gasoline marine engines

[tootalltony]

How many hours will a gas engine last for? before it needs to be re built?

[Lepke]

Hours depend on how it's used and how well it's maintained. Dirty oil and wot are probably the biggest killers. Steady cruising with good maintenance will probably give double the hours of the same engine in a car and about half the hours of what a diesel would do.

[a64pilot]

Usually somewhere between 500 and 5,000 hours depending on how it was run and how well it was cared for.
Some often die when the riser corroded through and fills the engine with water, but that kills its share of diesels too.

Look at yourself in the mirror and do an honest evaluation, if your mostly going to use the boat for a weekend beach house, vacation home etc., then you can save yourself loads of money by going with gas motors, but if you expect to really be moving most of the time and doing so for years, spend the bucks up front and buy Diesels.

Flip side of that, is that gas motors can be bought for a fraction of what diesels cost when it comes time to re power.

[a64pilot]

I disagree with outlasting car motors, they last almost forever if well cared for as they are run usually at low RPM and low loads.
Our Daughters 2010 Prius is over 250,000 and as it tracks average speed we know that it’s over 10,000 hours and burns zero oil.

Most gas power boats and I assume that’s what we are talking about here are planing hulls and that usually means they spend significant time on plane, and that’s usually over 4,000 RPM, and that’s screaming a V8 gas motor. Take your car put it in low gear and cruise at 4,000 or higher to see what I mean.

[tootalltony]

Originally Posted by a64pilot

Usually somewhere between 500 and 5,000 hours depending on how it was run and how well it was cared for.
Some often die when the riser corroded through and fills the engine with water, but that kills its share of diesels too.

Look at yourself in the mirror and do an honest evaluation, if your mostly going to use the boat for a weekend beach house, vacation home etc., then you can save yourself loads of money by going with gas motors, but if you expect to really be moving most of the time and doing so for years, spend the bucks up front and buy Diesels.

Flip side of that, is that gas motors can be bought for a fraction of what diesels cost when it comes time to re power.

This 7.4 gas engine is in a 22 yr old trawler owned by an older couple who were pretty easy on the engine .. They told me they ran the engine about 50 hrs each season-------so that's 1100 hrs minimum .
Could I expect to get 2000 hrs before it needs to be rebuilt?

[rslifkin]

A well maintained 454 with closed cooling will beak 2000 hours no problem. Usually they're killed by being run too hard or risers being neglected and failing.

3400 rpm is max continuous and it should turn 4200-4400 at WOT if propped correctly for most 454 variants.

I've got a pair of them in my boat. They've spent plenty of hours near max continuous up on plane. One has about 180 hours on it (got a long block after being murdered by an oil line failure before I had the boat), the other has about 1600 hours. The high hours one still has good compression, good oil pressure, runs great, only uses a hair of oil. Basically, it's still healthy with plenty of life left in it.

[tkeithlu]

2,000 hours is the expected life of a small aircraft engine, and they are air cooled and rather stressed. You can do much better than that.

Probably a better question than hours expected would be the condition of your motor. Cylinder compression is the simplist measure of engine condition. If the compression is up around 150 PSI and the cylinders are roughly equal, you're good to go.

You didn't ask about diesel alternatives, but they do have advantages if you have to re-engine. The fuel fumes are not explosive, and while diesel fuel costs are higher, for reason of the energy needed to break the chemical bonds you get twice the output per gallon. Today, an inboard gasoline engine is becoming a rarity on non-performance boats.

[thomm225]

Call Moyers Marine.

I'm betting they can give you a good (and correct) answer.

https://moyermarine.com/

[Jammer]

Originally Posted by tootalltony

How many hours will a gas engine last for? before it needs to be re built?

Depends on the engine. Depends on the boat, the installation, and how the engine is used.


I would say that, in terms of averages and round numbers, you could expect a 4 stroke gasoline inboard that is freshwater cooled, to last 20 years or around 4000 hours, whichever comes first. As pointed out upthread, higher performance engines that are mostly run at 60%+ of maximum output will not last that long.


4 stroke outboards, figure 2500 hours. 2 stroke engines, figure about half that.


Corrosion is the enemy of lightly used engines, especially ones that are raw water cooled and used in saltwater. Fuel systems problems are the enemy of engines that are hardly ever used or that are in storage.


Gasoline engines in weekender boats typically last the life of the boat; it's liveaboards, cruisers, and rental/resort operators that wear out motors.


In a sailboat you would almost certainly be looking at an Atomic 4, which is a topic in its own right.