Boat motors, wear and tear = an Interesting 1/2 truth

[vegasphotoman]

I call this a half truth because some boats are ran more than others in a season, same goes for cars, so I based these numbers on a typical user.
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Consider a sameple = 1996 boat/motor (compared to a 1996 car/motor)

BOAT
10 summer trips to the lake each season, times x 13 seasons = 130 x 3 hours run time per trip = 390 hours on motor or thereabouts (probably less!) 390 hours x 30 mph if you took that motor and put it into a car and miles = 11,700 equivelent miles ...very low by car standards!

no wonder my 4 cyl mercruiser 3.0 looked brand new inside when I pulled the valve cover off!

CAR
13 years x 12,000 miles average per yr = 156,000 miles, at average speed of 30mph, 156k divided by 30 = 5,200 hours! of wear Car motors see more than 10 time more wear than a boat motor sees!

=====================what did I get from calculating this?

Age of the motor on boats is much less important than how it was treated for those hours of runtime......

Boat motors seem like a great place to get a clean used long block for your next budget car project!

 

[werthert]

Re: Boat motors, wear and tear = an Interesting 1/2 truth

Isn't there usually a lot more stress put on boat motors though?

 

[Bob_VT]

Re: Boat motors, wear and tear = an Interesting 1/2 truth

Only one thing to factor in....... most boats are run WOT or at least 3/4 rpm. In a car you rarely use the upper half of the rpm range.

a simple 5 hrs on a car vs 5 hrs on a boat engine and the boat engine saw more severe use. Which burned more fuel in 5 hrs?

Now..... proper maintenance will allow the boat to last as long as the car and visa versa. I have a 1966 outboard that runs like a watch a 1969 the same way.

 

[86 century]

Re: Boat motors, wear and tear = an Interesting 1/2 truth

It not how much they run but how they are run. I have the 5.7l chevy in my truck and one boat the truck will run all day at 1800rpm at 70mph and never get over half throttle my boat however runs 50mph at 4100rpm wide open. The reason a auto eng will not live in a boat.

 

[lucky logger]

Re: Boat motors, wear and tear = an Interesting 1/2 truth

the way i have always thought about it is a boat in a way is always going up hill there for it is working hard no mater what rpm it ia at

 

[vegasphotoman]

Re: Boat motors, wear and tear = an Interesting 1/2 truth

It not how much they run but how they are run. I have the 5.7l chevy in my truck and one boat the truck will run all day at 1800rpm at 70mph and never get over half throttle my boat however runs 50mph at 4100rpm wide open. The reason a auto eng will not live in a boat.

86 Century...I would have to disagree with ya a bit,on that part of your reply, especially bigger v8 boat motors = chevy 350s /454BB/ ford 302s and 460s and such are used commonplace in boating. They are "marinized" by adding water headers/water exhaust manifolds, low temp 145deg tstats and special tstat housings, water intakes and petcock valves etc, the internals are "car" stuff (block/piston and rods/intake)


I do agree with ya BobVT

Everyone has a good point on the "harder working motor", especially the going uphill comment is a good way to explain it, it is a bigger load boating, than a car on flat ground.. good call all....

I would assume more load = more bearing wear and cylinder wall wear...but 10 times less overall usage has to be worth something.....

.....and Im thinking one oil change per year, at the least, 30 hours boating per season (eng run time) 30hrs x 30mph average = 900 miles car equivalent usage per season / between oil changes, so oil changes are 3 to 4 times more frequent than cars. That should be worth something (clean oil all the time)

....on the other hand not everyone guns thier boat wot all the time (but I do, for sure!!) I do when going across the lake, the other 1/2 time Im 2500 rpms or less tubing or cruising etc

I wonder how much of a positive/negative effect, running at a lower engine temperature AND frequent oil changes, has on wear and tear???????????

 

[scoutabout]

Re: Boat motors, wear and tear = an Interesting 1/2 truth

Doesn't the valve gear, springs, cam , etc. get a beefing up for the constant high-rpm marine duty?

 

[superpop]

Re: Boat motors, wear and tear = an Interesting 1/2 truth

I have heard that a running the motor at the lower temp is actually harder on the motor because the fuel burn isn't as efficient. That is why most car motors run at around 180 degrees or so. I think what is the hardest on a boat motor is the constant high RPM operation. Most V-8 motors are really not designed to operate at 4000 RPM's for extended periods of time, thus the transmission in a car keeps the average RPM's down under 2500 most of the time. My other reservation about using a marine motor in a car would be the condition of the cooling jackets in the motor. Most motors are raw water cooled so corrosion can be an issue. With a car motor this is typically not the case as the AF typically prevents this. I think the common factor for both is maintenance, I know guys that have cracked open a properly maintained 302 Small Block and it looked and performed like new, compression was great. But that was after a lot of use, but it was babied. I think it is the same with Boat motors, you get clowns that never change the oil because they only used it for 40 hours in a season and they forget about the moisture buildup and breakdown of the oil over time. Lubrication suffers and bearings and rings start to wear and then you run it hard at 4500 RPM for 1 hour straight and stuff wears faster.

