Replacing 305 Chevy, Have some ?

[par1969]

I just pruchased a 1978 Sea Ray with a new merc. alpha drive and a blown(rod) 305 chevy. I going to replace the 305 with a 350 and would like to know whats required to go from the 2 piece rear seal engine to the newer 1 piece rear seal engine? Also since the 305 was a two barrel and I'm changing it to a four barrel, can I buy the linkage components somewhere? I've rebuild many auto V-8's but what should I look for when buying or building a marine engine? I already know about brass freeze plugs but anything else I should know? how much HP can the alpha 1 take and still be reliable? Thanks is advance to any one who can help answer some or all of these questions.

 

[Fishermark]

Re: Replacing 305 Chevy, Have some ?

I needed to do the same when I purchased my boat - it too came with a 305 and I put in a 350. After evaluating things, I decided to go with a complete new crate engine with all new components. That way you start out with new exhaust manifolds, risers, starter, etc. If you know for sure all that other stuff is okay, then if you want to just replace the long block, then go at it. All the internal stuff is the same - you already mentioned the freeze plugs - you ought to get a marine grind cam - or a truck cam is similar as I understand it. So far as the one piece - versus two piece rear main - can't help you there. someone will chime in soon.

 

[DHPMARINE]

Re: Replacing 305 Chevy, Have some ?

I think the one piece/two piece seal problem really has to do with the crankshaft.It is either internally balanced or externally balanced.<br />This also determines if your flywheel fits.<br /><br />DHP

 

[BinLurkin]

Re: Replacing 305 Chevy, Have some ?

Why does everyone replace the 305's with the 350? I have one of each & can't tell the difference in performance & the 305 is in the bigger boat. It seems like a good engine to me.

 

[Buttanic]

Re: Replacing 305 Chevy, Have some ?

The flywheel bolt circle on the one piece seal crank is smaller than on the twp peice seal and the old splined coupler will not bolt up to the one piece shaft. You will need a later one piece flywheel and coupler.<br /><br />Buttanic

 

[Fishermark]

Re: Replacing 305 Chevy, Have some ?

Why does everyone replace the 305's with the 350?

BinLurkin does bring up a good point. The thing to keep in mind is the rated horsepower of the engines. You can obviously obtain more horsepower with a 350 than with a 305, but if I had it to do over again I would have gone another route.<br /><br />For example, I mentioned that I purchased and installed a Mercruiser crate engine - it was a complete package - just hook up the water and electric and you're done. This was a carburated 2003 engine. I found out (after the fact ) that I could have bought a fuel injected 305 from Mercruiser for the same amount of money - with basically the same rated horsepower.<br /><br />Just be sure to do your homework before buying anything would be my suggestion.

 

[Buttanic]

Re: Replacing 305 Chevy, Have some ?

There is an old saying amoung racers and hot rodders that "there is no substitute for cubic inches". Small engines can produce equal or more power than a larger one but the smaller engine will have less torque and have to be run at higer RPM to compensate for the smaller displacement. If power is the main issue I would rather have the carburated 350 rather than the enjected 305. <br /><br />Buttanic

 

[Scaaty]

Re: Replacing 305 Chevy, Have some ?

I'm with Buttanic.......Jap bikes with tiny motors produce more power than a big old Harley, but 20 years later , which is still running?

 

[cmyers_uk]

Re: Replacing 305 Chevy, Have some ?

That said new technology can provide huge benefits not only both power and torque but economy apply that with cubic inches and you get a really good engine. Look at things like variable valve timing to see how technology can provide improvements across the rev range.

 

[Buttanic]

Re: Replacing 305 Chevy, Have some ?

Granted technology provides benefits but it comes with more complexity. I would prefer something that is simple and easy to diagnose and fix if I find myself bobbing around 30 miles offshore with a problem.<br /><br />Buttanic

 

[trog100]

Re: Replacing 305 Chevy, Have some ?

