Need help with tach ASAP

[Fabrimacator21]

I just bought a tac for my boat and the instructions are telling me I need to find a 12v wire that only has power when the IGN is in the "ON" position. Problem is I can't find a 12v wire that doesn't have power when the key is in the "ACC" position. Can I run it to a wire that has 12v power on accessories as well as IGN or will it blow up? I do have a fuse that will be wired in.

What amp fuse should I use?

This is a 305 chevy.

I'm trying to get this done before my storage unit closes so I need an answer as soon as possible.

Thank you.

 

[4X4HIGH]

You just need a 12V source in the "run" position not necessarily in the accessory position but that wouldn't hurt if it does. Just make sure there is no power when the ignition is off or you'll find a dead battery quickly.

 

[Fabrimacator21]

You just need a 12V source in the "run" position not necessarily in the accessory position but that wouldn't hurt if it does. Just make sure there is no power when the ignition is off or you'll find a dead battery quickly.

Awesome, thanks.

What amp fuse would you recommend?

Also I'm not sure which is pausitive or negative on the coil... is the side that says BATT hot?

 

[4X4HIGH]

The negative side of the coil goes to the distributor which is where you want the green tach wire.

I don't ever recall a tach using a fuse but it's been a LONG time since i've installed a tach.

 

[Fabrimacator21]

The negative side of the coil goes to the distributor which is where you want the green tach wire.

I didn't see any wires going to the dizzy... I should mention that this is a 1978 "points" motor.

Theres a little black rubber box looking thing that bolts to the intake manifold and has a couple wires going to the coil. Don't know if that helps.

 

[4X4HIGH]

Since this is a boat you might want to grab a couple pics and then i can help you easier. All GM cars were HEI starting in 1975 but being a boat they could have easily kept using points dizzy's. You should contact ryoken as i think he's a boat mechanic and could help you quicker.

 

[Fabrimacator21]

Pm sent. What would you recommend for a fuse? 10 amp?

 

[82355]

If you really have a points distributor, I would recommend swapping in an HEI (just make sure to remove the ballast resistor).

Martin

 

[ryoken]

haha, you guys'd be surprised how many boats are running around with points... first tune up, I'm selling em electronic!

anyway, as mentioned in pm and here... tachs run off the neg of the coil, as does the dizzy wire... the tach should also have circuit protection on it's 12v supply... usually you wire it right into your instrument power source, utilizing it's circuit protection... but an inline will work fine too... 10 amp will be more than enough, as most know, circuit protection is a function of wire size and length....

whats the marine package? is this Merc?

 

[Fabrimacator21]

Ok... 10 amp it is.

Just an old 1978 200hp omc 305(chebby). Is that prop shaft hp or flywheel hp? Says 200 on the valve covers which leads me to believe it's flywheel.

Almost got her done. Just have to finish bending up the holder for the tac(didn't realize I had no way to keep it in the hole until I started to wire it).

I've thought about goin HEI but honestly I don't want to deal with it and can't afford it. It runs good and hasn't caused a problem yet. As long as I remember to turn the key off when I beach it all should be good. It does have a mallory points dizzy though which I don't think came factory.


Gonna be a long night tonight... didn't make my storage deadline so I got a list of chit to do. Gotta get the trim unstuck and swap the water pump/alternator belt(HUGE PITA in this boat as you have to jack the whole front of the motor up to get the belt around the motor mounts).

Wish me luck.

 

[4X4HIGH]

Keep in mind that the alternator, starter, air cleaner, and dizzy are all Mmarine specific and if a coast guard ever boards your vessel and happens to check things out and finds that any of that is not marine then it won't be fun for you. It all has to do with spark and fuel liking to explode when mixed in the bilge.

 

[Fabrimacator21]

I'm still finding things that are marine specific... brass freeze plugs, stainless impeller water pump, etc. It seems marine stuff isnt' cheap... a water pump alone is 200 bucks compared to 30 bucks for automotive.

Explosions are a big problem with boats which is why I won't even turn the key over until I've had the blower running for at least 2 minutes. Saw a beatiful V-drive burn to the ground/water when I was 6... lesson learned. He didn't run the blower before starting and it went up like a mexican fireworks show.

Thanks for the help guys... ck5 is still the chit even when it comes to boat motors...

I've been spending alot of time over here www.iboats.com and there isn't a section for motors. Learned alot though... sort of the ck5 of boats.

 

[cuervo]

I've been a boat owner for a long time and boating most of my life. It seems that blowning up boats and crashing them in to stationary objects is a passtime for some people. Running the blower before starting is must and it's when people get in a hurry thinking it wont matter this time is when they get hurt.

I love taking the family out on the lake for some skiiing, wakeboarding, and AirChair riding.

I spend far to much time on the lake and it will only get worse with retirement!!

The worlds biggest float. Holds 10 people and has two built in coolers!

 

[ryoken]

blowning up boats and crashing them in to stationary objects is a passtime for some people.

job security baby!

had to glass up a basketball sized hole in a swim platform yesterday.......

 

[cuervo]

job security baby!

had to glass up a basketball sized hole in a swim platform yesterday.......

Damn, I know that sucks. What happened?

 

[ryoken]

eh, probably screwed up backing it in to his slip, smashed the dock.... I have customers that I'm glassing/gelcoating their platforms, transoms every year....

I've done some MAJOR crash jobs... had one a few years ago that was a $250,000 insurance gig... 63'er coming into the marina, canopened the whole side of the boat on all the slipped boats bow pulpits...