Belt replacement

[Midnightsun]

Most marine engines I have seen are old school, fixed bolted adjustment. Never used a measuring tool as the old school way for a V belt was simply to push the belt with your finger to see it you have about 1/2" deflection once installed. Here is a simple way for serpentine tensioning.

https://www.youtube.com/watch?v=-f1eE9U-khU

[km1125]

It's like a torque wrench. Sometimes you NEED them an sometimes you don't. If you want to get good life out of both your belts and your bearings, then make sure the tension is set correctly. It can be off 50% one way or the other (too loose or too tight) but something is going to suffer.

I don't like that "belt twist" method because it would also vary by quite a bit depending on if it was a 4, 5 ,6 or 7 rib belt.

[Viper]

Depending on the application, it's pretty typical for older vintages to have a 2 V-belt configuration. One belt for the alternator and circ pump, and one for the raw water pump if it's an inboard application. On sterndrive applications, you may have the alternator belt also driving the power steering pump or it may have its own dedicated belt, depends on the engine.

There are variations but typically in a v-belt application, you loosen the adjustment nut on the hardware driven by the belt that has an adjustment bracket on it, usually the alternator and raw water pump. This nut will be on a bracket with a curved groove in it. This is used to pull the piece of hardware away in order to stretch the belt when installing or relieve the tension on the belt when removing it. There will also be a bolt to loosen at the pivot point. A bar is typically used against the hardware for leverage to put enough tension on the belt so that there is about 1/2" deflection when you push down the middle of the belt with your finger. When you achieve that tension, tighten the adjusting nut and the pivot nut then run the engine to test.

The only challenging engine I can recall to replace a belt is the 3.0L application where there is an engine mount on the front of the engine that must be removed to get the belt off after removing it from the crank pully.

[bud37]

QR_BBPOST So I guess im asking how to get the belt off. On a car, you have the pulley that you can adjust to loosen the belt, take it off, then install the new one. Is there a pulley or flywheel that adjusts for belt removal?

Yes there should be. Take a pic and we will for sure be able to help, it is just a guess at this point.

[Ctmangrum]

Sorry it took so long, kept forgetting to take the pics. This was the best i could do without taking out the whole deck plate.

[km1125]

Ok, those are standard V belts. Looks like you have two. Probably the larger one is the crank-circulating_water_pump-alternator and the smaller one from the crank to the raw water pump. Not sure on the mercruisers, but on the Crusaders there are two bolts holding the water pump to its bracket but the bracket has slotted holes. So you loosen up the mounting screws and slide the pump to loosen or tighten the belt. Those belts do not have to be real tight either, because the pulleys are pretty large and the belt goes half way around the pulley. Typically for the larger belt, you loosen the alternator. There should be a pivot bolt for the alternator that gets loosened, then the adjustment bracket has a bolt in a slot and you can loosen that bolt and slide the alternator up and down that slot to loosen or tighten the belt.

[km1125]

Some more descriptive info on the alternator adjustment:

merc_alternator_bracket.jpeg

[Ctmangrum]

Appreciate the info.