fan belt/rev meter/impeller question

[wolfgal]

hi guys,

am still crewing in the med, another problem (not my keyboqrd/computer, so this might be a bit sloppy)

so we set out early as always and, first thing wrong, the rev counter was not working,

then smelled q heavy, rubber-burning smell (no visible smoke). went below, opened up eveything

while going over what we knew for a few min, engine temp alarm went off

we turned off the engine and went down to find that the fan belt had been chewed to nothings

so we wrangled another fan belt on and hobbled to the nearest port, watching the whole time to make certain we had water spitting from the exhaust (yes, the exhaust was spitting well0

our first challenge is getting the alternator back to position as we havent an L-shaped leveraging tool and accessibility is difficult

have a few questions

any idea why the revs meter gave in on us, given the info here?

any suggestions as to how we can retighten the altenator? pleqse give suggestions

is there any way of knowing if the impeller needs to be changed without opening it up and peeking?


thanks to anyone out there

wolfie

[a64pilot]

Many boats use the alternator frequency to drive the tack, so when it quits spinning, the tack reads slow or zero. Now that you know that an odd RPM is an indicator of a slipping belt maybe next time you can catch it before it self destructs.

Big screwdriver, sometimes a broom stick, maybe even a boat hook can be used to lever an alternator. Be careful to not bust a fin on the alternator of course.
When you get your boat you May want to investigate using a turnbuckle too tighten the alternator.

I prefer using a piece of wood myself to lever an alternator, less chance of damage, I keep a couple of feet of a piece of oak flooring, I use it to drill on in case the drill punches through it’s in the wood and not the boat, also to jam the prop for when it’s removed and as an alternator lever tool and other uses.

[jkishel]

A64 covered the tach/alternator issue. Not sure why you want to check the raw water impeller, but if you do, you need to remove the water pump">raw water pump cover. Be careful to not destroy the cover gasket or o-ring, or replace with new. If impeller fins are broken off, you will need to find and remove all the pieces. They usually wind up against the upstream end of the heat exchanger.

[capt jgw]

Is the raw water pump belt or gear driven? Most are gear driven and losing the belt would not effect it. It's the fresh water pump that's driven off the belt, so when the belt failed the pump stopped spinning. That's why the temp alarm went off. Also checking the water flow in the exhaust has nothing to do with the fresh water pump so that was a wasted exercise. By all means check the raw water impeller, that needs to be done periodically anyway. They are a consumable part and you should carry spares. The vanes can break off or just wear out. If you store the boat for an off season, that's a good time to check and replace things. If you're sailing all year, you should come up with a schedule for these maintenance items.

[wolfgal]

Originally Posted by a64pilot

Many boats use the alternator frequency to drive the tack, so when it quits spinning, the tack reads slow or zero. Now that you know that an odd RPM is an indicator of a slipping belt maybe next time you can catch it before it self destructs.

Big screwdriver, sometimes a broom stick, maybe even a boat hook can be used to lever an alternator. Be careful to not bust a fin on the alternator of course.
When you get your boat you May want to investigate using a turnbuckle too tighten the alternator.

I prefer using a piece of wood myself to lever an alternator, less chance of damage, I keep a couple of feet of a piece of oak flooring, I use it to drill on in case the drill punches through it’s in the wood and not the boat, also to jam the prop for when it’s removed and as an alternator lever tool and other uses.

great info here
working on it now

thanks so much

[wolfgal]

very good, got enough to move forward now

thqnks everyone

wolfie

[Secondshift]

I feel compelled to add that while,

an under tensioned belt will likely cause a belt failure and or inefficient drive,

an overly tensioned belt may likely cause a mechanical failure as well.

The listed specifications can sometimes be vague "under medium pressure..."

Destroyed a car alternator over tightening to my idea of "medium" pressure years ago. Have since bought a tension gauge gadget and err a little cautiously.

When the alternator is driven hard at high production it has more resistance at the belt. Some with upgraded alternators report slippage while at propper belt tension. Slippage can result in friction and produce a burned rubber smell.
More tension in that case is not the remedy as mentioned.
Either a larger surface belt / pulley combo or double belt /pulley combination has been recommended... or increased alternative charging....
or a lot more spare belts.

Regards

[JPA Cate]

@ wolfgal:

Hi, wolfie, I used to have a flat blade screw driver, about 18" long [~ 450 mm] that I used to pry back the alternator to tighten the belt. I also carried a 1/2" drive breaker bar because the length gave me more leverage for tight nuts. You may be strong enough to not need one, but it really made my life easier.

rev meter = tachometer



Ann

Some day, some fellow's going to be very happy to meet you: not only are you already a sailor, but you happen to own good quality tools!

[PineyWoodsPete]

Originally Posted by capt jgw

Is the raw water pump belt or gear driven? Most are gear driven and losing the belt would not effect it. It's the fresh water pump that's driven off the belt, so when the belt failed the pump stopped spinning. That's why the temp alarm went off. Also checking the water flow in the exhaust has nothing to do with the fresh water pump so that was a wasted exercise. By all means check the raw water impeller, that needs to be done periodically anyway. They are a consumable part and you should carry spares. The vanes can break off or just wear out. If you store the boat for an off season, that's a good time to check and replace things. If you're sailing all year, you should come up with a schedule for these maintenance items.

Cap'n,I believe you've got that backwards. I've had a dozen or more diesels of at least four different brands from old Yanmar 8HP to a 165HP VW TD modern common-rail design, and all have had external belt-driven raw water pumps.

[atoll]

burning up fan belts can also be a sign that the batteries are heavily discharged or not charging properly due to dead cells,insufficient distilled water in them etc
check individual battery voltage with charging sources turned off, if it is less than 12v you have a problem.

the "raw water" pump,impellor pump , salt water pump is generally gear driven on most modern marine engines these days, (older engines or marinised engines might have a belt driven pump,generally with a second fan belt alongside the primary fan belt)

the circulation pump or freshwater/engine coolant pump and alternator is generally driven by the primary fan belt on marine engines

[Wotname]

FWIW and just one more data point regarding raw water pump drives. I have had six diesel small boat engines, three were belt driven and three were shaft driven.

The belt driven ones used a seperate belt to the alternator. The shaft driven ones were all driven by the camshaft.

[Jim Cate]

Our Kubota based Nanni 43 and our previous BMW D-35 both have gear driven raw water pumps and a belt driven coolant pump.

Obviously, there are differing designs in use.

Jim

[atoll]

Originally Posted by Wotname

FWIW and just one more data point regarding raw water pump drives. I have had six diesel small boat engines, three were belt driven and three were shaft driven.

The belt driven ones used a seperate belt to the alternator. The shaft driven ones were all driven by the camshaft.

many compressed air start diesel engines had piston pumps that worked off a cam for both cooling and raw water pumps as well as the oil pump .
fan belts were run off the main flywheel to run generators,compressors and other pumps.
piston type cam pumps were also common on steam engines

[atoll]

Originally Posted by Jim Cate

Our Kubota based Nanni 43 and our previous BMW D-35 both have gear driven raw water pumps and a belt driven coolant pump.

Obviously, there are differing designs in use.

Jim

i have a 15 hp kubota,that has no freshwater cooling circulation pump at all!
it relies on convection for circulation through the heat exchanger which is saltwater cooled by a gear driven impellor pump

[Secondshift]

Perhaps a "What engine model is it? "
early on would have proven beneficial.

Our alt and raw pump are on separate belts. Raw cooled.

Could a hard driven alternator cause an overheat ?

Regards