cracked block or cracked head?

the small crack is right next to either the first spark plug or the last i dont know what order they go in on the driver side right under the valve cover.can i weld?

i think its the head.

Pop a set of rebuilt heads on it. They don't cost that much and only take a 4-5 hours to change.

if the crack is below right below the valve cover then the head is your culprit.

Swapping heads is not too bad, however I am personally a fan of junk yard motors. Chevy truck 350's are a dime a dozen (Fords too for that matter), you can probably get one delivered on a pallet to your doorstep for less than $500. Were talking milkshake for oil right? No telling how long the previous owner ran it with water in the oil if that's the case. There is a good chance that your main bearings are shot if he put any time on it while the oil pump was pumping water to them.

There are some guys that will post replies that the truck motor is not the same, makes less power, etc. Your boat is light, a 250 hp motor should work just fine. If it were mine it would be getting a junkie long block.

(Message edited by mikeski on December 10, 2005)

No, no water in the oil yet. Can i just replace the head and inspect for further damage?

You should replace both heads, or at least have the other head resurfaced and a valve job so both sides are performing at the same level.

How many hours are on your motor?

490

That's equal to about 50,000 miles give or take. I would pop a set of new or rebuilt heads on and go. Like I said about 4-5 hours and you should be done not a hard job.

How much to have a shop do it?

YOU CAN DO IT !!!!! If I had to guess I would say about a $1,000 in just labor. There are plenty of people that can walk you threw it on this web-site. Just do a little at a time in the evenings and don't rush it. It's a perfect project for the winter.

now should I replace both or just the bad one?

REPLACE BOTH!!!!!! Replacing one would be like going to the shoe store and buying one new shoe. I would do a basic tune-up after putting the heads on.

10-4

is this the same boat with the rotted floors? if so, ouch.

Best deal on heads I have found.

http://www.race-dezert.com/cgi-bin/trader/atl.cgi?ct=2&md=second&id=2902

The last time I had to swap heads was on my 1998 Jeep Grand Cherokee 5.9L (special HO edition). They have notoriously weak valve seats and I had a ended up with a burnt valve. Since it is a common motor I found a good set at a local junkyard. With a 90 day guarantee I bought them for $220 and swapped them out in one afternoon.

It's a much easier job on your boat. It's a more common head casting too. Find a good local Ford or Chevy junkyard (which ever motor you have), take them down, match them up. They should guarantee them for at least 90 days so you may want to wait to spring if you can't put the boat in the water now. I would guess that you could do it in less than 10 hours for less than $500. You bought a 14 year old boat, it's going to need work and it's best if you do it yourself. Find some local guys that can help you along.

There may a difference between the springs on a road motor and a marine motor - the springs are much harder to avoid valve float. Marine motors operate at much higher rpms and lower temps than road motors. On some motors, the valves are different as well - alloy formulation. Several rebuild companies offer marine heads for about the same price as road engines. Inquire about it.

Generator duty motors generally use the same head springs as marine.

I am concerned as to how the head was cracked. This is generally not something that just happens as a result of normal wear and tear, something caused this to happen. Heads generally crack from being overheated, which could have been the result of a single case where the cooling system failed or it could be the result of prolonged high RPM, lean fuel mixture, excessive pinging, etc.

The crack may be the tip of an iceberg, there may be much more extensive damage inside. Cracked pistons, scored cylinder walls, burnt valves, etc.

For sure you should replace the head, don't try to weld it up or patch it. If it is cracked to the point that it is visibly leaking water externally then it probably has additional crack lines internally that will cause even greater problems.

Before you remove anything run a compression test on all cylinders. Remove the other head and have it inspected. Carefully inspect the cylinder walls to see if there is any scoring, an indication of a broken ring.

If you buy junkyard heads you might want to consider taking them straight to a machine shop and having them "rebuilt": new guides, valve stem seals and the valves lapped. This will assure that you have an engine that runs good for a long time and doesn't burn oil.

Right on guys thanks for all your support.

Have you run the motor if so how did it run? The reason I ask is this if it does run and run's smooth no knocking ect. I would just slap a new or rebuilt set of heads on. I personally would not put a used set of heads there are to many what if's. With new heads on it if the rest of the motor turns out bad pull the new heads and bolt them on a new short block. Like Rod said check every thing real well. A cracked head like that is not normal. It could be that the motor had water in it during the winter and cracked the head.

right on, I just got a quote from marine center for 8 hrs labor and the price of two heads should i just have them do it cause bro i know nothing at all about machanics it like jiberish to me bro. So for a grand im all good. But yeah the boat ran sweet for about 4 hours on sat.

