Auto engine marinization

Hi, I have 28ft sport cruising boat Sidra 28 GTO with 2 OMC 5,0 L (ford 302) V8 engines and Cobra stern drives. Now I want to replace engines with 2 GM 6,2 diesel Chevy V8 and I need help. If someone have information what and where to order for marinisation. Please help me, I am in Croatia-Europe and have no experience with GM engines. Mail me on bimex@zg.htnet.hr

 

It is an incorrect comparison between a race car and a planing boat. Cars do not run at maximum torque load like a boat. This produces higher combustion chamber pressure and temperature. Also, the load curve to put a boat up on plane is different from the one to accelerate a car. Graphite race head gaskets will create violent galvanic corrosion that will shorten the life of the engine and drive.

 

Try Lancing Marine in the UK

http://www.lancingmarine.com

 

In one way... marine engines are remarkably like car engines.... they share lots of parts... If you were to check a lot of "high performance" offshore engines.. you will find that most of them use aftermarket Generation IV Chev blocks 9.8 inches from centerline of the crank to deck height... or 10.2 ( tall block)... Most of these are either Chevorlet "bow tie" blocks... or from an aftermarket manufacturer like Dart or World Industries, ( Merlin )... Most of the time the water pump is removed and a "sea pump" with a rubber impellar is installed.Sometimes the factory water pump is left in place for circulation. But whether you are using a "closed" cooling system with a heat exchanger.... or an "open" cooling system that uses the raw water from what the boat is floating on...you must have a "sea strainer". Some of the internal problems incurred because of the high load factor of a boat application is oil cooling...plus, because of the constant higher combustion chamber temps.. it is advised that inconel exhaust valves be used... especially if you are planning on supercharging the engine, and Stainless intake valves. There are plenty of manufacturers of water cooled exhaust manifolds. Some people prefer the nice shiny stainless tubular versions.. some like the cast versions. The biggest problem I've seen with raw water cooled offshore engines is they run too cool... if you are running is salt water.. you don't want the temps any higher than 150. If you are running a heat exchanger.. then you can run more normal temps like 180 degrees. My understanding is hot salt water can be very corrosive. Much more than cool salt water. I ran raw water cooling on my boat... and it is understood that the blocks and heads were disolving and would eventually need to be replaced. Besides the brass core plugs.. you should install zinc sacrificial anodes in the water system... If you really aren't familiar with marine engines.. you are just building yourself a lot of problems. I've seen so called "experts" cobble together some real disasters.Even Mercruiser has had problems with their propulsion units... they have been mating big 502 cubic inch engines to whimpy Bravo outdrives with cone clutches.. If you were to go to offshore boating forums... you would see how many people are moaning about toasted bravo drives.. So... even the people that are building marine power plants for public consumption are having fits. So... even a properly "marinized" automobile engine isn't without it's problems. I think most people with high performance auto engines that have been converted only expect about 300 to 500 hrs before they are worn out and need serious attention. It has been theorized that a new expensive offshore boat can cost upwards of $2,000.00 dollars an HOUR to operate... Especially at today's fuel costs... My boat had twin 540 cu in Blown Chev engines and when "cruising" at 60 mph... they consumed about 80 gallons per hour... and when you really started working the "sticks" it would go over 100 gallons per hour... but... at 100 mph on the ocean... you couldn't run that fast for long... you would get too tired hanging on....

 

maybe it is the best vay for me to buy original marine diesel engines! There is so many informations against marinisation of Chevy 6,2 engines. Also may be problem with rotation- one engine left and secon right rotate becouse of OMC Cobra stern drive.
Thank you for your ansver
Boris

 

thank you very much

 

I have a similiar question; I just blewout the head gasket in my 1989 Mastercraft Tristar. This is a competition ski boat with a Inmar Ford 351 Windsor engine. Pulled off the heads and found they were corroded thru to the water jacket; my case is probably so corroded that it needs to be replaced. Did I mention the previous owner had the boat in salt water for 7 years before I bought it????

I am planning on purchasing a reman marine long block and stripping mine down to the core. The 'new' engine will cost me $1,600 plus all the other assorted parts and gaskets I will need. I could get a 351 short block from a local salvage dealer and remanufactured heads, replace the freeze plugs with brass and put my old carb, exhaust, starter, etc on it alot cheaper. I also have to change the cam out due to the marine engine is LH turn. Is there anything else I need to change? This post talked about alot of things such as pistons, etc. that are different. I just need to know what parts are different inside the engine.

