of other failures are more prominent (such as fuel pump which I have seen happen twice, and broken starter that I have seen twice).

To carry a spare for everything possible would be, well, impossible.

[jsz]

True. But like others have said, if we have one with us, we'll probably never need it. I keep an impeller, belt, and a prop just in case the local shop doesn't have what I need when I need it.

[clinton]

changing the serp belt on the water is not too bad as I have had to do it twice now, all you need is a 5/8" socket(w/ a rachet) and a flat blade screw driver.

[clinton]

learned something new, it is better to use a 5/8" box end wrench and a 5/16" socket to replace the belt, even easier.