 

[H20Rat]

Re: Boat motors, wear and tear = an Interesting 1/2 truth

rpm's make very little difference in the wear of an engine, so comparing that is useless. What DOES make the difference is the load factor. The load on an engine can be calculated with a formula involving the fuel consumption, rpm, and amount of air going in, but generally, the higher the load, the higher the wear and shorter life. Boat engines are under high load all the time!

And yes, engines that are designed to run at a high load factor (boat engines, generators, industrical applications...) have quite a few differences than engines designed to only see those high loads occasionally.

 

[sly_karma]

Re: Boat motors, wear and tear = an Interesting 1/2 truth

OK, now consider outboards. Still run full throttle but designed for marine use and all that entails. How do you factor that in?

 

[JoLin]

Re: Boat motors, wear and tear = an Interesting 1/2 truth

Doesn't the valve gear, springs, cam , etc. get a beefing up for the constant high-rpm marine duty?

No. Volvo-Penta and Mercruiser use stock GM blocks and heads. The only thing that might be different (not positive) is the valve cam profile. Otherwise it's just a car engine with different gaskets and externals.

Crusader (inboard powerplants) is known for using super-duty GM motors (with 4-bolt mains and such). The "performance" after markerket re-power outfits can sell you whatever you want.

 

[a70eliminator]

Re: Boat motors, wear and tear = an Interesting 1/2 truth

I have to disagree about operating RPM not being a factor because every revolution of the crank contributes to wear, I agree load is a major factor.

 

[45Auto]

Re: Boat motors, wear and tear = an Interesting 1/2 truth

If you want to compare automotive wear to boat wear, you need to apply the same load to both engines.

Take your new car and attach a big metal plate to the back bumper with a tow chain so the car has to drag it down the road. Now start piling cement blocks on the plate till your car only gets about 4 MPG. You car is now seeing about the same amount of drag your boat is operating against all the time. You'll also find that your car is only capable of 30-50 MPH (depending on engine) at WOT with this load.

Now you can compare wear based on hours of operation. See how long your new car motor lasts.

 

[vegasphotoman]

Re: Boat motors, wear and tear = an Interesting 1/2 truth

I agree with Jolin that they are reg blocks, but that the cam profiles are designed for higher rpm power and lots of torque

Superpop has a good point about the rust issues with raw water.......


I know my mercruiser 3.0L 4cylinder still had cylinder wall crosshatching when I did the headgasket a week ago....and it is a 19 year old motor....wont see that in a 19 year old car truck eng, it would be like glass in the cyl, highly polished and worn. also there wasnt much in the way at all of carbon build up on the pistons or cyl head dome/valve faces.......

I have seen 3/4 thick carbon buildups on the backside faces of valves (cars trucks)....can you imagine the inefficiency of all that carbon blocking the airflow, soaking up fuel and weighing the valve down

Its all food for thought!

 

[vegasphotoman]

Re: Boat motors, wear and tear = an Interesting 1/2 truth

If you want to compare automotive wear to boat wear, you need to apply the same load to both engines.
Take your new car and attach a big metal plate to the back bumper with a tow chain so the car has to drag it down the road. Now start piling cement blocks on the plate till your car only gets about 4 MPG. You car is now seeing about the same amount of drag your boat is operating against all the time. You'll also find that your car is only capable of 30-50 MPH (depending on engine) with this load.
Now you can compare wear based on hours of operation. See how long your new car motor lasts.

Actually, my 2007 F150 super crew 4dr only got 12mpg city at average of 1500 rpms, if I shifted it into LOW gear it would run high rpms at about a max speed of ...well heck it was a $35k truck so I didnt max it out in low ever, but you can imagine only 40 or 50 at best mph.....and I would hazard a guess that WOULD beat up the motor........WHHHAAAAA high rpm and give it real bad mileage, might even put it down to 4mpg

boats are Geared 2rpm engine = 1 rpm prop....

whereas cars are geared a bit higher for efficiency......?? you would have to factor eng rpms / tranmission gear ratio / rear axle gear ratio to get a real comparision to a boat with its simple 2 to 1 ratio etc

 

[86 century]

Re: Boat motors, wear and tear = an Interesting 1/2 truth

The merc v8's well chevy anyway have steel crankshafts and are better balanced than auto eng. Before new cranks got cheap ten years ago we used boat cranks in high hp v8's.

