How Many Hours on My Engine?

[JeffreyJoyal242]

hours and rpm are the answer. it used to be 500 hours and have rebuild. it really is the the rpm ,or work load of the engine. slow goers will grt five times that amount. big news, if she makes funny noises get it checked out.

[secondcurve]

How many hours can the average 4-stroke take before it needs to be rebuilt?

[Woodsy]

There is no such thing as average when it comes to boat motors. They are always under load/strain when in operation. It really boils down to maintenance and usage. Most boat motors are good for 500hrs or so, high performance motors can be considerably less than that. As a rule, I change my oil (synthetic) every 20-25 hours on both my engine and sterndrive... so far no issues. Got 350hours out of my last boat, the new one is just broken in with 100 hours.

Woodsy

[secondcurve]

Woodsy:

I hope that a properly cared for 4-stroke is good for more than 500 hours! God, I'll go broke if it isn't!

[Cal]

Most Merc non high performance engine , with the least bit of care should go 1000 hours with ease. High performance will be a lesser amount depending how hard you beat on them

[fatlazyless]

Engines are just like people. It's not the age, it's the condition. What's bad for engines is lack of use, and obvious things like never changing the oil or not using enough two-stroke oil. The $5.50 synthetics like Amsoil or Mobil One do a better job than the 1.09 Wal-Mart oil, Amen!

Mystery Oil in the gasoline is excellent for four stroke outboards and inboards and no good for two-stroke outboards but does not mix well with synthetic oils. Don't know why but was told that by a small engine repair expert. TechRon carb & injector cleaner, made by Chevron and very pricey, is great for cleaning out injectors, carburetors and gasoline filters and increases mileage.

[jceria]

One thing for sure.....
Constantly running at WOT (wide open throttle) will cut the enging life in half.

[MAXUM]

Originally Posted by fatlazyless

Engines are just like people. It's not the age, it's the condition. What's bad for engines is lack of use, and obvious things like never changing the oil or not using enough two-stroke oil. The $5.50 synthetics like Amsoil or Mobil One do a better job than the 1.09 Wal-Mart oil, Amen!

Mystery Oil in the gasoline is excellent for four stroke outboards and inboards and no good for two-stroke outboards but does not mix well with synthetic oils. Don't know why but was told that by a small engine repair expert. TechRon carb & injector cleaner, made by Chevron and very pricey, is great for cleaning out injectors, carburetors and gasoline filters and increases mileage.

Be SURE to check with the manufacturer before using synthetic oil in marine applications! I use Mobile 1 synthetic in everything I own with an engine except for the boat. I did some research on line and found out that Mercruiser (stern drives) very clearly state NOT to use synthetic or multi-weight oil. They do not specify why, but I found this which gives a pretty interesting reason why this is:

More recently, I have noticed that engines with roller lifters used in the pleasure-boat environment have exhibited undesirable wear patterns when synthetic oil is used. Specifically, because the oil is more "slippery," it appears that the rollers are sliding on the cam instead of rolling. This results in flat spots on the rollers and increased wear on the cam lobe. This problem only seems to present itself with lower valve-spring tension applications typically used with hydraulic roller cams. In race applications, with solid roller setups where 250 or more pounds of spring pressure exists when the valve is on the seat, there seems to be enough pressure to keep the roller on the lifter rolling on the cam instead of sliding.

Depending on your climate and the water temperature you typically operate your boat in, the viscosity of your oil should be selected accordingly. I believe that a straight grade SAE 40 oil is the most suitable for the majority of the performance marine engines. SAE 30 would be better for cooler climates. For extreme performance and supercharged engines, SAE 50 is suggested. Most synthetics are a multi-viscosity oil. Fuel dilution of the oil and contamination as a result of increased moisture in the crankcase seems to affect the multi-viscosity oils faster.

I've consulted more than one source to confirm not using synthetic oil or multiweight oils, so when I change the oil in the boat it's always fed SAE 40. This is by far the best explination I've seen so I thought it would be of interest. I did double check the Mercruiser web site and it shows that you can buy a synthetic blend. Normally I don't pay to much attention to manufacturer's recommendations, but when they specifically say not to do something, that tends to get my attention. Running a boat at WOT with a improperly matched prop pitch for the gear ratio can reduce engine life. It all depends on what RPM the engine is running in that condition. I personally very rarely run mine at WOT and not for very long.

[Weekend Pundit]

It is easy enough to add an hour meter, also called a Hobbes Meter by us aircraft pilot-types. There are stand-alone meters as well as those built into a tachometer.

Generally I will change the oil in the engine every 100 hours, assuming that I'm using it regularly (a few times a week), or more often if my boat is sitting idle most of the time (rarely!) or spending a lot of time motoring along at low speeds.

Fortunately for me, Volvo Penta thinks that synthetics are just fine for both my engine and stern drive. My 4.3L V6 has been run with synthetics for 13 years, still has great compression on all cylinders and the stern drive is still in great shape. About the only non-scheduled service I'm going to have to do at the end of the boating season is to rebuild the water pump...again. It's about the only part of the power train I've had any problems with.

[Dave R]

Originally Posted by Weekend Pundit

It is easy enough to add an hour meter, also called a Hobbes Meter by us aircraft pilot-types. There are stand-alone meters as well as those built into a tachometer.

Generally I will change the oil in the engine every 100 hours, assuming that I'm using it regularly (a few times a week), or more often if my boat is sitting idle most of the time (rarely!) or spending a lot of time motoring along at low speeds.

