Electronic ignition & tach question

[John Carpenter]

Last week I replaced the original Mallory dual point ignition in my '78 Chris Craft...Chevy 305 engine...with a GM HEI system made by Accel. The difference in the way the boat runs is just amazing. The only problem is that my tach no longer works. I know for sure that I have more power and rpms than before and don't want to over rev the engine. Do I need to install a different type tach or can I make the original work with a different wiring configuration?

 

[snapperbait]

Re: Electronic ignition & tach question

Hi Relentless.. Is this the distributor with the ignition coil housed on the cap? <br /><br />Have you gone and done what I think you may have? Installed a regular old distributor where you need a marine distributor?

 

[ahein]

Re: Electronic ignition & tach question

Hi Snapperbait,<br />Just curious why you believe the GM HEI with the coil housed in the distributor is a bad thing? I have an '87 Volvo Penta AQ225 (GM 305 c.i.) with this set-up and it seems to work fine. However, I bought the boat with this distributor already installed, so maybe I'm missing something. What are the advantages of having a seperate coil or disadvantages of having the coil in the cap?

 

[FreeBeeTony]

Re: Electronic ignition & tach question

I was going down the same path, using an automotive HEI distributor in a marine application. What I learned is this: the marine distributors are equiped with venting to allow the gas fumes to escape from under the cap where automotive distributors do not have this venting. I found a conversion kit manufactured by Pertronix that installed directly into my marine distributor and worked fine. If you decide to go this way I would recommend the Ignitor II version, it has some built in protection circuitry. Good luck......

 

[McKenzie]

Re: Electronic ignition & tach question

where did you hook up the signal wire? is the tach signal wire hooked up to the negative coil wire?

 

[snapperbait]

Re: Electronic ignition & tach question

Marine distributors have spark arrestor screens over the vent holes to keep any stray sparks out of the engine compartment.. Most automotive distributors do not...<br /><br />A build up of gas fumes and stray sparks in an engine compartment is just asking for trouble, usually in the form of big KABOOOOOM! <br /><br /> I'm willing to bet that if your insurance co. finds out after the big explosion that you have an incorrect distributor and it contributed to the explosion, the insurance co. will most likely not pay for any damages to your boat and you will be held liable for injurys to anyone who was aboard...<br /><br />Not a thing wrong with an HEI distributor in a car or truck where it belongs...

 

[John Carpenter]

Re: Electronic ignition & tach question

I am aware of the fact that some consider this to be an unsafe setup...however I can see no difference between the HEI by GM and the Pertronix unit. They are both sealed units...and I would think that either would have to be safer than the dual point setup I removed. If someone can show me how this is wrong I will cheerfully remove the unit.<br />As regards the tach wire...there is a terminal on the distributor for the tach...just get nothing when I connect to it with the same wire used by the old setup. There is no coil to hook up to, it is gone with the HEI distributor.<br />I am not trying to be argumentative here, just dont' think what I have done is unsafe. I have been wrong before.

 

[McKenzie]

Re: Electronic ignition & tach question

under the cap, what is the tach terminal connected to? you might need a tach adapter, summitracing.com has them.

 

[John Carpenter]

Re: Electronic ignition & tach question

McKenzie<br />Don't know really...it seems to just disappear into the body of the distributor, but I would have to check it out to be sure. Thanks for the suggestion though...I'll check it out. Probably beats buying a new tach.

 

[McKenzie]

Re: Electronic ignition & tach question

In the rare event that you have access to an oscilliscope, you could see what kind of signal is coming out of that terminal, if any.

 

[John Carpenter]

Re: Electronic ignition & tach question

As a matter of fact I own an oscilliscope...belonged to my father who was an instrument engineer. There is an outside chance that I could figure out how to turn it on....but I do have a friend that could use it. Thanks for the tip.