That's good that it ran sweet. you should be fine with just a set of heads. I would talk to the machanic at the marine center and ask if he would do it at you're house as a side job. you might be able to save $$$$$$$$.

right no doubht thats exactly what he said is hes going to investagate all but aviously replace as little as possible. He said more than likely just heads.

When you get a chance let's see some pic's !!

Don't fire the engine with fresh heads before going over the cooling system completely. As somebody else said, something cause that cylinder head to crack, and overheating would be my first suspicion. You're pumping water out of the crack, so the cooling system is compromised, even though you are not seeing water in the oil. I have see temp gauges give a false reading because the probe on the sending unit is not submerged in coolant. Check everything in the cooling system, from the raw water p/u on through the entire system. If everything is good, then perhaps you just had a cylinder head fail, although it is not a common problem on the 351w Ford. And it is good advice to do them both while your there. I'd stick a fresh set of lifters in there since you will be staring at them when the intake manifold and heads are off.
And, speaking of manifolds..if you are considering a High-perf. intake manifold for the engine, now is the time as well....

Aaron, what's the equasion you're using to come up with 490 hrs equals 50,00 miles? Just curious because I come up with 14,700 miles at an average boat speed on 30 mph. Sorry for the Hijac.

I thought every 100 hrs was equal to about 10,000 miles. Boat speed is about 30mph at the same time look at the beating it's getting with all the stop and start's and add on average 2000 pounds of ballast. Just my thought's or is that wrong?

Im trying to upload the pics but it keeps saying the size needs to be 1000x1000 or something. by the way did i ever tell you guys what i got this showroom floor beauty(minus the cracked head and rootedply) for? The guy was askink$8500.00 for it and i had two seadoos on craigs list aking$7500.00 with the added coment i dont need money just want a boat so the deal was on. He dug the skis and of course i was diggin the boat so good is good. then the problems set in but my positive money margine is still tippin the scales if i can upload the pics youll see what i mean.;

Not sure myself Aaron. I think it's harder on the drivetrain to transfer power to the pavement than it is in water. I'm quite sure these boat engines, even heavily weighted can knock down 2000 to 2500+ hours if you do two things: change oil very frequently and keep it running cool.

I agree with you on that sparky! I'm not sure about the hour thing either. You are wright on the milage if you put it on paper according by normal driving in a car. I just thought the weight and also the fact of such a higher rpm. my boat run's at about 3000 rpm for 30mph. In a car 3000 rpm is haulin some a$$.

True, but what speed do you do most of your boating at? My boat only does thirty when cruising back and forth from riding spots un-wheighted. When riding weighted at 24 mph, my boat tachs about 2600. Again, sorry for the HJ.
Eric, post those pics so we can see what you're talking about.

dude im trying can i e-mail them to you

The water is much much more demanding on the drivetrain. It's equivalent to going up a steep hill in a car 100% of the time.

Maybe untill it gets on plane, but after that I disagree.

WAREK1814@AIM.COM Try that and let's see what happen's.

Eric I got the pics. That boat does not look bad at all. A sampson tower on it would be off the hook! No money out of pocket for that boat just two jet-ski's. I would of done that even with the few minor problem's you're havig. Keep us updated on it! GOOD LUCK

Interesting, it's seems like common sense that boat motors work harder (regardless of being on plane or not). I have really never had anybody challenge the notion. If it were an easier environment on the engine I don't know why all the manufacturers beef up the internals?

I would agree that 2,500 hours with good maintenance is easily attainable. Under simalar maintenance conditions a truck with a similar motor should run 250,000+ miles.

hijack off/debate on

if water wasnt so demanding you wouldnt need 400hp engines on boats

The internals are no different than what goes in street driven vehicles. The long blocks come off the same assembly line. Manufactuers' just "marinize" them. And who needs 400 hp. Most comp boats have between 275 and 330. Where do you get 400?

Let me rephrase my statement. The marinizers use engines off the same assembly line except that the cranks and bearings are of a heavier duty variety, similar to general use engines like pump motors etc.

