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Old 25-08-2011, 10:58   #1
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7.4 MerCruiser Engine Life

Good day everyone.

I'm looking to purchase a Sea Ray Sundancer 340 by the end of the year if the stars align and everything makes sense.

Part of my research is the engine life as the year's I'm looking at are 1998 - 2002 and I'm concerned I'll have to replace the power plant shortly after acquiring the boat.

I understand freshwater used boats are more ideal vs. salt but I'll be living in FL so it would be nice to not have to ship the thing halfway across the country. But, if it means not have to spend some serious coin on a couple new engines then I'm game.

Anyone have any experience or know some good references to find out the typical hours or years one would expect out of this engine?

In addition, I'm new to boating so this may be a dumb question but I'm not the most mechanically inclined individual. When it comes to relatively simple fixes I have no problem pulling out a wrench but replacing manifolds, etc., I'm out of my comfort zone So my question is, how do most owners perform maintenance on their crafts and what are the pros and cons to doing it yourself?

Thanks for your help!
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Old 25-08-2011, 11:04   #2
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Re: 7.4 MerCruisers Engine Life?

Not sure which engine base the 7.4 is, but the 350 chevy engine (5.7?) is reasonable $ to replace as there are so many out there. There are small shops up here that do only those engines, making them pretty darn reasonable.... at least according to a buddy of mine whose been using them for years. I have wondered the same thing as you.... how long do they last? I think manifolds need replacing alot from what I hear. An engine that is run regularly is usually better than one that sits a lot and has low hours.... non-use damages marine engines.JMHO.
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Old 25-08-2011, 11:31   #3
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Re: 7.4 MerCruisers Engine Life?

SeaAir, A thorough survey by a qualified mechanic will be the only answer to your questions. I can tell you that the engine itself is not so much of an issue as the peripherals. Things like the exhaust riser, which need to be replaced regularly in salt water, can easily cost a few thousand if done by a mechanic. There are several other parts that require replacing that might already be past due. I suggest you contact a local Merc dealer for the specifics. Hope it works out. Chuck
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Old 25-08-2011, 11:38   #4
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Re: 7.4 MerCruisers Engine Life?

Quote:
Originally Posted by Cheechako View Post
Not sure which engine base the 7.4 is, but the 350 chevy engine (5.7?) is reasonable $ to replace as there are so many out there.
The 7.4 (454) is a big block. The 5.7 (350) is a small block. They are not interchangeable. The direct replacement from merc. for a 7.4 was the 8.1 (496). This too has been discontinued and replaced with the 8.2 (502).

I replaced a 7.4 2 years ago with a 8.1 remanned that was about 10K (15K) new. I'm not sure of the 8.2's. There are still 454's out there to be had. I haven't priced a replacement long block.

I replaced mine after about 12 years and 400 hrs. (freshwater cooled).
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Old 25-08-2011, 23:44   #5
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With proper maintaines you can 2000 hours
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Old 26-08-2011, 00:31   #6
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Re: 7.4 MerCruiser's Engine Life

I don't know about the engine but at the slipway near where I keep my boat I see a steady stream of boats having major operations on their sterndrives (inboard/outboards).

One theory was that the owners forget the anodes and they don't last long after that but I'm only repeating scuttlebutt.
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Old 26-08-2011, 10:01   #7
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Re: 7.4 MerCruiser's Engine Life

i know theyre not the same engine, just trying to indicate that when deciding what boat to buy, a 350 is more economical to repair as there are a million of them out there. alot of these type of boats have one or two engines, two 350's might be better than one 454... hard to say I guess. I agree with Boracay, outdrives are always broke!... except maybe the Volvo duo props or bravo ii's
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Old 26-08-2011, 10:08   #8
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Re: 7.4 MerCruiser Engine Life

Each engine is going to be its own case, even identical engines from the same year. This is because engines are treated differently by their users along with problems that can occur in one engine and not in the other by luck of the draw.

Hire a professional engine mechanic to check out the particular engine that you are interested in.

Outdrives can be very reliable if treated and maintained correctly. Most people who own them don't seem to know much, leave them in the water all the time or ignore service intervals. When abused, owning an I/O is like owning two engines.
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Old 26-08-2011, 10:26   #9
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Re: 7.4 MerCruiser Engine Life

And, the Searay Sundancer 340 probably has TWO of those bad boys - so that's like FOUR engines! And no way to get the outdrives out of the water unless you put the boat on a lift.
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Old 28-08-2011, 10:13   #10
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If well maintained and cared for a gas marine engine can last for 1500 to 2000 hours.
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Old 28-08-2011, 10:34   #11
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Re: 7.4 MerCruiser Engine Life

I just put a 7.4L (454) reverse rotation in my inboard ski boat 2 months ago I purchased a long block then swapped my intake, carb, pumps ext myself and installed it. The long block was $2600 which I was happy with. However I can pull mine into the garage to swap the engine a boat like ur talking about would require something big to lift the motor so you would have labor but the actual engines aren't super expensive.
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Old 28-08-2011, 10:44   #12
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Re: 7.4 MerCruiser Engine Life

I have a 7.4L in a 1996 Maxum with 325 hours on it and it runs like brand new. Its been in saltwater and fresh. I make sure I flush the engine after being in the saltwater. I agree that you should be able to get at least 2000 hours on a well maintained engine. Unless something happens to damage the block ie freezing, overheating, etc. they will last a long time.
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Old 28-08-2011, 13:02   #13
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One other thing that is worth while doing if not already done is to put fresh water cooling system on it make sure you include the manifolds will save you tons now you will only have risers to change evey couple years Specially in the lower latitudes the salinity in the water is higher. My advise is. Fwc lots of oil changes and drive servicing one of the best thing you can yourself is to keep bilge dry and engine as clean as possible keep up on paint and so forth
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Old 28-08-2011, 13:44   #14
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Re: 7.4 MerCruiser Engine Life

The Searay has excellent engine access. Even if you do need to repower sometime in the future, you could find a dock that you can back into (depending on the location) and actually have a crane at dockside do the swap. The eng's are side by side (only 2 of them) and they should be fresh water cooled (vs raw water) and this will help eliminate some corrosion issues - These boats are made for Salt water. The best preventive steps you can take are to make sure the engine sacrificial anodes are changed regularly, that along with reg oil & filter, fuel filter, air filter changes. Basic maint can make a very happy engine.
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Old 28-08-2011, 16:49   #15
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Pulling engines with the drives on it is not easy If they are inboards with shafts no problem but with drives is difficult and can lead to other issues With drives all the alinement is done through the transom assemblies I would not recommend this method
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