1983 merc 260 -- upgrade ????

[wellcraft-classic210]

Hi
I am looking at a boat with a 1983 Merc 260 -- 350 v8 alpha one project -- I know its old iron but it seems pretty well preserved.

I know it has a quadrejet & thunderbolt ignition --and is rated fro 260 hp // I suspect its original but not 100% sure

My question is -- what are the main things I should watch out for & are their any good upgrades to consider such as;

Did the thunderbolts come on that year and did those use points & condensor ?
Is the exhaust manifold style a concern? I think it differs form a 1988 I had.
Would a Vortec head upgrade make sense & add much HP?

Any other advice is welcome -- Thanks!!!

 

[81 Checkmate]

Kiss.....Keep it simple stupid......Thats what id do...


Thunderbolt 4 should be electronic ignition, Cap/ rotor and sensor

Exhaust manifolds..... visual inspect....Been in salt proly need replaced


Vortec heads are only goning to put more stress on a old motor and cost you boating time........Change the fluids/ dont over heat the motor and enjoy the boat.

 

[achris]

Vortec heads are good for about 20hp. Which translates to about 1.5mph... Not worth the pain and cost if you ask me.

 

[NHGuy]

That motor has lots of torque. I'd run it as is too. Make sure your plugs, cap, rotor, and ignition wires are good. Keep good fluids in it, change the impeller and bellows on schedule. And go!
ps. with the cool temps boat motors run you can get away with some extra timing. Maybe 32 to 34 degrees all in. Just listen for the clatter of detonation, if it does that, back off the engine speed til you can take out some timing. Factory spec is 8 degrees at idle, which at full advance is only (I think) 28. So you set base to 10 or eleven degrees then rev it a couple of times to check total timing. you can see what your advance gets. I think it adds 20 degrees. So 11 plus 20 = 31 all in.
Hotrodders run 34 degrees on 350's a lot.

 

[achris]

Depends on the module, some are 22, some 24.

 

[Bondo]

ps. with the cool temps boat motors run you can get away with some extra timing. Maybe 32 to 34 degrees all in. Just listen for the clatter of detonation, if it does that, back off the engine speed til you can take out some timing. Factory spec is 8 degrees at idle,

Ayuh,..... You 'n I can do that, We know what We're doin',... We're the ones answerin' most of the questions here,....

I'd recommend against it generally,.....

Detonation is sometimes very hard to hear, Especially by the untrained ear,.....

I dare say, Detonation is probably the #1 Killer of boat motors, usually due to a Lean condition, but hot timin' will hasten the situation,....

For such an old motor,.... I'd enjoy 'er as she is, 'n start plannin' the replacement motor, from the Block on up,.....

That's when ya go to Vortec heads, 'n center-riser manifold conversion,.....

The Vortec heads can really shine, when matched with mirror image pistons, 'bout .043" quench, 'n close to 10:1 compression,....

Fresh tight heads on a tired ole lower end block, many times just hammers the tired rings into bad blow-by,....

 

[NHGuy]

I might be the next one to experience that, check out my new-to-me boat in my sig.
I've always liked the idea of combustion chamber mirroring pistons with good quench. And I'm pleasantly surprised that we can put that much compression in. Woo hoo, saving for parts.