alternator?

[boatman37]

have to check it out tomorrow but i'm thinking i may need a new alternator. how do you go about finding the right replacement? is there a catalog to look it up? how about the belts? i want to at least buy replacement belts to keep them onboard but if i replace the alternator then i will replace the belts at the same time. is it a matter of taking the belts to the auto parts store? the one has a marking on it which looks like it might be the part number but the other belt isn't readable. FWIW its a 1986 sea ray 250 sundancer 5.7 merc

 

[alldodge]

FWIW its a 1986 sea ray 250 sundancer 5.7 merc

Without this we would be asking what are you working on, but still need a engine serial number to verify your part numbers. Without a serial number I'll offer these
ALT belt - 57-93658Q
Water pump and Power steering - 57-37619Q

Could also take the belts to the auto parts store

 

[boatman37]

i will try to get a serial# today. i will be headed to the marina later. i will also try to find better #s on the belts. don't want to take the existing belts off to take them into a parts store unless i am replacing the alternator as i don't want to tear it apart unless i need to. the belts look pretty easy to replace so i just want to have spares onboard in case i need them.

where would i find the serial #s? on a small block chevy they are typically on a pad at the front of the cylinder head. i assume they are the same on these? or are we talking about a different serial #? maybe from mercruiser?

 

[alldodge]

Look above the starter for a plate.
https://www.perfprotech.com/blog/art...serial-numbers

 

[boatman37]

ahhhhh.....thanks! will look today

 

[UncleWillie]

...Have to check it out tomorrow but i'm thinking I may need a new alternator...

You think you May need an Alternator???

Engine OFF ... Battery Voltage = ~12.6v
Engine ON ... Battery Voltage = >13.5? = ALT Good! (>14v is Typical) .... <12.6v? = ALT or connections to it are Bad!
If Bad, Measure at Battery and Alternator, Both readings should be identical.

 

[airshot]

Before throwing money into an unkown problem, I would pull your alternator and take it to a starter/alternator rebuilder. Marine units are not cheap and not as well made as original equipment alternators. Do not use a pace like auto zone or other local auto shop....you will need to find a real re-builder that knows what they are doing and they can test it out so you know for sure.

 

[boatman37]

thanks for the info guys. i will check it tomorrow. i was down there today but got tied up with other stuff. i did take it out for a quick run. volt meter read about 12.5 but not sure how accurate that is. the end of my multi-meter broke off so made it hard to test it today. going to solder an alligator clip on and try again tomorrow. i was able to check the battery voltage after we came back in by touching the bare wire on the terminals. had about 12.7 on batt#2 (regular car battery) and 10.7 on batt#1 (new deep cell battery). this was with engine off. i ran on #1 on the short trip...maybe 30 minutes.

four guys at our marina have bought alternators from DB electric off ebay and all are working great. they cost about $60 and are marine rated 105 amp'ers. http://www.ebay.com/itm/NEW-105-Amp...ire-/140661477619?hash=item20c013d0f3&vxp=mtr

 

[alldodge]

Your 10.7V bat should be replaced if you cannot get it up after charging.

I bought one of the ALTs from DB years ago, called a one wire. All regulation is done internally. You can get a plug from them to use your current charging setup with the two wires that plug into the back.

 

[boatman37]

thanks. the 10.7V battery is new but i was running off that one while we were out so my theory is it ran down with a weak alternator. i did notice at full charge it only reads about 12.0V. a little low but thought maybe cause it was a deep cycle the actual voltage may be lower than a standard battery. i will re-check it today with the fresh charge and hopefully fixed multimeter

i checked for the serial# plate. couldn't see it with the naked eye cause of the location and room to move but got a recording with my phone but its too blurry. but i did see the #'s on the PS belt and it is 57-37619. i will be trying to get more info today and try to get the #'s off the plate.

also, talked to the PO yesterday (he bought the boat new) and he said he thinks that alternator is the original (~600 hours and 30 years old)

 

[alldodge]

Fully charged 12V battery should read 12.7V off charger and disconnected from everything

 

[boatman37]

k. both batteries read 12.7 engine off charger disconnected. engine running they read 13.6. so seems alternator is not a problem. also, got the serial# off the block. A593759. it may be A583759 but pretty sure its a 9. i did get both belt #s too. 57-37619 on the PS and 57-93658 on the ALT

 

[boatman37]

another question. just read a post about battery isolators. mine has an isolater. my plan is to run using my regular 'car' battery (#2) and when anchored i will use my marine battery (#1). does any of this matter with an isolator? i do not have an onboard charger but bought a battery tender and leave it plugged in 24x7 at the marina using shore power.

 

[alldodge]

another question. just read a post about battery isolators. mine has an isolater. my plan is to run using my regular 'car' battery (#2) and when anchored i will use my marine battery (#1). does any of this matter with an isolator? i do not have an onboard charger but bought a battery tender and leave it plugged in 24x7 at the marina using shore power.

A tender will not be able to charge up a battery, tenders are used for tending only, max 1 amp or so. Trying to use them to charge a battery will burn them out over time. Now if your tender can put out more then 3 amps it should be fine, but will take a awhile to charge a battery if it is down 76% or so

 

[boatman37]

sorry. it is a charger with 15A, 10A, and 2A tender. http://www.autozone.com/test-scan-a...5-10-2-amp-marine-battery-charger/539231_0_0/

it will charge until at capacity then maintain

 

[alldodge]

Cool then your good to go

 

[boatman37]

thanks