Why do I/O's have short engine life?

[RickJ6956]

Re: Why do I/O's have short engine life?

Car engines have a thermostat that keeps them the same temp all the time. I don't think I/0's have one, and if they do, they're not as efficient as a car's thermostat in maintaining temp.

Boat inboard engines (shaft and I/O) do indeed have thermostats, typically set to open at 140 to 160 degrees. The fuel system is tuned to burn clean at those temps. A close eye on the temp gauge will show that the thermostat cycles fairly quickly as it opens to allow cold water in, then closes to maintain engine temp. Mine typically drop 5 degrees or so, then recover.

Also, compared to cars, boat engines' exhaust manifolds are usually very thick, heavy cast iron which also helps to smooth out the temperature fluctuations.

 

[jmarty10]

Re: Why do I/O's have short engine life?

I have a newer i/o 4.3l merc. I do an oil and filter change (along with all other required maintenance) at end of year. I also do a mid season (25 hrs) oil and filter change during the summer. This responses here is dead on. Your motor is pushing a 3,000 lb + boat and sometimes pulls skiers, tubers etc... That motor is working. But, changing the engine oil and filter is a cheap maint item that would seem to give more longevity to a boat motor.

Also, I think winterization here is key. Could I do an engine oil change, gear lube change, engine fog, stabil the gas, change the water seperator and........... drain the engine block? Yes. Do I? No. I dont do this because I am not a professional. Especially, draining the block and adding antifreeze correctly (correctly being the key word) Why would I want to risk damaging my engine when a prof mechanic can do all of this for $150. Hopefully, all of this maintenace will avoid an expensive engine overhaul.

 

[Loco-Coco]

Re: Why do I/O's have short engine life?

Car engines are not the same as boat engines. A 4.3 in a Jimmy is NOT the same as a 4.3 Mercruiser. One major difference is the higher nickel content in the blocks of marine engines. They're built stronger. Period.

Do some searching around on the net to find threads about people installing car engines in their boats. I remember one thread where a guy replaced his boat's 4-cyl Ford with the "identical" automotive version from a Taurus. He said the Taurus engine was like new and had something like 45K miles on it. The engine lasted one season in his boat and at the end had next to no compression.

On the flip-side, the drag racing car guys commonly build marine engines (350s, 454s) as they can get a lot more power out of them while retaining more reliability than any automotive engine.

My '79 F150 4X4 351W with all stock running gear, 3100 RPM at 62 MPH. Has been doing that for all its life.

Load your box up with bricks, tow your boat, and keep the truck at 62 mph going up a never-ending steep hill. That's what a boat endures. How long would your 351 last?

Another similar comparison is between motorcycles and snowmachines. 2-stroke bikes could hit 50,000 miles before rebuilding. 2-stroke sleds will go 6,000 miles before needing a rebuild. Same engines. Difference is motorcycles coast, run with little load and have gearboxes. Snowmachines stop FAST without throttle, are always under load and have centrifugal clutches (for all intents and purposes the same result as a boat).




LC.

 

[mtrainTurbo]

Re: Why do I/O's have short engine life?

In my experience, boat engines die because they are owned by idiots.

After working in the industry and shopping the used boat market, I am blown away at the number of abject morons who thought boat ownership was a great idea.

Lack of maintenance, lack of use, poor winterization/frozen blocks, poor maintenance, inappropriate (AUTOMOTIVE) replacement parts, etc.

One boat I looked at was owned by guy of foriegn descent who tried to tell me his boat had special oil in it. When I pulled the dipstick, it was sky BLEEPing blue. He then showed me that his "special oil" was 2 cycle engine oil. He then slapped the dash and said (in the thickest accent ever) "good BLEEPing boat! You buy?"

Or the other guy who ran his boat - in a winterized state, with the plugs out - for 2 hours trolling, engine steaming and engine compartment filling up the entire time.

Or the third boat I looked at, who's owner bought the boat and then failed to register it. All the titles were missing. The boat was a mid 80s Volvo powered boat with the nicest new SP drive I had ever seen. 4 years later, the boat was un-saleable. It had to be cut up because no paper trail could be established to re-register it.

In short, the engine isn't the problem, its the nut who owns it.

 

[Lyle29464]

Re: Why do I/O's have short engine life?

Car engines are not the same as boat engines. A 4.3 in a Jimmy is NOT the same as a 4.3 Mercruiser. One major difference is the higher nickel content in the blocks of marine engines. They're built stronger. Period.




Everyone must be in a nice mood today to let this slide.

 

[a70eliminator]

Re: Why do I/O's have short engine life?

lol no sense in beating a dead horse..

 

[45Auto]

Re: Why do I/O's have short engine life?

Car engines are not the same as boat engines. A 4.3 in a Jimmy is NOT the same as a 4.3 Mercruiser. One major difference is the higher nickel content in the blocks of marine engines. They're built stronger. Period.

Everyone must be in a nice mood today to let this slide.

If he's not willing to do the little bit of research it would take him to learn the truth, no sense in anybody wasting their time on him ......

 

[dannyual767]

Re: Why do I/O's have short engine life?

When I read Loco's post, my blood pressure started to go up and I knew that I had to raise the BS flag. It looks like several of you guys beat me to it.

posted by Loco,

On the flip-side, the drag racing car guys commonly build marine engines (350s, 454s) as they can get a lot more power out of them while retaining more reliability than any automotive engine.

Dude! Get real .

