-
Now i know this has been discussed before but im still a little shaddy....What is the diffrence?? I could maybe see a diffrence in an off shore racer or something else along those lines, but for us jet boats that dont sit in the water for whole seasons (mostly on the trailer), most not used in salt water, ect. What could be the diffrence? People have said to me "a car/truck engine was not made to be ran at at such a high RPM(5000) for such a long time". I'm only looking for about 400HP (+-50) from a 460.
[ August 14, 2002, 05:39 PM: Message edited by: AntRant ]
-
Marine motors usually make torque and HP at lower RPM since there is no transmission(most of the time!) to help it get up to speed. Also, boats have more of a constant load requiring different HP and torque curves. Running at a high RPM for long periods of time has the same affect in both applications - drastically shorter engine life!
Many people use car/truck motors and seem happy. But there is always a performance upgrade to be had with a marine motor - like stronger out-of-hole. The biggest difference is the cam specs.
-
From what guys have told me in the past the main difference in a marine motor is usually the steel crank. The marine cam is going to be better suited for a boat too. I've been running a stock olds out of a Toronado for 4 years with no problem. Of course I'm not getting over 50 mph either! :D
-
mainly cams and on some engines the clearances are a little looser to allow for the added stress and high rpm use.I have ran a car motor in my boat fora while with no probs when i had my last crank turned i had the machinist to add a little more clearance(towards the upper end instead of the tighter side).
-
A big concern with car engines in boats is piston to cylinder wall clearance. Boats generally require a "looser" fit because of lower water/coolant temps and higher oil temp. Expansion rates are different than that in a car. A few engine builders have warned of "sticking" a piston in a cylinder, though I have yet to hear of this happening.
-
So if i was to take a stock car or truck motor that runs good and doesn't need a rebuild right now, I should change the cam and intake for better torque? Anythong else? What would you guys do?
-
AntRant:
So if i was to take a stock car or truck motor that runs good and doesn't need a rebuild right now, I should change the cam and intake for better torque? Anythong else? What would you guys do?Install brass freeze plugs.
Use a larger oil pan.
-
Mercury, Indmar, Marine Power and all of the other engine suppliers all buy there engines from GM by the box car. To the best of my knowledge there are no special mods to the engine in terms of clearances or camshafts.Now this is not to say that some marine suppliers wil not make mods but if you buy a 454 with a carb your are buying the same engine that you would find in your Crew cab.Freeze plugs in most cases are changed to brass and if the heads are removed for upgrades a good marine head gasket will be installed. Other than these changes for the most part these are the way they come from GM GREG
-
AntRant:
So if i was to take a stock car or truck motor that runs good and doesn't need a rebuild right now, I should change the cam and intake for better torque? Anythong else? What would you guys do?Converting a vehicle motor to marine use also involves changing out the starter and alternator. Marine starters and alternators are sealed to prevent moisture and gas fumes from getting in and sparks from getting out. Automotive starters and alternators are not.
