How long will it last???????????

[donzi182003]

Hey guys I was hopin you all could give me a ballpark figure as to how long my 350 mag mpi is going to last. Obviously that is something difficult to predict but i am an outboard guy, I dont really know how many hours to expect out of an i/o. I cruise at 35-3700 rpm. WOT FOR NO MORE THAN 30 SECS AT A TIME AND FEW AND FAR IN BETWEEN AT THAT. I change oil every 35 hrs. ( Well it has 58 hours so once at ten hours, and once at 35:smile: .) I saw g-force 88's post and it got me thinking...... LEMME KNOW:confused:

[Rodger]

I put over 1000 hours on my turboed BBC. After all those hours the boat still would run with 2 or 3 MPH of the best it had ever done at low hours. My cruise RPM is about 800-900 lower than yours with the prop pitch I run. Otherwise, it seems we have a similar driving style. I don't change the oil as often as you, but I do run a 14 qt. pan and synthetic oil. When I had a SBC 400 in my 16' , I put about 500 hours on it. After that, I took the engine out and put it in my Chevelle and have been running it on the road for 12 years. All on the original build that I did in 1983. So, who knows? If you're lucky it may run almost forever, or until you feel like freshening it up. Good luck.

[Pismo]

Biggest deal will be salt or no salt. No salt and light use it can last thousands of hours and many, many years. My fresh water 305 Merc V8 ran alpha ran 3175 hours and 24 years without a rebuild, never opened up the engine at all. Lots of new accessories(starters/alternators/trim pump) but the long block, manifolds, carb, distributor were original. I did not even chage the original water pump impeller for 21 years and over 3000 hours. I ran this boat very hard for many of the years, lots of skiing, towing, it completely sank twice, and I never touched the engine---Why?-- Fresh water.........Open cooling salt water would have been a whole different story. The boats was falling apart by the end when I sold it but the engine was still strong.

So enjoy for many years or get a closed cooling system. If you are used to outboards you will be very happy with the longevity of an i/o.

[Donzigo]

Having had a boat for 35 years, (10 of them), I would advise that under ordinary use, such as the use you describe, you should expect an engine life of around 1,500, before a rebuild or replacement. To extend engine life, one must keep it maintained and flushed for 10 full minutes with salt away or 1/2 cup of Joy, etc, to get the salt out. I respectfully disagree with the "salt will eat up you engine quickly" theory as related in the above post. IMHO, it is engine "use" often that makes the difference. There are guys out there, who use these V-8's to pull parachute riders everyday, in the salt, who never flush their engines. Rare, yes, but they can get 2,500 to 3,000 hours of use, simply because the salt does not stay in the engine and corrode the iron. My conclusion is that salt alone does not destroy the engine. Having said all that, I much prefer, have had, and will repower my present twin 454's with FWC, when the time comes. It is far better to run in salt with FWC, no arguement from me on that. My present 454's have 500 salt water hours, since install in 1997. I challenge anyone to find a speck of rust on them. They are pristine; because, I flush them for 10 full minutes each, after each use. They've never spent a night with salt left in them. I have through-hull pick-ups that allow me to close the salt off and flush, if I spend the night away and in the water.

[Rootsy]

take care of it... proper maintenance when required, change the oil at regular intervals depending upon severity of use, use quality lubricants and make sure you warm the motor up to operating temperature before you go boating (ie idling til up to temp at dock)... build a bit of oil temperature before you hammer on it (idle out of the harbor).... and if in salt flush it properly and it should last indefinitely for you...

last sbf (351W) that i saw opened up (and it wasn't stock) that had been treated like this since new, religiously... with 107,000 miles on it... didn't so much as have a ridge above the pistons... reason for failing performance was eroding valve and seat faces and valve guide seals... a true testament to treating a motor correctly and the longevity you can aquire...

Jamie

[Pismo]

My point is that in fresh water a new merc motor will last a very, very long time with little work, you will probably get sick of the boat or it will fall apart before you need to replace the engine. This is absolutely not true in open cooling salt water without significant added work such as "flushing for ten minutes after each use", draining, or replacing manifolds regularly, etc. Enjoy

[MOP]

