1999 5.7 mercruiser any experiance or opinions?

[b.staub]

Anyone have any experiance with the 5.7 mercruser and do you know how efficient it may be compared to the outboards? Any idea how long these may last if they were used in fresh water only. Alot of maintenance? Things to look for? Thanks

[fitz73222]

Well think of the efficiency of that engine on land; the 350 Chevy. A bulletproof engine that was always a little thirsty. Relatively low cost to rebuild. I've never been a fan of gasoline inboard engines and stern drives. I guess in freshwater the maintenance is somewhat reduced but still quite extensive compared to outboards. I never have liked the power to weight ratio, draft, holeshot, fuel economy, fire potential or loss of deck space asscociated with them. The full height transom is nice however. If you are using one in salt water and don't believe in a stringent maintenance protocall, don't buy one unless you like spending a ton of money at the repair shop!

[GoneFission]

I have a pair of 5.7 Mercruiser inboards on my "other" boat.  Like Fitz says, they are 350 Chevy blocks, so parts (as long as they don't have to come from Mercury) are cheap and easy to find.  The unique Mercury ignition system is expensive if you have to replace it, but they are also very reliable.  Carburetors are standard Holly or Rochester models, but intakes are usually unique.  It is also common to have the engine reversed so the flywheel is toward the front to allow for easier hookup to the transmission.  Fuel consuption is reasonable - the carb engines do better than all but the best DI outboards - and the newer fuel-injected Mercruisers are very stingy with fuel.  And you can't go wrong with that V-8 rumble at idle...  

You don't mention whether the engines are fresh water cooled or raw water cooled.  That makes a big difference in salt water; not so much if run only in fresh water.  A raw water cooled inboard engine in salt water is only good for about 1000 hours, but fresh water cooled engines normally run 2000-2500 before needing much work.  You need to know the use of the engine (salt or fresh) and type of cooling before you make a decision.  

Like all 4-stoke engines, you need to change oil, do tune ups (plugs, filters, etc.) on a regular schedule.  All have had hydraulic lifters since the 1970s, so you don't need to adjust valves.  Check for oil leaks - especially around the rear of the oil pan, the front and rear shaft seals, and valve covers.  The rear seal/oil pan leak is fairly common on these engines and a pain to fix without taking the engine out of the boat.     The valve cover leaks are easy to fix with new gaskets.  Also look the exhaust risers over carefully, as they do sometimes crack and leak.  That's a $300 to $450 repair unless you get lucky.  

What transmission are you planning to use? That matters too!

[b.staub]

This must be raw water cooled because I can see no radiator.  There is a large hose on either side of the motor which I  would think is the raw water cooling. It states that it was never run in salt water. The boat must have been kept in the water though because the outdrive has coroded. The bottom does not have bottom paint though so I guess they corrode enough to have the paint come off some even in fresh water. I do plan on using this in salt water but I will be trailering it. Do you think this will be a problem if I'm flushing it after use? Can I use a standard set of cups to flush this or does it need to be run in a barrel? How do I find out what type of transmission it has. It has a black mercruiser outdrive on it. Is there a different size or something? What year did they start the fuel injection?

[Capt Matt]

The main problem with the set up is not the motor but the outdrive, they draw a lot of water, are expensive to fix and don't last long in salt water.  The biggest draw back with a gas inboard is gas fumes in the bilge + a spark  = you turn the key and explode.
Capt matt

[marco]

1 of my other boats had a 5.7 mercrusier IO setup. The motor was bullet proof, the drive on the other hand was nothing but a maintenance (money) pit. Went back to outboards and I'm never going back. Just MHO

[GoneFission]

As a wise person on this site once said, "this post is worthless without pics."  Post some pics of the engine and outdrive and maybe we can provide some relatively educated advice.  Otherwise, we are all just shooting at the moon (not that mooning is always bad!).

[capnJ]

Lets separate fact from fiction first off. Inboard Gas engines are very safe to operate. Explosions of inboard  gas engines since 1970 are so few that it is hardly worth mentioning. Outboard engines(newer) get better fuel burn rates than inboards. Maintenance on them from a financial stand point is not much difference. They both have plugs, wires, fluids, etc. and all should be maintained as required. My boat is a 1986 Aquasport 290 TM. I am the second owner since new. The hour meters on the boat read 3721 port and 3753 starboard I re-powered the boat in 2006 the hour meters on the boat then read 2400 hrs give or take a few. They were the original engines that came with the boat. They are raw water cooled and this boat has always been in saltwater. If you take into consideration the cost of an outboard engine to the cost of an inboard engine or to rebuild and inboard engine there is no comparison. A couple of new outboard 250hp engines can run you in excess of $17,000 each. I bought new long blocks for mine put all my hanging parts on the engines and spent less than $5000 for both. (I did install them myself). I would have to save $29000 in fuel over the life of the engines just to break even and lets be honest the average boat owner doesn't keep a boat longer than 7 years. Just something to think about Good Luck

[GoneFission]

cJ brings up a good point.  You can almost consider the block on a 5.7 or 7.4 inboard a disposible item!  

The outdrive on an I/O setup is much more expensive than the engine.  I ran a pair of raw water cooled GM blocks on my Chris-Craft Connie for about 20 years and never really had a problem, but if I did, I could have changed the engines/blocks out for about $2,000 each.  GM has made millions of these, and they have pretty well bullet-proofed the engine.  Most problems I see today on these engines are from either:
- overheating (did not maintain the water pump or clean the strainer) or
- something non-GM failing (water cooled exhaust risers) or  
- freezing in very cold weather (Bubba don't need to winterize!)

But they are gas engines in a closed space, so you DO need to run the bilge blower before starting, and a fume detector in the engine compartment gives you piece of mind that all is OK down there...    

My $0.02 - and maybe worth that much!