gas engine life span

[tootalltony]

I am looking at a Bayliner 2859 with a 7.4 gas engine. How many hours will a gas engine like this last before it needs to be re built?
Tony Smith

[ranger58sb]

Can't really say, Tony... and a lot depends on where it's been used and how it's been treated. And somewhat on whether it's raw water cooled or freshwater (anti-freeze) cooled.

I've seen guys say 1000 hours... and other guys say 2000 hours... and other guys say even longer.

That's still includes replacing risers, manifolds etc. periodically, especially in salt water...

It's not uncommon to do a compression test (cited in a purchase contract) while you're in the buying phase. That at least can give you a clue bout what condition an engine might be in on that particular day in time.

-Chris

[tootalltony]

Originally Posted by ranger42c

Can't really say, Tony... and a lot depends on where it's been used and how it's been treated. And somewhat on whether it's raw water cooled or freshwater (anti-freeze) cooled.

I've seen guys say 1000 hours... and other guys say 2000 hours... and other guys say even longer.

That's still includes replacing risers, manifolds etc. periodically, especially in salt water...

It's not uncommon to do a compression test (cited in a purchase contract) while you're in the buying phase. That at least can give you a clue bout what condition an engine might be in on that particular day in time.

-Chris

This boat has always been in fresh water (Lake Champlain)....It is raw water cooled and the seller tells me everything on the boat has been maintained to the highest standards (yeh right, they all say that)
The surveyor tells me that he can tell from a sea trial if the compression is an issue

[Tetepare]

Originally Posted by tootalltony

The surveyor tells me that he can tell from a sea trial if the compression is an issue

Rubbish. Granted, motor people can detect things like one cylinder totally shot, but nobody can tell if a couple are a bit low and headed south.

That’s why pro motor people use compression testers.

[Stewie12]

Definitely a compression test and have the gearbox/clutch looked at as well. A good owner will have an engine log book and record the amount of oil required each time the engine is checked and the hours. That will tell you a lot.

[ol1970]

I’m approaching 800 hours on my 7.2L Ilmor, knock on wood, but it’s been rock solid and I’m counting on another 1000 hours before a major overhaul. If not, oh well time to go boat shopping! Actually that’s honestly the plan is about when this craps out it will coincide with us switching from steam to sails for a while.

[foufou]

with this type of question the answer is always, it depends. But an example of what is possible is a small pickup truck gas engine I own. It has 400,000 miles. so at an average speed of 40 MPH that is equal to 10,000 hours. That is is not unusual for a gas engine but YMMV. And in addition to a compression test you might consider an oil analysis which can reveal more about the state of engine wear. Best wishes

[vpbarkley]

Marine service is much harder than road service. Road engines are fully loaded when accelerating hard or when pulling up a long hill loaded 100%. Marine engines are fully loaded.

[LooseGoose]

Get a real marine mechanic to do a proper engine survey. Getting this wrong is a high 5 figure mistake. Marine gas engines in a planing powerboat last about 3,000 hours when well maintained. They work very hard, like driving a loaded dump truck uphill, all day long.

[a64pilot]

Originally Posted by Tetepare

Rubbish. Granted, motor people can detect things like one cylinder totally shot, but nobody can tell if a couple are a bit low and headed south.

That’s why pro motor people use compression testers.

No, I disagree.
A motor that’s down on compression will most likely burn oil visibly and won’t make full power / RPM.
A compression tester most often comes into play once a problem is suspected in an attempt to determine if there are cylinder issues.
Even then a compression test isn’t really a very informative test, you don’t do a compression test on an aircraft engine for its annual inspection, you do a leak down test.

Not to be disrespectful, but on a Bayliner I’d be more worried about the boat than the engines.
As with everything there were some good Bayliners, but I have no idea which ones are.