Having been a salt water marine mechanic for nearly 40 years I have to put my 2 cents in, I am now a boat broker and find many 20-25 year old salt cooled engines still doing a good job for there owners. True risers die an early death usually about 4 years on dry stack or trailered boats, manifolds usually last a couple of more seasons. I have seen many get 6-7 years out of risers on boats left in the water as their stuff stays wet I like most change both at the same time, engines last a long time. The big thing with salt water in an engine is to keep the iron wet, if left to dry corrosion sets it real quick you can ruin a block in a about two weeks. A point about iron and salt, I have a friend that does serious ship wreck diving and recovery of artifacts. He raised the cannon off the British war ship Collodion it went down off Montauk Point in the 1600's, the cannons when raised were immersed in fresh water that was changed regularly based on salinity. The cannons are now on display and look damn near new. So those that say iron will rot in salt are only partially right, as of late but most will not admit there is a bigger and bigger problem with electrolysis in fresh water. Now you ask why I brought that up!!! Well knowing a fair bit about the subject and having learned much in schools over the years it is proven that much of the internal and external damage is caused by electrolysis and leads to corrosion. Point I ran my 16 in salt for 2 seasons my drive was pristine and well cared for, then went up to the pure fresh water of the 1000 Islands. I and many other experienced pitting of our drives, I spent three days sanding and touching it up when I got back. On my last trip up I carefully cleaned my zincs and only got a few pits, mind you I got no more pitting when back in salt for many hours. So in closing my ramblings it all adds up to care and maintenance, flush ,wash, and spray anything that can rust with a preventative of you choice and enjoy your Donzi Daze!

Phil

[mattyboy]

RIDE HER TIL SHE BREAKS
FIX HER AND RIDE HER SOME MORE.

yes all the above posts are true proper maint. and good care will prolong engine life
but to me worrying about if your powerplant will fail takes all fun out of having a boat, we all know ( knock wood, rubbing my rabbit's foot, throwing salt over my shoulder,step on crack break your Mother's back) we are one ride from the big one, you could have a brandy new motor and have a oil pump or oil line fail
pic up an obstruction and over heat, and the comet hailbop could fracture and a piece blast right thru your hull :tongue: and sink to the bottom ;)

check everything before you leave, watch your gauges, and check everything when you get back and enjoy your boat when it runs :)

[donzi182003]

:biggrin: WHAT A RELIEF!!!!! I was not expecting to hear such high numbers. I flush my motor for not only ten but 15 minutes each time. Sometimes I swear i burn more gas flushing than I do running around all day!:tongue: I always let the engine heat up to running temp before planing. Can anyone give me ideas as to putting soap in the flusher??? I have used a bottle of miracle gro up to now. Its been effective. Maybe another board member has a revolutionary idea that has not been shared.

Thanks guys,
Ed

[MOP]

Can anyone give me ideas as to putting soap in the flusher???

Yes real simple! Go to your local garden shop and buy an inexpensive inline water hose fertilizer/insecticde injector, make a short jumper hose an put it inline on your water hose and WaLa. I get two flushes out of a filling running a full 20 minutes, I figure it coats an extra 50-60 cents per flush.

Phil

[Donzigo]

......all good rsponses. Pismo, I agree with you. Sorry, if i sounded otherwise. MOP, great posts. MOP, I've never had exhaust mainifolds last over 4 years....risers either.

Madpoodle says he uses the Miricle Grow bottle, I beleive. I have a trhu-hull water pick-up that is TEE-D with a hose coming up to the back firewall, so that I can sit in the back seat and flush easily. Others have used the window cleaning spray bottle to administer soap detergent, salt away, etc.

I think the 10 minute (AT IDLE ONLY) rule applys well. I hear my neighbors racing their engines on a hose. Remember that the hose only delivers a small amount of water in comparisison the the water in the lake/ocean. When you race the engine at idle, you burn things up like impellers.

.....may I have more posts, please. I'm , learning a lot here.

[donzi182003]

MOP,



50-60 CENTS A FLUSH?!!! I CANT AFFORD THAT! :cool: NAH IM JUST KIDDIN THATS THE LEAST YOU CAN SPEND TO PROTECT A MUCH BIGGER INVESTMENT. I USE THE MIRACLE GRO BOTTLE AND ITS BEEN GOOD TO ME. DO YOU ALL FLUSH IT WITH FRESH WATER NO SOAP WHEN YOU ARE DONE OR YOU LEAVE SOAPY WATER IN THERE? I TRY TO FLUSH THE SOAP OUT. I AGREE WITH DONZIGO, IF YOU RACE THE MOTOR IM SURE THAT IT WILL REQUIRE MORE THAN WHAT THE HOSE IS PUSHING OUT.

ED

[JimG]

I leave the soap in, figure it lubes the impeller some. I crank my motor with the kill switch pulled to build 40 lbs of oil pressure before starting, so I guess the soap helps there...