 

How hard do you plan on running your boat? If it is a ski boat... probably not as hard as an offshore high speed boat. I'd suggest since the boat already has a marinized Windsor.. just get a used block and heads... take them to a reputable engine rebuilder. Play mix and match with the "marine" parts from your old engine such as the cam, since it is reverse rotation.. the rest is a lot more simple than starting over with a clean sheet of paper.. you already have the marine reverse starter and charging system. The big difference in the internals might be better pistons and oiling system... When an engine runs under a constant load... the pistons and valves run hotter... so don't skimp on good pistons and valves. I'm sure you can get some aftermarket forged pistons and better quality valves...I know J and E forged pistons are about $1,000 for a set of 8 . I'd go with the inconel exhaust and stainless intake valves for longevity. Go with a "high flow" oil pump to ensure good oiling of the internals... People think that high pressure means high flow... not always... some marine engine builders like to have bearings on the "loose" side of tolerances so that more oil splashes up on the cylinder walls to aid upper cylinder lubrication. ( Since the engine rarely gets the high manifold vacuum during deceleration like an auto engine ) there is less oil sucked up past the rings and onto the upper cylinder walls. Run a good quality 10-40 oil ( not straight weight ) because you want the flow past the bearings as much as oil on the bearings themselves. This is one of the biggest problems I find boat owners do is run too thick of an oil and starve the upper cylinder areas of lubrication.I'm sure you already know about brass core plugs in the block and "marine" head gaskets.

 

It Is Easy

I have been using auto engines in boats for years.Forget all the mumbo jumbo,this is how I do it.This may sound crude to the people who preach new stuff but here goes.I usually try to find a rusty pickup or car with V8 that runs good(it is easy here on the coast),use model before computers.Then remove engine ,change freeze plugs,get your water cooled exhaust manifolds.Install engine and hook up raw water cooling and go.I use the same distributor that was in vehicle.changing carb and fuel pump is up to you ,I never do.Also a 2bbl carb will work fine.
I have been putting engines in boats I built for 24 years just like I described.Don`t worry about salt water and raw water cooling,rusting out the block is an old wives tale,my engines have always been in salt water with no problems.
I am sure this post will get a lot of flack,but the joke is on them,because this works and is inexpensive.

 

couldnt get my head to fit the shirt

 

Woody: an automotive distributor is not spark protected. You have been lucky not to have an explosion. The moving parts of a marinized engine are different from an automotive. You may be running a low performance boat. In a planing hull the low end torque requirements are higher than for a car. If you don't change the camshaft the boat will be a pig. Also, blocks in salt water rust. It is a proven fact. If you use automotive head gaskets with steel inserts they will rust through first. You also don't change the carburator, starter or alternator. It may be cheaper but also foolish and illegal.

 

Dang Woody.... sounds like the way to go.... until the hull burns to the water line because of a leaking fuel pump and a little spark from the starter or alternator or distributor.... It's not anything that you could sell to someone.
I don't think there is a single manufacturer of an auto engine later than 1980 that doesn't have a computer of some sort on the engine management. 1983 was the last year for a car or light truck with a carb.. So... you must be putting in some old stuff....

 

Engines

If The Engine Is Pre 79 Advance The Cam Timing 2deg With A 3 Position Timing Chain Set.after 79 The Cams Were Retarted To Meet Nox Limits For Emissions.so In A Engine After 79 Advance The Cam 4 Deg.any More Than This Can Cause Valve Clearance Problems.retard The Ign Timing Total To No More Than 38 Deg If Comp Ratio Is Below 9.5 To One.also Do Not Use Vac Advance.the Water Pump Needs To Be Underdriven Or The Bearings Will Wear Premature.if A Marine Water Pump Is Avail Use This Instead Because It Has Bigger Bearings And A Stainless Impeller.a Flame Arrester Must Be Used And The Carb Vents In The Case O A Holley Must Be Modified To Prevent Fuel Spillage During Bouncing.a Marine Starter And Alt Are A Must.the Difference With Fuel Pumps Is That If The Diaphram Leaks A Line Sends The Fuel To The Intake Instead Of The Bilge.good Luck Hope I Was Of Some Use.i Have Converted Vw Diesels Mercedes Diesels Ford Gas And Chevy Engines With No Problems.these Are Guidelines For Cruisers Not Peformance Hulls.

 

There are advantages to auto engines in boats.