Fortunately for me, Volvo Penta thinks that synthetics are just fine for both my engine and stern drive. My 4.3L V6 has been run with synthetics for 13 years, still has great compression on all cylinders and the stern drive is still in great shape. About the only non-scheduled service I'm going to have to do at the end of the boating season is to rebuild the water pump...again. It's about the only part of the power train I've had any problems with.

and since VP and Merc use the exact same engines... I've been using Mobil 1 in all my engines, icluding those with roller cams, for years and years and the stuff is just fine. It's no more slippery than regular oil, it just has longer molecular chains that don't break down as easily as regular oil under shear stresses so it holds it's viscosity longer. It also flows better when cold and handles heat better. I run 5w-40 gold cap (the 15,000 mile change interval stuff) in my boat now.

[NightWing]

Not meaning to hijack this thread, but it evolved into a discussion about lubricants. Below is the Mercury link that discusses fuels and lubricants.

One item of importance in the oil section is a note saying not to use oils with solids in them. I know of one highly rated synthetic, special order in most places, that has molybdenum as an additive. Moly is an excellent lubricant but it is a solid and can "break out" of suspension under certain circumstances.

I have a new truck that I am running synthetic in and I chose a different brand that didn't have moly in it. Still special order, though.

http://www.mercurymarine.com/fueloil...mendation_faqs

[LIforrelaxin]

Originally Posted by Cal

depending how hard you beat on them

That is about the long and short of it as Cal says. I have a 30 year old outboard that just last year keeled over and died.....I have no idea how many hours but in the nieghborhood of 50 hours a year tells me better then 1500 hrs. and certianly it was not as powerful as it was in its youth but it still ran strong. Two things I think help as others have said proper maitanence, and not having a boat that is under powered. If the boat isn't powered properly you going to work the engine harder....and believe me there are a lot of under powered boats out there........... a second boat I know of (my uncles) had easily over 1000 hours on it and after a new carb. was put on ran the best it ever had...............

[Dave R]

Stress on the engine increases with the square of engine speed so running it at 5000 RPM creats 4 times the stress as 2500 RPM. I tend to stay under 3200 RPM with my engine as I've heard they last a long time that way.

The amount of hours on an engine are vastly less important than the condition of the engine. Passing a compression (or better yet a leak down) test and proven reliability are better indicators of the engine's expected performance and longevity.

[secondcurve]

Dave:

Thanks. I've been running my motor around 3800-4000 RPMs. I'll slow down a bit. I'm sure this advice will be as good as the advice you gave me on the chart plotter. It works great by the way.

[Dave R]

Originally Posted by secondcurve

Dave:

Thanks. I've been running my motor around 3800-4000 RPMs. I'll slow down a bit. I'm sure this advice will be as good as the advice you gave me on the chart plotter. It works great by the way.

My 3200 RPM rule was specific to the 7.4 MPI Mercruiser in my boat and is mostly due to the long stroke of the engine and utterly stock, GM-sourced, reciprocating mass. My redline is only 4600 RPM. Mercruiser also sold a different 7.4 liter engine, (the 454 MAG) that could be run at (or under) 3600 RPM for excellent longevity. It had a 5000 RPM redline, if memory serves. Merc beefed up much of the reciprocating mass in that engine to handle higher piston speeds. My point is that different engines are going to have different cruising RPM recommendations and 3200 RPM is not necessarily for all engines.

If memory serves, you have an outboard powered rig. 4000 RPM may be a perfectly acceptable (perhaps even low) operating RPM for you.

Glad to hear the chart plotter and Bizer C-map chart are working out well. I love having them aboard my own boat.

[NightWing]

When selecting an optimal RPM for sustained cruising, it is best to stay in a range where the boat is "on the step", with the least amount of wetted hull. Every boat has a planing speed that acomplishes the above. (Not including displacement hulls.) That speed is also when the powerplant is not working quite as hard. Once the boat is planed out with trim tabs and outdrive angle at efficient positions, the fuel efficiency is probably as good as you will get. Any more speed will just increase fuel consumption and engine wear.

[Dave R]

Originally Posted by NightWing

When selecting an optimal RPM for sustained cruising, it is best to stay in a range where the boat is "on the step", with the least amount of wetted hull. Every boat has a planing speed that acomplishes the above. (Not including displacement hulls.) That speed is also when the powerplant is not working quite as hard. Once the boat is planed out with trim tabs and outdrive angle at efficient positions, the fuel efficiency is probably as good as you will get. Any more speed will just increase fuel consumption and engine wear.

This is good advice. Some boats are so underpowered that this optimum hull efficiency speed can only be reached by really reving the heck out of the engine. Not a good thing for longevity.

Ideally, the optimum hull efficiency speed should fall close to the torque peak RPM of the engine, not the HP peak RPM. The torque peak of the engine is right where it has the best volumetric efficiency which means the intake system is operating at it's best at that engine speed and pumping losses are minimized.

[NightWing]

Originally Posted by Dave R

This is good advice. Some boats are so underpowered that this optimum hull efficiency speed can only be reached by really reving the heck out of the engine. Not a good thing for longevity.

Ideally, the optimum hull efficiency speed should fall close to the torque peak RPM of the engine, not the HP peak RPM. The torque peak of the engine is right where it has the best volumetric efficiency which means the intake system is operating at it's best at that engine speed and pumping losses are minimized.

That is a perfect example of why the selling dealer should prop the boat correctly. Ideally, WOT RPM should reach the engine manufacturer's spec with the boat geared for use.