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302 Mercruiser 888 Project

T

Tcphill3

New member
Hello all, I’m Tyler, a 22 year old with an unfortunately expensive passion for boating, I am new to the community, I’m looking for some help with my 1972 Marlin Leo project boat. It has a 302 Ford Mercruiser, 188. I bought it as a project for my dad and I to work on to spend some time together. It was (still is) in pretty rough shape. Hull is decent could use some filling, sanding, and paint. It hadn’t ran since 2016 when it was last registered. Sat in the elements. We gutted the torn up interior, and carpet. Now it’s just a hull, floor and an engine. I hooked it up to a battery, got gauge lights, verified it had spark, and it popped off some. I rebuilt the carburetor and was able to get it to run for a minute or two but no longer since it wasn’t hooked to water. Huge achievement for me. But now it won’t run again without the starter being engaged, I’m thinking it’s ignition switch/ballast resistor? It has spark when engaged seems to lose it when not. Also the trim will only trim up, and the bilge pump apparently works part time. That’s a side note, the real reason I’m making this post is about the wiring in general. It seems functional for the most part but the previous owners had installed speakers, lights, shitty walmart gauges, and other bull**** horribly bad, ten million butt connectors and rolls of electrical tape. I want to know if it would be worth just ripping the old wiring out and starting again? It seems easy to find a wiring harness that may work but it just seems like a huge undertaking that has halted our progress as of late. We have to pull the engine anyway to put a new floor/fiberglass and epoxy in. Just looking for any recommendations you guys may have about the wiring or the whole project in general, look forward to hearing from you, thanks a lot!
 
Hi, Tyler. Good luck with your project. I've been working on something similar. A 70's era runabout with a Merc 120. I bought it a year ago, full of snow and pine cones. Had not been run for a few years. The boat was free, essentially, since the trailer was worth what I paid for the boat and trailer.

I spent the month of June working on it every day. Each milestone passed revealed the next milestone. A fresh battery revealed that the engine would turn over and generate spark, but that the carb was wobbly. Removed the carb and found all three screws that hold the base to the main section were loose, with one in the bilge. Basically every part that I looked at had to be, at least, tightened from being loose, or restored to like new. Family kept asking will it be ready by July 4th? And it was ready for use July 6th.

Anyway, I feel your pain re the wiring. You need to get a reel of #14 wire, and if something is not working and troubleshoots to a wiring fault, just run a new wire with marine grade terminals. There is a proper marine way to butt join two or more wires. Do that. I wouldn't bother with pulling out the old wiring harness and putting in a new one. Some of the original circuits will be OK. You can run new wires around the dodgy ones.
 
Starting from scratch when doing a complete rebuild would be my thought. Not that you couldn't fix what you have but it will look better and most likely have less problems. The main concern I would have is with the 302 motor because it hasn't been produced in a long time. You might look for a 305 or 350 and do it now.

Either way the 302 was a good motor and if taken care of will last a long time

But now it won’t run again without the starter being engaged
Click to expand...
This is a wiring or switch problem as you mentioned and I would look at the key switch first

You can get new custom wiring harnesses from places like Hardin Marine. Custom just means at has the main connector and you run the wire how you wish then cut end and add connector
 
Where are you located?

If you want send me your phone number thru the message function and a time to call and maybe we can discuss how it all works and what and how to troubleshoot
 
You can get a good used or even new harness that will connect the engine to the helm and gauges fairly inexpensive. I assume only one steering station. The rest of the wiring is for lighting. That's a very simple circuit. Without knowing what else you plan to have....bilge pump, satellite TV, Sauna, espresso machine, etc. it is hard to say. Each device needs its own circuit and protection (I prefer the switch-type circuit breakers). If it gets complex, that is, more than just lights and bilge pump, you should think about a two bank or even three bank battery setup. This gets you into the highly misunderstood world of battery charging and isolation. Don't worry tho, we can walk you through all that. If you keep the boat in the water, that is, not launch from a trailer every time, you must have some way to keep the battery charging so that it won't go flat, kill the bilge pump and the boat sinks.
I guess to answer your question, yes rip it all out and start over. At this point there's no reason to keep it. It'll have unseen corrosion up inside the insulation.
Making your own from scratch isn't too hard to do. Use the marine-grade wire and adhesive lined shrink terminals (buy in bulk on Amazon) The wiring colors are standard and you don't want any wiring less than 14AWG. Several on line marine wire retailers. I use https://www.customcableusa.com (formerly genuinedealz.com) Wrap with woven sleeving or split loom conduit to prevent chafe.
 
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