Rule of thumb for engine hours, servicing, etc

OK, I will jump in where the wise among us rightly know better than to tread … this is, after all, a gentlemanly forum and I probably won’t get kicked too hard and my critics will add valuable information for you.

1. I am asking in the venue that that all else being equal, e.g. no deliberate abuse, and engines serviced when required

Therein lies the first problem. You will be very lucky to find two boats with equal hours that also have the same maintenance and usage history. Boats that tend to get more use tend to be better cared for and may be in much better condition.

2. I see many posts when looking through the ads about low hours typically, just what is low hours

How long is a string? Certain types of boats tend to be used in similar ways in similar places for similar periods. You could draw a parallel with cars, you might expect a certain make and model and year vehicle to have a certain mileage range that is considered “typical.” Anything less is low mileage and anything more is high mileage. In most cases the mileage and hours is not what really matters but the condition under which the mileage and hours were obtained.

A low hour boat might have been “rode hard and put away wet” by an owner who ran it at max continuous power every minute he used it and rarely changed the oil or gave much thought to how it was warmed up or cooled down. He might not even know if the cooling system has a zinc or two in the coolers. A high time engine might have been treated like a family heirloom and meticulously maintained by a savvy owner who likes machinery more than fishing or drinking.

3. I see posts about manifold replaced at xxx hours, just what is being stated here. I understand that typically there is a external manifold of some type over the engine manifold used for cooling which will corrode away eventually or something to this effect

The term manifold in this usage refers to a double-walled part of the exhaust system that takes exhaust gases from the cylinders and directs them to another part of the system where water is injected to cool the gases before being directed overboard. The water used for cooling the manifold is “raw water,” that is the water in which the boat floats, salt or fresh depending on where the boat is used. The internal section of the exhaust manifold can get quite hot in use and when it is cooled with seawater, salt can corrode the metal quickly. Depending on local salinity, how hot the engine was when it was shut down, and if it was flushed with freshwater before storage, manifold life can vary widely.

4. Just how is a fresh water cooled engine set up doe sit have dual manifolds, one which has outside lake/sea water pumped through to cool an internal closed fresh water system. Something like a radiator (outside water) to cool a radiator (inside closed loop system) is antifreeze involved with this type system?

You pretty much got it correct. Most cooling systems use a “raw water” pump to push seawater or lake water through the tubes of a heat exchanger. Engine coolant with antifreeze (for corrosion control) circulates through the engine just like in your car. The raw water picks up heat from the engine coolant just like the air going through your car radiator, then goes on to cool the exhaust manifolds before being sprayed into the exhaust gas to cool and quiet it before going overboard.

5. I see comments about engine overhauled at xxx hours, what does this mean? I would certainly hope that the engine is not completely pulled out of the boat and rebuilt with just lets say with only maybe 200 hours.

More boat engines probably rot away from disuse or fail from misuse than hours of usage. If the boat was commercially operated it may have reached its normal overhaul period but unless it was raced, that number should be far greater than 200 hours. There was some kind of damage that led to such an early overhaul unless the boat sat unused for many years in poor storage conditions.

6. How would this compare to an auto engine which may go 100,000 miles

We don’t have enough room on this board to go into that one … besides, I have my limits.

7. Another item I see often is many ads which proclaim low hours, example 450 hours in two different ads for the same make and style of boat. Yet the in the ads both boats look like identical twins, yet one maybe asking $70,000.00 and the other is asking $119,000.00 what as a guess would be the reason for such a disparity?

Refer to answers 1 through 5. Depends on the previous owner’s interest, the size of his checking account, and how the boat was used. The cheap one might be overpriced and the expensive one might be a steal. As much as I am skeptical about small boat surveyors - OK, surveyors in general, hire one and look, listen, and ask questions, thousands of questions.

Good luck, it really is fun but it ain’t for the faint of heart!

A few words on the smaller Sea Rays:
1) The 28 through 34 are good boats. The 28 is the entry into the twin screw (albeit I/O's). They are excellent boats and can take way more than you can. They're fast (26kts or so) and ecconomical. There have been a few brain problems , but on a boat more than 2 years old that should have been addressed. If you're into fishing or a little rougher water the 29 Amber Jack is a bit heavier and slower, but excellant.
2) The 31 is not one of the more popular models as there is also a 32 which I seem to recall seeing with straight inboards as well as I/o's (which may account for some of those price differences).
3) The 34 is a great family cruiser, the start of the serious boats, runs straight inboards (Z-drives). Not as fast as the others, but a way more comfortable cruiser. She also burns a bit more fuel.
4) On the 28 expect to see about 200 hours per year, working down to 100 for the 34.
5) You'll find few if any fresh water cooled motors until the 34. I'd look for a fresh water run boat or at least a northern boat. That florida salt is death.

After 1,000 hours you're bound to be looking at a repower or at least major rebuild. 3 to 4 years for risers and manifolds in salt water.
If you're new to boating I'd recommend about a 3 year old 28. She's solid, comfortable, good handling, easily maintained and a great boat to learn on. Expect to have her 2 years before you trade up unless most of your boating is on the inside in which case she may be around for awhile.
Have the boat surveyed and the motors pressure tested and checked over. Money well spent. Look for a clean bilge. A dirty one is a sure sign of a badly maintained boat.

"2000, 31 yesterday here which is fresh water cooled, 175 hours". Personally I would stay away from that 31. Way too few hours for one thing (if it seems too good....), and again the 31 was not a good seller because it was the same engine package as the 28, but a bigger boat, still with the I/O's which made it a bit of a beast to dock (too much windage, too little prop too far back), and slower that the 28. If you need size go for the 32 or 34, otherwise stick with the 28 (stay away from the single I/O 26 and below with cabin). 454's have been around forever. Great motors, but they've been tweaking the electronics to improve efficiency which always brings on weird problems. I recently was to give a lesson on one and couldn't start it for anything. Truly felt stupid until a mechanic advised me that if the voltage was down even .2 it was a no go. No starter click, no battery winddown, nothing. It was as if the kill switch were pulled.

2000 is kind of old. Don't be afraid to be a hard ass bargainer. There are a lot more boats in this size range out there than buyers. Hit 20 guys with rediculously low-ball numbers. One of them will bite or at least have a real good counter. Good Luck.

What is low hours?
Well if you figure that most deisel engine manufactures recomend overhaul some where around 10 to 12 thousand hours, that gives you an idea...

Hi,

Here is a quick rule of thumb on engine hours vs rebuild.

Have the engine completely surveyed prior to purchase, this is especially important if the maintenance records are not fully filled out or are non existent. Make sure you get a lube oil analysis as a part of any engine survey ( any surveyor worth his time and money will do this as a normal procedure or have an approved engine tech do it for him)

If the engine comes back as within manufacturers limits for blowby,( this indicates worn rings and or excess exhaust back pressure and can be easily identified by an oil analysis/crankcase pressure check) oil consumption, power developed then you are probably good to go with moderate cruising plans for a small boat like you describe.

As long as you are aware of what you are doing with the boat and keep an eye on oil burn etc you can probably go safely past the manufacturers rebuild times as you will not suffer a catastrophic failure by doing so but will be aware of the true condition by monitoring the test results from Oil and Coolant condition and not letting these get too far out of spec you will be ok.

Regular tests of Lube Oil are an absolute must of any scheduled maintenance program and these should be shortened to a calendar date rather than a hours run if the hours are run, most manufacturers also have a max limit on the months between service regardless of the hours run.

Good advice from K1W1. You won't find maintenance records on boats like these though except at the marina that does the work. The rebuilds should come at aprox: top end 300 to 500 hours or 3 to 5 years ; total 600 to 1,000 hours or 5 to 7 years. A boat that's run upwards of 250 hours per year will probably do better because it's probably run by someone who knows and maintains more.. Unlike a diesel it is doubtful that you can ever do a 2nd rebuild, but you won't get into diesel until minimum 34' w/ SR, and most likely 38 or 40 plus it's way more $. Not for the newbie.