How Long Will A Motor Last?

[riverrat]

Okay Mercury people,Donzi people,H.P.22.. :D
How many hours should I get out of my 350 mag/Alpha 1 setup? I got to thinking about this today as I checked out my hour meter, drinking beer. You know these types of questions come to mind.
81hrs. at mostly 5000 rpm. That's alotta r's already huh?
thanks, the rat..

[Sam]

If the oil and regular maintenance is done you can get several hundred hours before you need to start wondering. I have had as many as 900 hrs on a pair of of 454's with no sign of trouble. Hr meters are great but if you figure out how much time you speng idling and just putting around I bet you would be suprised at how many hard hours you actualy may have.

Sam

[HP 600SC]

Yes I agree.
Think if you had an hour meter on your car
how many would you crank up in a month.....
for me at least 80 per month and thats
conservative. Change that oil and use Mobil one!!! and dont forget the drive oil too!

[EricG]

FYI - My '88 350Mag/Alpha 1 has 530 Hrs....and still runnin' strong.....

EG

[Donzified]

1500 to 2000 hours is a good mark for a stock SBC. The more you hop it up and beat on it the shorter it lasts.
I get about 300 hrs per season,If i get 4 seasons out of it I am happy.
I only got 200 hrs out of one SBC took it back to the mechanic, his reply was "Your pushing about 450 hp, what did you expect,for about $2,000.00 I can get you going in about a month."I told him I needed 2000 hrs. not 200.
As you might expect I took it to some one else. As it turned out one of the hy.lifters wore through the bottom also wiping out the lobe on the cam. This was the result of the roller rocker bottoming out on the top of the valve keeper. You would think the @#$% mechanic would have noticed this when he built it.
I the quest of longevity I chose to step down the compresion, smaller cam, lighter valve springs,dual plane intake and a few other items that I'm sure I paid for but can't remember.I lost a little top end but she still has that "listen to me I'm not stock sound" I got about 600 hrs on it in 2 and 1/2 seasons, another 2 and I will be looking to rebuild again. Next time I will go roller cam also ,in the quest for a longer life.
Oil is alot cheaper then motors.


Keep your nose up.

[Dennis]

Hours and mileage can be compared to Hours x 100 = miles (ie: 81 hours x 100 = 8,100 miles. Sams example was 900hrs x 100 = 90,000 miles and still running? yep!!! Valves take a beating on marine engines and usually you need a valve grind or guides @ 1200 hrs and a rebuild 2 2000 HRS UNDER NORMAL LOADS (CRUISER) a compression test would say alot along with oil consumption or cylinder leak down. I run my X-18 HAAAARD !! I use Synthetic Oil and I do a compression test yearly so I can track DATA. That way I can spot a problem before it gets ugly.

[riverrat]

thanks guys, I was sure I would get years of service from this combo.. I talked to my engine builder buddy & he said what you say as well as adding the current 350 mag is one of the most reliable engines Mercury has out do to the fact that it's a low compression,roller cam motor. he thinks it will spin 5000 for a long,long time with no problem if I leave it alone. I.E. No procharger. Got to love these donzi's :D :D

[Digger]

interesting...any ideas on how long a stock 502/Bravo 1 setup would last? (with regular oil changes, etc?)

[Hardonzi]

I too run it at 5000 most of the time....Its a great motor,pushing my 22zx at 68mph with stock motor.Put open exhaust and you`ll think your in a APBA race..LUV IT :D :p :p

[Gearhead99]

I know I might be opening up a "HOT" topic here....But, I don't think a SBC or SBF can live for 1500-2000 hours running it hard as the average Donzi captain does.

Most Donzi's and tournament ski boats are worn down at 500-600 hours. They are breathing hard and have quite a bit of crankcase pressure. The high rpm, at extended running time is a killer.

Also, the temperture difference between the oil and the water causes rapid wear. The oil in boats runs very high, even with a cooler. While the water temp is usually very cold, 145 degrees. At that temp the engine doesn't burn [boil] off the impurites that are deposited in the oil. Hence rapid wear. The cold blast of water that comes in from the front of the engine makes the front cylinders cold and the rear so-so warm.

The oil pan has no air blowing around it to cool off the oil.

All factors in rapid wear.

My $.02

[CDMA]

Gearhead I agree. After 500 hours my engine is getting redone regardless of compression, oil use or anything. Fix it before it blows. It is cheaper in the long run.

Chris

[boldts]

I'll add .02 just to fuel your interest. I bought my 1969 Classic back in 1985. The first summer, my SBF dropped a valve seat and trashed the block. Since then, it's been the same engine and I'm no powder puff when it comes to enjoying my Donzi. She's been just about everywhere with me including ruff and smooth waters. Point is, if you take care of your engine, it will take care of you. Of course.... any help you can give it, the better the chances. By the way, I'm knocking on wood! ;)

[BigGrizzly]

Here you go. I closed cooling all my boats except the Criterion(the heat exchanger is on loan for race R&D).I run engine temps of 190F. this will extend the life of a engine at least 2 fold due to extra heat and a more even block temps. Marine engins run low t- stats to keep the exhaust cooler so salt doesn't cristalise. GM did a test years ago and found that a engine with a 160F t-stat sufferes 20% more whear then one with a 190F one. I have well over 500 hours on my 18 Corsican at some substained high RPMs. Ask anyone who has seen it or has ridden in it. Right Burtrum boy and Forrest.
my exhayst does run at a 140F due to the big heat exchanger.

Randy

[Formula Jr]

This is a tough audience for engine longevity. :)

Sometimes, I think you guys really should be building drag boats.

How long should an engine last.........ponder ponder.......
There's an easy answer and then there's a more involved answer. I'll just concentrate on the more involved answer.
Given, that you regularly maintain it stock with good stuff, an engine should last right up to the point that you have hour glassed the cylinders to such a degree that you start getting a lot of blowby through the rings. This is the normal, predictible, death of a well maintained piston engine. Which will happen between 1500 and 2000 hours as Donzified pointed out.

But that isn't what kills most engines that are cared for.
Alot of them never get there because one of the 200 or so important parts was tolerance mismatched when the engine was built, rebuilt or "Improved." That is something you have little control over, its all just luck of the draw and no amount of servicing will save you from that tick, tap or tock.
We deal with older boats and engines here in this classic donzi land. And the only way to get a rebuild that you know is proper is get one from the big boys, or known good shop, that happens to have that just right, over sized, crank bearing, or what ever. Joe rebuild isn't going to blue print the engine.

[BERTRAM BOY]

Absolutley Grizz,
I don't think anyone is harder on his engines than you are.....
BERTRAM BOY