To the point about horsepower, it's less about one peak power rating and more about a broad and tall torque curve that has the capability of turning that screw under the water.

From a load standpoint a boat offers greater resistance to movement than a car so it's more demanding the engine. This is basic physics issue not my opinion.

I can tow my boat across the pavement with my truck, I cannot tow my truck across the water with my boat.

I have seen the insides of both marinized and automotive based 350 CID Chevrolet Engines, and they looked the same to me.
Back when Chevrolet was offering a steel crank in 3.48 stroke, many of the marine engine suppliers were specifying that unit with the 4-bolt main blocks. When the steel crank option went away, the cast cranks were all that was available.
If you call an aftermarket supplier and ask for a crank for a 350 Chevrolet for a marine application, you will have the options of some mods to journal design, and the option of steel over cast, the same as an autmotive application.
Chevrolet did offer a different oil pan /pump/pickup assembly for the marine long blocks designed to minimize windage and pump starvation. The rod/main bearings were generally the same, as far as I know.
In the big blocks, the 454/7.4 blocks with the casting "High Performance" on the right rear of the block behind the flexplate designates a 4-bolt main block. They came in trucks, generally 1 tons. I have seen them in boats, but I have also seen 2-bolt blocks in both trucks and boats.

I will side with Mikeski on the wear debate.
Cars have a multi-geared transmission, which keeps the engine operating in the most efficent range, and at an RPM where wear is minimized.
Most boats do not have luxury of a multi geared trans. The prop configuration is our only way to multiply torque. With the exception of boats like my buddies 23ft Beisemeyer Daycrusier with the 454/Turbo400 combo, to go faster or pull a larger load at a given speed, us boat types pretty much just have the throttle to push.

Bearings, pistons, rings, valves, valve springs, guides, lifters; everything in any given engine that is moving and is subject to wear is also subject to a finite number of engine revolutions before that wear takes place.
Running an engine in an automobile going down a highway in high gear turning it 2000 RPM, with a minimal load and power demand on it for two hours is far different than running your boat engine at 3500-4000 RPM for the same given time, right? I think that it is safe to say that the majority of boats engines run at higher sustained RPM than car engines.
More cycles of the reciprocating assembly can only equal more wear. I just don't see any way around it, but that is just my opinion.

Would yuo rather buy a car that was driven 50,000 miles at 60mph (like a boat) or one that has beendriven 50,000 miles in town? All car manufacturers have reduced maintince for highway driving IE consistant rpm. I believe that it is the varying rpms that do more wear. also the car has to switch over and become an pump during decell and cars have to deal with a lot more tempature changes. The trans on a car provides a direct link to the road most times (yes todays auto trans lock the torque converter in as low as 2nd gear)not so with my boat the prop can "freewheel" decreasing the startup load on the engine,like capicator start on a electric motor.

wear is not only related to high rpms.
For example a boat running 3000-3500rpm with no ballast does not have the same wear as some that does.
metals wear less while planning at 3500rpm than they would if you cruised your boat all around the lake at 2000 with the stern sitted deep in the water. (dunno the expresion in english)

I think the maint. reqirement differences for city vs. highway driving are more related to lubrication contamination associated with stop/start driving and opertaing an engiine that is not fully warmed-up than varing the RPMs.
Load on the crankshaft is a factor, no doubt, which, again, is minimized by the torque multiplication effect of a multi-geared trans. Obviously, differences in weight and where in the rpm range a given engine is operated are realistic considerations.
I can tell you this, the supplier my machine shop uses for extreme-high performance valve springs and other components rates their life in wear cycles, which is directly related to how long the engine runs at a given RPM. When my last sprint-car style motor was built, the life span was directly correlated to the rev-limiter. Lower RPM equaled longer engine life, and higher RPM equaled less life.
This, as I said, is just my opinion, but it has worked for me on more than one $12k plus engine, and the guys dumping 40k into 850HP alcohol burning 430 inch engines use the same rule of thumb..

For a car I agree indeed, but for a boat is more complicated, under that idea a boat using a high pitch propeller planning at 2000RPM would last forever, and it does not because it put loads of pressure on other parts besides pistons, like crankshaft and bearings. Temps go higher inside the engine and that wears it all.

This thread is dead and way off base!!!! Start a new one.