 

[QC]

Re: Boat motors, wear and tear = an Interesting 1/2 truth

I agree with Jolin that they are reg blocks, but that the cam profiles are designed for higher rpm power and lots of torque

Actually the cam profiles are designed for relatively low RPM and to prevent reversion (water sucked back into cylinders). This is why high performance, high RPM cams are not recommended (or used) for most marine applications. The exception is dry stack headers for drag boats etc.

FWIW, with the exception of 45, what all of these posts have started to point to, but have not quite got there, is that neither hours nor miles are good indicators of engine longevity or maintenance intervals.

An example is a truck that averages 45 MPH over it's life might make it 600,000 miles between overhauls, maybe more. But a refuse truck that averages 6 MPH might not make it to 100,000. So maintaining them at the same mileage intervals would be stupid right? Some "professionals" do though

The best equalizer is probably gallons of fuel consumed as that is indicative of the amount of work that an engine has done. And when you think about it, that is its job and that is its only purpose . . . work. It neither knows, nor cares how far or how long it works only the total amount of work . . . which is directly related to the amount of . . . fuel.

Still not perfect, and nothing is. Cold starts, thermo cycling, transient loading, deep lugs (not necessarily bad), high RPM operation, ignition timing, fuel quality, air cleanliness, emission levels, technology, cost, assembly tolerances, supplier quality, materials (see cost), bad operators, poor maintenance etc. etc. etc. all play roles in determining this

 

[45Auto]

Re: Boat motors, wear and tear = an Interesting 1/2 truth

you would have to factor eng rpms / tranmission gear ratio / rear axle gear ratio to get a real comparision to a boat with its simple 2 to 1 ratio etc

Totally false. Load is load.

An engine turning 4800 RPM and putting out 300 HP has no idea what's bolted to the back of it. It could be in a boat with 2:1 gears, or trying to move a loaded truck in 4WD low. All it knows it that it is turning 4800 RPM and pumping the required amount of fuel and air to make 300 HP.

QC has the best take on it. The amount of WORK an engine does is going to be directly related to wear.

The merc v8's well chevy anyway have steel crankshafts and are better balanced than auto eng.

Nope. Check the part numbers. You'll find that they are identical.

 

[Silvertip]

Re: Boat motors, wear and tear = an Interesting 1/2 truth

The verdict is still out on whether four stroke outboards will last as long as their two stroke counterparts. Two stroke motors are all ball and roller bearing supported in the crank and connecting rods so they can sustain high rpm much better than the insert type bearings in a four stroke. As for the 4 cylinder, six cylinder, v6 and v8 engines in boats, they are indeed auto variants but the marine cam profiles are very much like a truck engine and thus are limited to the 4600 - 4800 RPM range in stock form. In the case of the 3.0 Mercruiser that motor was never offered in a car but it is a derivative the 4 cylinder Chevy engine of years gone by. 50 MPH in a boat requires something in excess of 4000 - 4500 RPM from the engine. 50 MPH in in my truck is about 1600. It takes about 15 - 20 HP to maintain 50 MPH with a car if you ignore any head wind, soft tires, etc. It takes perhaps 80% of the boat engines power just to get on-plane and probably 95% to maintain 45 - 50 MPH. So in one mile the boat engine is not only operating under more stress, it is reving nearly three times as fast as the car engine. Engine temperatures in a car/truck run at 195 degrees these days primarily because they have pressurized cooling systems and can safely run up to 240 degrees for a short period without damage provided the coolant mix is proper. Older boats had raw water cooling and open cooling systems so it was essential to keep temps low. The is an adage that says "boat engines don't die, their owners kill them!" Install a vacuum gauge on your boat and keep engine vacuum at 8 - 9 inches or more and the engine will provide optimum service. The same holds true with a car or truck. Engine vacuum and rpm are two key factors in how the ECM on vehicles are able to get the mileage they do these days.

 

[vegasphotoman]

Re: Boat motors, wear and tear = an Interesting 1/2 truth

Good points and info Silvertip!!!!!!!!!!!!

Either way it all makes for good banter, AND we can all learn something from each other...YEA!

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PS my Dad claims, when he was growing up in Detroit in the 50s, they would get USED TEST motors from the car manufacturers for cheap, and they got one that had a full ROLLER BEARING CRANK assy........

(Roller cranks as mentioned by Silvertip in the 2 stroke comment)
that car engine would be a rare and interesting motor to check out I bet! mebbe worth a decent pile of cash too