Alternator selection for Mercruiser 470

[AeroNautical]

I have a 1986 Wellcraft with a Mercruiser 470. The engine already has been upgrade for the alternator, but that alternator has died and I would like suggestions for a replacement. It is a single wire alternator and I would like to make the replacement one as well for ease of installation. I have a dual battery system, a house and a start battery, with a selector switch. I have very little electrical load put on the batteries, a depth alarm, fish finder and a small stereo.
I am not sure what size the current one is because it is too faded/corroded to read, but I was thinking a 65amp would be suitable for my needs. It seems 105amp ones are more prevelant when shopping online so I may just get one of those.

Any thoughts? Thanks!

 

[Scott Danforth]

most kits are 45 or 55 amps

so either get another 45-55 amp unit (about $75) or take yours in to a starter and alternator shop and spend the $30 to have it fixed

your original stator/rectifier system was only about 10 amps.

anything over 75 amps and you need dual belts to drive it.

105 amp would be over kill, require new wiring and new pulleys

 

[AeroNautical]

Thanks for the reply. I just have a few more questions. The Delco 105Amp alternator appears to have only a single belt pulley on it. Where would the second belt go? Lastly, when you say new wiring, do you mean from the alternator to the battery or throughout the entire boat?

Thank you for the help!

 

[Scott Danforth]

because its a delco alternator with the wrong $8 pulley bolted to it. Delco does not sell the alternator with a pulley or a fan, they sell the alternator to distributors and the pulley and fan gets added at the distributor level.

if you tried to load it up to 100 amps it would smoke the belt as you can only drive a 70 amp alternator or smaller with a single belt (technically is a tad over 5hp you can drive with a single belt)

and yes, with a 105 amp alternator, all the wiring from the alternator to the battery would need to be increased to 4 gauge at a minimum, most likely 2 gauge.


not to mention, your words were that you do not have much of an electrical load.

so why are you looking larger than a 50 amp alternator?

 

[sam am I]

https://www.amazon.com/Electrical-Ad...M9ZV3BF891P5W6

Single belt pulley on 105 Amp....are STOCK!!

You can always make/wire a single wire alt if need be by using a 3 wire and jumping alt's term #2 (sense) to Batt out term...........You can more or less let term #1(field's high side/ind light) float, there's enough residual magnetization in the armature steel to kick it on. Sometimes however, if the alt has sat on the shelf for a very long time, you might have to momentarily touch term #1 to the batt.

https://www.google.com/search?q=wire...=1920&bih=1005





Your wiring only needs to be changed IF you try to draw 105 amps from it.........Meaning? If your normal loads stay more or less normal (55'ish), your wiring can stay normal even if the alt is Hoover dam, current through the wires is determined by the load, not the alt.

 

[Scott Danforth]

DB electrical are Delco knock-offs, not true delco alternators. Not a single part on the alternator from DB electrical is a Delco part.

a true Delco 10 SI is available in 37 amps, 42 amps, 55 amps, 61 amps and 63 amps. the 10 SI frame is technically too small for 105 amps as the cooling is designed for 63 amps only. pulling 100 amps from the Cloned 10SI's for any significant period of time will burn out the windings and the diode pack.

a true Delco 12 SI is available in 56 amp, 66 amp, 78 amp and the maximum 94 amp output


and a 105 amp should have dual v-belts

 

[sam am I]

LOL, okay, so aside of DB's internal quality controls or being Delco clones or not, diode explosions and rated continuous amps at given rpm's per case size and the like.......... Generally speaking, a standard single 1/2" V-belt (standard V8 engine size belt) can/will work fine and is manu accepted (as seen by the single pulley above) up to a 150 amp alt. If the belts are 3/8 or smaller, dual belts are manu recommended. However yes, dual 1/2's, serpentine, etc would work and is absolutely a safe bet, just not required.

 

[Scott Danforth]

the engineers at Delco and Cummins that I delt with for over 15 years would tend to disagree.

in either case, a 470 doesnt need anything larger than a 45 or 55 amp alternator

 

[sam am I]

wELL!!.........The engineers I work with at Balmar for 30+ yrs could beat your engineers up any day of the week!!


100/150 amps equates to about 4/5 HP........
Alt'S max output ratings 100/150 amps at somewhere around 6500 rpm....

Chart page 9 calls for a single type A, AX V-belt for anything requiring 4/5 hp @ 400 rpm's and higher..

https://www.baldor.com/mvc/DownloadCenter/Files/MS4050

2nd source.....

https://www.machinedesign.com/archiv...eritable-cinch

Verify 1/2" width for type........"A" "AX" V-belt.......

https://www.thebigbearingstore.com/a-4l-v-belts/
https://www.thebigbearingstore.com/ax-v-belts/

Double checking below link for a basic rule of thumb and second source for above assertions...... Are we in ball park for using single 1/2" v-belt at or around 12V 100/150 amps?


https://www.***************/WestAdvis...-an-Alternator




Insert W*E*S*T*M*A*R*I*N*E*.*C*O*M less the "*" in the above


Running dual 1/2" v-belt are more inline up in the 310 amp range.

:faint2: