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  Why Not 5,000 Hours on an Outboard?

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Author Topic:   Why Not 5,000 Hours on an Outboard?
elaelap posted 06-03-2004 01:10 PM ET (US)   Profile for elaelap   Send Email to elaelap  
It's been blowing a small gale out here all week, so no salmon fishing, and having nothing better to do (except of course family, work, son turning 18 and graduating high school, and other such inconsequentials), I've come up with this question: Why shouldn't I expect to get at least 5 thousand hours of use out of my new four stroke outboard, rather than the 2-3 thousand that most folks predict is reasonable? I've got 150 thousand miles on my 9-yr-old Dodge V8, heading for 200 thousand. Let's say I average forty miles per hour in my truck (a high estimate for my auto use, I suspect). If I've done my math correctly, that means I will have about 5 thousand hours on the engine at 200 thousand miles. Why shouldn't I expect to do as well with my outboard motor, or is the premise of my query essentially flawed? What say you, experienced outboard motorheads?

Tony

Peter posted 06-03-2004 01:33 PM ET (US)     Profile for Peter  Send Email to Peter     
Marine engines are subjected to a much higher average load during their operating life than their automobile based counterparts.
kglinz posted 06-03-2004 02:14 PM ET (US)     Profile for kglinz  Send Email to kglinz     
I think it would be really interesting to see info on why outboard motor are replaced. How many are "worn out" compared to motors that fail from overheating, lack of lube, something caught between the ports and the piston, or water injestion. When a motor fails the statement you hear is it "blew a powerhead", not it wore out. Old motors, particularly single carb motors ran forever. Multi carb motors develop a carb problem, but it isn't noticed until a cylinder fails from lack of lube. I think if an analyses was done it would be quite interesting. The problem seems to be that often the motor manufacture doesn't know what the problem is, or won't admit to the problem.
Moe posted 06-03-2004 02:34 PM ET (US)     Profile for Moe  Send Email to Moe     
Your outboard will be running 4000 - 4500 rpm much of it's life. Due to the transmission, your Dodge V-8 will run about half that most of its life. If you'd run it between 2/3 and 3/4 of it's redline rpm most of its life, you'd have rebuilt the engine a long time ago.

--
Moe

Buckda posted 06-03-2004 03:48 PM ET (US)     Profile for Buckda  Send Email to Buckda     
Tony -

Your Dodge does not run in Saltwater either. :-)

I think LHG has somewhere around 3000 hours on his twin 115's on his 18 Outrage....they don't work as hard as a pair compared to a single engine counterpart.

Also - motors need to be run...the storage over the winter is hard on them.

Just some thoughts....but really, I think that if you take very good care of your motor, you can probably get those kind of hours out of it....but after 3000, the motor doesn't really "owe" you anything.

Cheers,

Dave

elaelap posted 06-03-2004 04:01 PM ET (US)     Profile for elaelap  Send Email to elaelap     
Moe, the man...! And that's a great big DUH from me. Even with my (very) limited knowledge of things mechanical, I should have figured that out. I was expecting/hoping for a learned discussion about arcane forces acting on engine parts caused by the movement of the motor at sea, or at the very least an indictment of the harsh salt water environment. Oh well, now I've gotta come up with something else to take my mind off reality until it calms down a little out here and I can start putting those hours on my motor. Thanx.

Tony

elaelap posted 06-03-2004 04:21 PM ET (US)     Profile for elaelap  Send Email to elaelap     
Yeah, and thanks to the rest of you guys. That was too easy, even for me. I'll try to do better next time.
Plotman posted 06-03-2004 04:48 PM ET (US)     Profile for Plotman  Send Email to Plotman     
I'm willing to bet that one of the reasons that Larry has 3000 hours on the 115s on his 18 is that they just loaf along most of the time. That's 230 hp on a boat that 150 is the published max - my guess is that 3000 rpm is moving on that boat.

Think of engine life in terms of total # of revolutions - maybe even detonations (2x as many of those in a 2 stroke versus a 4 stroke).

That said, I would expect a lot more hours out of a 4 stroke than what we are used to getting out of 2 strokes.

David

gss036 posted 06-03-2004 05:04 PM ET (US)     Profile for gss036  Send Email to gss036     
The short and long of it that a boat motor is usually running with a heavy (full)load most all the time, that would be like hooking up your trailer or camper and find a hill w/15% incline and drive up it for 5000 hours. I just don't think too many engines would handle that. Maybe a Peter Built truck.
it is a whole different ball game for torque. Just like an electric motor running a watter pump, it may be rated for 11 AMPs but startup is , maybe 22 AMPS and it has to maintain that to pull or push the water load.
Hey! Nothing wrong with wishful thinking.
bsmotril posted 06-08-2004 11:45 AM ET (US)     Profile for bsmotril  Send Email to bsmotril     
Put your dodge in second gear, hitch up a 5000 lb trailer, and start towing up hill at 80% of the max RPM. Think it will still go 150 thousand miles of doing that continuously? That is the kind of load a boat engine sees versus an auto engine. It only takes about 8-12 horsepower to cruise at 55 mph in your car. The load on the motors and drivetrain is a lot different in the boat vs the vehicle.
BillS
JBCornwell posted 06-08-2004 12:08 PM ET (US)     Profile for JBCornwell  Send Email to JBCornwell     
I don't think 5,000 hours is an unreasonable expectation from a well maintained 4 stroke outboard running synthetic oil (I use Mobil 1).

Similar to nearly identical engines in commercial vehicles frequently exceed 300K miles. They get wrecked before the engines wear out.

Red sky at night. . .
JB

Bigshot posted 06-15-2004 11:13 AM ET (US)     Profile for Bigshot  Send Email to Bigshot     
Man 5k is easy compared to what I have seen in Central america. These commercial guys run conventional 2 strokes(OMC & Yamaha only) HARD every day, all day. I saw many from the mid 90's still going strong....had to have more than 5k on them, probably do that in 2-3 years.
dgoodhue posted 06-16-2004 10:47 AM ET (US)     Profile for dgoodhue  Send Email to dgoodhue     
My father got 5000 Hours out of his 175 Yahaha on his 22 foot Grady White. He uses his boat regulary duruing the summer months (teacher with the summer off) He had to buy a new one because Reverse failed and he couldn't get to shaft area to repair it because of corrosion. The motor still ran fine and was only off by 3-4 MPH on the top end when he bought it in 87. He had an 84 8hp Yamaha that had more hours on it as he used it pretty every day during the summer(as did my sister and I when were younger) but the mouting bracket corroded away. Motor ran fine. As you might imagine these are salt water boats...

My father is meticulous about his maintenance and storage, but he also believe that using the motor regularly helps its longevity.

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