Changing a SO 42 DS V Belt / alternator belt

[sailingava]

Hi all,

I am looking to change the V belt on my SO 42 DS, it has the Yanmar 4JH4AE engine. There is not sufficient adjustment on the alternator to refit a new belt due to a hose position. Is it correct that you need to remove the water pump to create the slack to change the belt? I have tentatively looked at doing this but the water pump bolts are very tight and causes the pump to rotate rather than the bolts unscrewing.  I have searched for a "service" manual (as opposed to operating manual) and can't find one anywhere.

Any advice would be greatly appreciated.

Kind regards

Warren

[Charlie-Bravo]

On some boats, if you unbolt the alternator you can gain movement to slide a new belt over the pulley , some alternators are very fiddly to unbolt, alternatively you could remove one pulley , alternator or water pump pulley, and pop the new belt on and then replace the pulley with the belt on it.

To undo the water pump pulley (if this is what you refer to) with tight bolts, here are a few approaches,
1) hit the spanner with a hammer whilst hanging on to the pump pulley as best you can … basic but often works, and a strap wrench is handy for helping hold the pump pulley, or wedge something between the pulley and belt.
2) make/find/borrow a length of bar of some sort to sit between opposite bolt heads, loosen the other two bolts with spanner, then place the bar between the ‘just loosened’ bolt heads to undo the remaining tight ones. Reverse the procedure to tighten on assembly.
Some pumps have a raised boss in the middle which makes using the bar impossible unless you can cut a bit out of the bar to sit over the boss, a handy future tool for the ships toolbox perhaps.
3) Place a ring of a combination spanner on one bolt head and a ‘stick’ in the open spanner end, place the other stick end on another bit of engine, and if everything is in a straight line the pulley can now not move ……. (is this making any sense?) ……. loosen bolts.
4) Use an impact driver, (probably the easiest)

It is good to imagine you are at sea, escaping a storm and trying to enter a tight harbour under engine, it is at this point that a belt LIKES to break ! in this event you would want to replace your belt with your spare belt quite quickly whilst below bouncing around, so once you have decided on how you will tackle the current problem, give some thought to how it could be done in less than ideal conditions, make sure everything is on board for the next time.
I had a similar issue on the 35, and have now modified the alternator swing for quick belt changes.

Perhaps there is a ‘knack’ to be learnt with your engine that someone will come along with.

Good luck
CB

[sailingava]

Whilst I will await if there is a 'knack'to changing the belt,your advice is hugely welcomed thank you.

My concern is exactly as you describe ... what if it happened at the moment I needed the engine the most?! Hence I am seeking to replace annually and work out the most efficient method.

Thanks again
Warren

[bereboot]

I once saw a mechanic putting the belt on with a tire iron.

[Charlie-Bravo]

Leavering it on can be done as you say, …. but only if it is a very light bit of leavening, it’s a bit mean to the belt,  better to re engineer things for an easy life.

Just to make things easy, I have removed the belt cover, and have no plans to re install it, it allows the belt to run cooler, I can see and feel the belt tension, and is one less thing to get in the way at belt change.

CB

[ianf]

Before I moved on to a Balmar alternator and a serpentine belt I used to change the V belt by loosening both the tension adjusting bolt and the adjusting bracket bolt which bolts the bracket to the engine block. I then put the new belt over the crankshaft pulley and the alternator pulley and dealt with the water pump pulley last by heaving the alternator over and squishing the water hose a bit and then rolling the belt onto the water pump pulley rather like you would put a bicycle chain on. 

If the belt is new and stiff it may need a bit of leverage and possibly a bit of a soak in hot water before hand.

[Mistroma]

I used to do the same as ianf but changed method when replacing with a new, stiffer belt. I just removed the water pump pulley bolts and continued with that method as it was easier. It was a little tricky loosening the 4 bolts on the pulley initially but not a big deal. I left the belt tight initially. Then I think that I used a ring spanner on one bolt to lock the pulley whilst loosening another with a socket. Combination of resistance by belt and ring spanner made it easy to undo the first bolt. I used a long screwdriver across two loosened bolts to loosen the last bolt. I always loosen the bottom pivot bolts with socket plus spanner on spacer between front and back lower pivot points. Then I remove the top adjustment bolt in the slot.

[John]

The belt can be removed or refitted by loosening the top bolt and the lower bolt on the alternator , you might need to use a flat screwdriver to help it on or off , you don't need to remove the alternator to do this .
Use a large flat screw driver under the alternator to help tightening the belt ,tighten the bolt with a ring spanner or socket set .

[sailingava]

Thanks all for the advice.  I managed to squeeze the interfering hose and use a screwdriver to lever the alternator to create as much slack as possible in the v belt. This enabled me to twist off the old belt and replace it with a new one without causing any damage. Having done so, I am reasonably confident I could do it again - when it matters at sea.  I have also left off the engine/belt cover for ease of access in the future.

Many thanks again.

Warren