 

[H20Rat]

Re: Why do I/O's have short engine life?

Another similar comparison is between motorcycles and snowmachines. 2-stroke bikes could hit 50,000 miles before rebuilding. 2-stroke sleds will go 6,000 miles before needing a rebuild. Same engines. Difference is motorcycles coast, run with little load and have gearboxes. Snowmachines stop FAST without throttle, are always under load and have centrifugal clutches (for all intents and purposes the same result as a boat).

6000 miles on a snowmobile engine? i wish! i've got my AC 600 EFI engine on the bench right now. Piston broke at 3k miles, spewed chunks. Its simply amazing that you can have an engine that puts out over 100 hp, and I have absolutely no problems lifting it. It is relatively tiny!

In my defense, its rare to get 50k out of a 2 stroke motorcycle, but in general they do obviously last longer.

 

[Loco-Coco]

Re: Why do I/O's have short engine life?

Sorry, didn't mean to rub anyone the wrong way. After re-reading my post, I understand why I did. I did a lot of reading last night and confirmed some of my thoughts as well as disproved some of them.

Where I should have went is that a 4.3 removed from a Jimmy and placed in a boat as-is will not give the same service as a marine 4.3 (without considering blowing up the boat from spark, and not considering the poor performance from the different cams). Is this correct or not?

A friend of the family did exactly that and replaced his boat's 4.3 with one from a car. Got a year out of it and it was pooched.

Another thread I came across (not sure what site), guy replaced his 4-cyl Ford with a low-mileage one out of a Taurus. Again, he got one season out of it. Could there be enough corrosion of the frost plugs, water pump, head gasket in just one season to kill the engine? (new in spring, dead in fall).

Do marine engines have forged cranks instead of cast? I've read that they did but have not read that they didn't.

LC.

 

[jmarty10]

Re: Why do I/O's have short engine life?

Here is one that defies some of the logic here. Guy at work has a 20 year old starcraft, 18 footer. Takes it to the lake once per year, has it tuned before he goes, uses it on his week vacation, puts it in storage for rest of year. Only problem now is dry rotting floor. So who knows............

 

[mnypitboat]

Re: Why do I/O's have short engine life?

Here is one that defies some of the logic here. Guy at work has a 20 year old starcraft, 18 footer. Takes it to the lake once per year, has it tuned before he goes, uses it on his week vacation, puts it in storage for rest of year. Only problem now is dry rotting floor. So who knows............

Well if he stores it correctly, then has the same people that stored it prep it every for him, then they probably fix whatever is wrong with it and he just strokes a check. I know plenty of people like this.

 

[skargo]

Re: Why do I/O's have short engine life?

I'm looking at 10-15 year old runabouts and I'm amazed at how many have new or rebuilt engines, usually a 4.3L v6.

Given that in a car, that same engine should last 100,000 miles, or 1500 hours, easily (with only minor maintenance) why do these engines typically last less than 500 hours in a boat? Is it the high rpms and rapid acceleration that ski boat engines are exposed to?

Dave

My boat is an I/O and is 32 years old. It still has the original 5.7 in it, it is factory fresh water cooled.

 

[sbbamafan]

Re: Why do I/O's have short engine life?

Mine is almost 20 with 1300 hours on it. Runs perfect!

 

[Friscoboater]

Re: Why do I/O's have short engine life?

Most of time it is from someone not winterizing.

 

[steddy]

Re: Why do I/O's have short engine life?

Look at cars. Around here (Michigan - rust from road salt in winter), if a car's engine needs rebuilding, the rest of the car is usually pretty much shot. Scrap the whole thing out. In a boat, the engine might be the only thing wrong with it. The fiberglass doesn't rust out like a car's body. Re-build the boat's engine because the rest of the boat is still good.
I also agree with the maintenance (or lack thereof) issues. Take care of it & don't beat on it; it will last a lot longer.
Put a car's engine through the same torment & neglect as a marine engine and see how long it lasts. Neglect will kill anything though.

 

[Fishing56]

Re: Why do I/O's have short engine life?

Have a 4.3lx 1996 Mariah alpha one. Change oil regulary. Has 450 hours on it. It is trailered and garage kept. Runs perfectly, even no problems with trim system yet.

Fishing56

 

[2000silvers2k]

Re: Why do I/O's have short engine life?

6000 miles on a snowmobile engine? i wish! i've got my AC 600 EFI engine on the bench right now. Piston broke at 3k miles, spewed chunks. Its simply amazing that you can have an engine that puts out over 100 hp, and I have absolutely no problems lifting it. It is relatively tiny!

In my defense, its rare to get 50k out of a 2 stroke motorcycle, but in general they do obviously last longer.

I know this is unrelated to the post, but i have a 99 AC zr 600 efi, with over 6k miles on the engine, never had a rebuild or any serious engine work, knock on wood.

 

[Fordiesel69]

Re: Why do I/O's have short engine life?

The V8's really do not hold up to the high RPMS like the I4 and I6's do. The engines usually got cracked from lack of winterizing. Even a good boater can get a family emergency, or a family member gets sick and forgets all about the boat as more important things are taking place.

Also lack of maintence is the big one as others stated.

 

[MPII]

Re: Why do I/O's have short engine life?

I think the majority of the issue is proper care. But also, think of how much resistance a boat motor is under each time in use. A 4.3 GM block can get a chevy Camaro above 100 with no problem. In a boat, 45? 50 at most? Constant pressure.