Almost Newbie looking for input

Glad I found this place. I think I will find lots of info to help me along my way and with any luck I can offer some assistance to others too!
I am a 25 Licensed Auto Mechanic - 15 yrs building/racing/maintaining stock cars as a hobby with my brothers so I have mechanical/modification knowledge but I am pretty new to Marine.

Here is my situation. (lol heard that before from a boater?)
Looking to use this boat for entertaining the kids with wakeboarding and tubing primarily on small lakes. I am not looking to have a speed machine but I don't want to be out run by a old lady swimming the shore either.


Interested in buying a 1986 Cobia 18 ft Bowrider (18vbr I/O) Hull is in good condition, interior decent, trailer in good condition.
This is a project some one started and I will have to go back to original or start fresh with his idea. Most would turn and run after looking at this unit but, I don't have much in the way of cash to spend so a project is a must. Time = $ but my time working on this = FUN HAD BY MY FAMILY!

Original power was a 120 hp OMC ( I will have original engine which by his account has a bent pushrod) and Stern Drive Model #980701 (Stringer Drive from what I can figure)
He installed (partially) a 4.3 V6 from a Blazer. He stopped with the engine installed but as he puts it "not wired and exhaust install still needed"
I would remove the engine and properly rebuild it.

Questions are (add info as you see fit)

1. Should I even consider continuing with project as is or go back to the 120 hp powerplant?
2. What situations/issues do you see me running into if I go with the 4.3l ??
He has exhaust manifolds/and risers it appears to be properly mated to the outdrive. I will need carb/intake/marine starter/distributor/fuel pump and ?????

3. Camshaft.... anyone know what specs are on the marine cams that would be used in such an application? or a good location to find this info?

4. final gear ratio based on what I could figure using the GLM parts listing would have
4cyl configurations using upper 21/18 lower 2.0:1 = 2.32final
6cyl 4.3 using 21/19 upper and 1.83:1 lower = 2.01final
(for referance a 305 would have 2.25 and a 350 2.40 from what I could figure)
Now from a automotive point of view that isn't much ratio diff.
Marine......... well I sure as heck don't know. Prop change/tweak needed or pretty close see how it works??


What you think????????????? AM I NUTS OR ?????????
Thanks in advance for any assistance/info provided.

 

gimlit,
I don't know a lot about boat engines yet, but I am pretty sure you don't want to put an automobile engine in a boat. Sparking hazards with explosive gasses present, condensation/corrosion problems, not enough compression, etc... I am surprised nobody else has responded to your post.

opinions anyone?

 

Fishfinder ie correct about the Electrical hasards. You should use a marine starter, alternator and ignition. All are sealed to prevent sparks in the motor compartment.

In addition any gasgets in contact with sea water should be Marine type or at least S.S. or copper. Flame arrestor should be used in place of an Air Cleaner. Marine Carb must be used. Marine water pump w. Brass or S.S. Impeller is a Good idea.

Unless you need more speed, I would stay with the 4cyl, 120 - less changes need be done - you would need a different prop at least, if not a different out drive (ratio). The 4cyl will give you 36 - 42 MPH, The v6, 42 - 46. Not worth the changes & cost in my opinion.

The 120-140 HP, 4 cyl are Good reliable motors, which basically came from the 1960,s Chevy II,s