1985 Mercruiser 305 Engine - How long do they last?

OK, I KNOW there are a million variables one needs to know to even guess at an answer for me, but I'm looking for just a general answer as to how long my engine might last. the reason is that I am doing some interior work but I don't want to do too much if it's likely to crap out on me soon. Here's what I know about my engine (sorry, not an engine guy, but I'll do my best so you'll hopefully know what I have).

1985 19' BR. Interior will be nice to very nice depending - for a 20 yr old boat. Structurally very sound - I'm replacing part of the floor/stringer repair but transom and engine mounts not rotted.

Engine: 305 "small block" 8-cyl; 200hp; 2bbl, alpha1 outdrive, 1.65:1 gear ratio (not sure); I THINK model is 898.. Starts right up, no problems at all in the 3 mths I've owned it - maybe 20+ outings. I THINK it was well maintained, I KNOW it was for the past 10 years. Mechanic I bought it from rebuilt the outdrive and gear box 2 years ago. No hour meter so no idea how much it was run.

Anyways, again, I'm just looking for a rule of thumb on these. Do they go downhill fast after 20 yrs or so? Do they last "forever" if maintained? I want to make an informed decision on how much I should fix up the interior. In looking for a cheap used runabout boat ($3k or less) I picked this one because it's the only one in that price range I saw in decent shape AND having a 200hp V-8 engine that seemed to run very well.

I KNOW the resale value isn't much no matter how much work i do to the interior, that's not a consideration. I'm only interested in keeping it until it becomes too big a pain/cost to keep running well for family boating and towing skiers/tubes/etc. It will be basically worthless then anyhow.

thanks for any info.

Re: 1985 Mercruiser 305 Engine - How long do they last?

Not that many ever wear out. At least not on recreational vessels. More die from improper maintenance than anything else. They'll rot before they wear out. In saltwater, corrosion is going to get it within 10 years. In fresh water, they can easily last decades. With closed cooling, a few decades more.

Re: 1985 Mercruiser 305 Engine - How long do they last?

Thanks. Oh yeah, some more info - fresh water only since new, open cooling system.

Re: 1985 Mercruiser 305 Engine - How long do they last?

I would think 1500 hours or so. At 35 hours per year (that is the average use of an i/o boat in my area), that would be 43 years.

Re: 1985 Mercruiser 305 Engine - How long do they last?

Ayuh,......

As Noted,.....
SBCs Rarely Wear Out in Boats........ Millions of them are Killed though.......

Re: 1985 Mercruiser 305 Engine - How long do they last?

tmh,
I have an '88 - since it was new. In the bumpy course of my learning curve (pre-iboats days of course), I have almost sunk it - water got over the starter (bad hull sealing by mfr - not really my fault), overheated it, froze it solid for at least two or three nights (dam deer kicked the cord out of my "safety" heater), let water leak into the cylinders thru the flame arrestor mounting stud (due to leaky canvas), let it sit unused for 2 winters sandwiching a full summer while I built my house(properly winterized, though - I do know how to do that), run it with the battery disconnected (a real no-no according to the gurus here).......and that's just what I remember. :% Lived it's whole life on Chesapake Bay water - which is not the cleanest & can get pretty salty late in real dry summers. In between all that, believe it or not, I have maintained it reasonably well - regular oil changes & tune ups. And it's still running like a top. If I had to sum it up in 2 words - bullet proof. If yours has been treated at least a little better, I would bet it has quite a few more years in it.

Re: 1985 Mercruiser 305 Engine - How long do they last?

OK, thanks for the info,all. I just wanted to make sure it was likely the engine will hold up as long as I take care of it. I'm going ahead with some inexpensive interior upgrades (in relative boating terms - still a hundred here and a hundred there adds up!).

I took out a arount 250 lbs of waterlogged foam when I tore the floor out and I'm adding Smart Tabs and a new prop, so I'm excited to see how it runs in the spring. I should be much happier with the ride, although it wasn't too bad before.