How Long will a Mercruiser last in salt water

Prophammer

Chief Petty Officer
Joined
Jul 2, 2010
Messages
466
I'm thinking buying a stern drive boat and using it in salt water, Mercruiser or Volvo Penta, probably with raw water cooling system, it will be a trailer boat, and I will flush the cooling system after saltwater use, how long will the block, risers, etc. last before they rust out?
 

Bt Doctur

Supreme Mariner
Joined
Aug 29, 2004
Messages
19,111
block over 2000hours, manifolds 6-8 fresh or salt, 4-5 for risers, give or take a few
 

bruceb58

Supreme Mariner
Joined
Mar 5, 2006
Messages
30,476
He meant years for the manifolds and risers.

I use Neutra Salt system on my Volvo. Adds some life. I still flush but I run the Neutra salt right before I pull the boat out of the water and again right before I turn the engine off after the flush.
 
Last edited:

achris

More fish than mountain goat
Joined
May 19, 2004
Messages
27,468
Ran an I/o in salt for 6 years. A set of risers and three gimbal bearings later I dumped it for an outboard

Why the gimbal bearing problems?

I've run my own I/Os and outboards in salt since 1986, and with my father since I can remember. It all comes down to maintenance. If you neglect a machine it will let you down. But service and maintain it properly and dutifully and it will give years of good service.

Ok, for I/Os there is the issue of elbows and manifolds. They do need to be replaced regularly, but my previous engine (a 1994 4.3LX, in a friends' boat which I still maintain) is still on it's original shift cable, uni joints and gimbal bearing. My current engine, 2006 4.3MPI, is also still sporting all original components in the transom assembly and drive (apart from the water pump impeller)... Last year I did the first replacement of the exhaust elbows. The only other problems I've had were my oil leak (a GM problem and it was also a problem with Volvo I/Os and GM cars with that engine of that year. Find my threads on the problem)... and a fired IAC. That was a $49 fix and has been perfect since.

As much as I dislike Merc (find my oil leak threads as to why), if I was to buy an I/O it would be a Merc. Reasons... Parts are far easy to get and WAYYYY cheaper. More Merc I/Os on the water, better dealership network and more people with Merc I/O knowledge... (and yes, I know I'm going to get a thousand Volve people who are going to argue that.... but that's how I see it)

Chris.....
 

alldodge

Moderator
Staff member
Joined
Mar 8, 2009
Messages
40,719
Fresh water a long time, 1995 Rinker still on original manifolds. 1994 Formula, there sitting in the back of the shop but still good when removed I think 3 years ago
 

bruceb58

Supreme Mariner
Joined
Mar 5, 2006
Messages
30,476
Parts are far easy to get and WAYYYY cheaper.
I am curious what parts you think are way cheaper. I just did a quick comparison of a driveshaft that includes u-joints for my Volvo drive vs a Bravo. Merc price was $560 and Volvo was $400. So what parts are WAYYYY more?

I just compared OEM exhaust manifolds for a 7.4L. Volvo $523. Merc $470. I guess that is cheaper.

I always hear this and it was definitely true in the old days with the 270/280/290 drives but I think it's just some thinking that just stuck around.

Of course with a Volvo, I rarely have to buy parts for it so maybe that's the issue! :)
 
Last edited:

bruceb58

Supreme Mariner
Joined
Mar 5, 2006
Messages
30,476
Ran an I/o in salt for 6 years. A set of risers and three gimbal bearings later I dumped it for an outboard
You do realize that running in salt water or fresh water shouldn't matter to gimbal bearings right?
 

thumpar

Admiral
Joined
Jun 21, 2007
Messages
6,138
What's the deal with the gimbal bearings? They are good for years and years unless they get water in them.
 

dan t.

Lieutenant Junior Grade
Joined
Feb 28, 2008
Messages
1,131
The trick to making risers last in salt water is to use pencil anodes in the drains, If they use a 1/8 plug, drill and tap them out to 1/4 npt,, these anodes will last all season.Replace with new ones every year. I had a set of Merc risers last 8 years and replaced them as a precaution not because they were leaking, I credit their long life to the pencil anodes.
 

Lou C

Supreme Mariner
Joined
Nov 10, 2002
Messages
11,831
12 seasons moored in salt water Long Island Sound region...
2 sets of manifolds (OMC one piece)
1 gimble bearing
1 driveshaft bellows
1 set of trim lines (cut by barnacles)
starter
circulating pump
2 carb rebuilds
impellers every other year.

Still original:
engine long block never touched
alternator
trim pump
trim rams
u joints
upper and lower drive gears

Its all about the maintenance. If you don't maintain it you will have problems. An OB will be less maintenance till it starts to have expensive problems and then it will cost more than an inboard repower. But if you don't want to do the I/O maintenance the OB can be less work on a year to year basis.
 

crazy charlie

Vice Admiral
Joined
May 22, 2003
Messages
5,374
Go with mercruiser.Parts are reasonable,available,and just about anyone can work on them.Make sure the engine temp is high enough for the tstats to open when flushing and all will last a very long time.Charlie
 
Top