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87 Mercruiser 3.0L... where to start?

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Derek Reidy

New member
Hello all,

This is my first time posting here and I'm pretty new to boat engines. A friend of mine gave me his 87 Mercury Marathon which has a Mercruiser 3.0L 4cyl. The boat has been sitting in his yard for 4 years. When he put it there, it was running but had some exhaust problems (as he put it).

Anyway, my son and I spent about a week cleaning it out (it wasn't properly covered, gas cap was opened, squirrels must have gotten to all the seat and wall foam, etc). Now I am at the point where I am trying to start working on getting the engine and electrical fixed.

So first thing I did was throw a trickle charger on the two batteries in the boat. The charger claims they both charged, but when I turn the key I get absolutely no power what so ever. Nothing. Lights don't turn on, gauges don't move, etc. I checked all the glass fuses near the gauge cluster and they were all okay. When I went to check the 50a circuit breaker (red button) I can't push it at all. Must have rusted in place.

Anyway, before I ramble on too much, my question is.... where would be the best place to start? Accessory electrical? Get the engine running? Flush the engine? Boil the tank? I have no idea and I'm overwhelmed. Stupid me thought it would be easy to get this thing fixed up but I'm learning its a pretty big job.

I really appreciate any advice and I apologize for asking such a beginner question. I just don't know where else to ask.


Derek
 
Empty fuel from gas tank and have it cleaned,Replace all fuel components from tank to engine,lines,filters, water/fuel separator ETC.more to come!
 
I would suggest inspecting your floor, stringers,foam, and transom if it was left out in the elements. When I got my boat,91 seat Ray with a 3.0, the motor ran great. Interior looked great, but under the carpet, under the floor it was mulch! All wet wood and rotted, foam was water logged. I choose to gut it and redo everything , stringers, foam, floor, recovered with fiberglass. It was quite the job.
If the motor wasn't running as good as it was ( or even running) I would not have done it. Just a heads up
 
Get rid of boat and start with one that runs.............

Unless you understand what you are doing then you will be chasing your butt forever.

If you want to do it right, replace the entire wiring harness...........then all connections will be fresh and new.


Other that that you will need to go over every connection and inspect, clean and make sure everything is perfect.

Oh and get a service manual...........guessing wont cut it...........then you can follow the electrical.......
 
Thanks for the replies!

I've cleaned out the engine compartment and aside from a few broken wires it doesn't look too bad. I looked inside the oil cap and it looked brand new. No gunk or anything. I know that doesn't mean anything but... :)

I'm going to start by replacing the distributor cap, plugs, wires, etc. I inspected the wiring harness and its in pretty good shape. No breaks, kinks or cuts as far as I can see. I'm going to put a battery on and do some connection tests just to see if things are actually GETTING power.

Thank you for the advice on the fuel system. I will definitely replace all the hoses, etc.

I had someone who knows boats come and check the hull and everything and they said it was good. No cracks, holes, etc. There was foam in the walls of the boat (where you would put fishing poles, floats, etc) was all chewed away. Is that there for anything other than padding? Don't know if I need to replace it or not.

I can't really get a better boat right now unfortunately. This was intended to be a project boat and so I'll just have to make due with what I have. I know the stern drive was brand new when they stored the boat. So its about 5 years old now and looks to be in perfect condition. From inspection I can see that the exhaust hoses are all gone (if there in fact were any). Maybe later today I will take some pictures of the engine and then people can laugh and tell me what a nightmare this will be :)

Thanks again.

Derek
 
first the obvious... is the main power switch turned on?
On the up side, when you are done with this and it's running, you will know your boat very well. Engine, drive stuff easy to fix compared to rotten stringers,transoms and major deck issues.

Foam in walls likely there to meet USCG requirements for small boats having flotation.
 
On the original batteries, you most likely need to replace the batteries, did you test them first, did you check the water level before charging? What is the date on the battery? If the boat sat for 4-5 years they were likely a couple years old when it last ran. Thus they could be now 7-8 years old.

Even if well cared for and on a trickle/maintainer during the winter you have to replace batteries every 3-4 years. The trickle charger may think they are charged but they are likely junk.
 
Yeah I'm definitely gonna have to get new batteries. Might as well just to be safe anyway. Today I worked on cleaning up the gauge cluster wiring because it was too hot out to do anything else. All the gauge wiring is in tact. I cleaned all the connectors. Gonna actually test them with a 12v test battery. There are a bunch of "other" lose wires in there. I can only assume those are accessories that the previous owner had. There is a mount for a VHF and a fish finder. I know the old owner also ran wires for the bow light and lights on the side. For that, I'm just going to re-wire everything. I plan on getting marine grade wires. But I'm not sure what gauge to get. I was going to go with 16. Is that okay? Again this is for accessories only.

As far as the engine goes. First task is to take out the old plugs, wires, distributor and install all new stuff. I am trying to find the fuel lines for the boat. Not sure if it is 'boat specific' or if they are generic. The starter looks extremely rusted or corroded. Most likely I'm just going to replace it with a new one. Again the 50amp circuit breaker is stuck. Not sure where to find a new one of those. I wish I knew of a place that had all parts for a Mercruiser 3.0l 4cyl. Anyone know of any? Or should I stick with WestMarine.

Thanks again,

Derek
 
Most parts are universal for the motor... boat has nothing to do with anything.

The serial number is key!!

Most parts can be pirchased from this site... west marine and other stores are for accessories not OEM replacement parts....which is exactly what you should be using!!
 
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