technology dosnt have to mean more complexity and less reliability.. technology can be used in many ways.. it could be used to make things cheaper but still reasonably reliable for instance.. or it could be used to make things a litle more expensive but last forever so as they never went wrong in the first place. <br /><br />the reasons we have pretty much the same boat engines as we did forty years ago is a simple one.. lack of competition in the "boat" world or at least lack of competition compared to say the "car" world..<br /><br />with cars they have to produce newer and more complex cos thats what we demand.. we demand this cos all those car makers desperately trying to sell their cars in an overly competetive market tell us we are better people if we have this complexity and a new car every year thats more "advanced".. and that somehow our lives will be "better" because of all this....<br /><br />with boats they dont have to do this and with boat engines its even worse.. there really is only one "real" engine maker and thats GM.. to GM the boat engine world is a really pissy little world and they would have a good case if they stopped making the things at all.. not exactly a scenario to demand "better" more complex and a new model every year..<br /><br />but strangely enough in the boat world.. we seem quite happy with the same stuff as we got forty years ago.. in fact we seem to be busy trying to convince ourselves that its even a good thing.. he he he<br /><br />u have to laff<br /><br />trog100

 

[imported_Pioneer]

Re: Replacing 305 Chevy, Have some ?

I've done the swap in a truck and everything bolts right up except for the flywheel and coupler (as buttanic said). <br /><br />The alpha drive is rated for 300hp.<br /><br />If you a buying a marine engine, I would look for a company with a good reputation and a good warranty that they will backup. Take a look at dougrussell dot com and Jaspar - I've heard good things about both.<br /><br />If you order a tall block, you'll need to locate a sheet metal package for the engine (different valve covers and oil pan). Ebay is a good source for these types of used parts for cheap.

 

[Buttanic]

Re: Replacing 305 Chevy, Have some ?

Until the government cracks down on emissions and fuel consumption in the boating industry the marine engine world will not change. Government regulation, not the consumer is what drove the automobile to where it is now. If it weren't for emission regulations and CAFE standards we would still have carburators and point ignitions. Computer controlled machining has increased the precision and reduced the cost in making parts which generally has helped the power and quality of engines.<br /><br />Buttanic

 

[par1969]

Re: Replacing 305 Chevy, Have some ?

Thank you everyone for your responses. The reason I'm going with a 350 is that the 305 has a giant hole in the block. As long as the engine is not rebuildable I've decided to go with more CCs. All thing being equal a 350 will produce more torque and the cost of both is about the same. Does any one have any recommendations for a complete crate motor from a company they are happy with? Thanks Again.

 

[Fishermark]

Re: Replacing 305 Chevy, Have some ?

I don't remember where I bought my Mercruiser engine from - I got a good deal on it. Here is an outfit that has good prices - there is a Vortech engine on their home page that is $3299. Here's a picture:<br />

<br /><br /><br />Here's the page: ebasicpower <br /><br />This would work well if your manifolds, etc are good.

 

[cc lancer]

Re: Replacing 305 Chevy, Have some ?

to GM the boat engine world is a really pissy little world and they would have a good case if they stopped making the things at all.. <br />-------------------------------------------------<br />Oh to the contrary, my English friend, several years back GM-Chevy division notified all the marine engine manufacturer they were dropping the 305, and it would no longer be available.<br /><br />Mercury marine notified GM if they dropped the 305 they would give more of their business to Ford.<br />Next season you could not buy a 305 in a Chevy car or truck, but Merc. and the other Manufacturers had 305's for sale. This market was important enough for GM to continue to make the engine. This was published in one of the boating mags. and I heard the same thing from a friend who works for Chevy.

 

[Bondo]

Re: Replacing 305 Chevy, Have some ?

This market was important enough for GM to continue to make the engine.

Ayuh.........<br />GM has been building the 3.0l for Well Over 30 Years,+ None of them have gone into Cars Or Trucks..............<br />Just Marine/Industrial...........

 

[JasonB]

Re: Replacing 305 Chevy, Have some ?

I just wish Ford would get involved in mainstream marine again. The competition would be a good thing and Ford makes sopme good engines.

 

[BinLurkin]

Re: Replacing 305 Chevy, Have some ?

Well, thanks for all the good info. I guess I should have known that it all comes down to cubes. My dead arse can't tell the difference. I have put headers on lots of motors & wondered why I did it? I just did a Dodge 360, 1978, & put a rv cam in it & MSD, ignition, & headers. I don't see no improvement. I now understand why you would go to 350 from 305, even though my dead arse can't tell the difference. For what it's worth, BL.

 

[Richard Petersen]

Re: Replacing 305 Chevy, Have some ?

For all us lovers of Japanese car engines. I just spoke with the president of a company in Florida who is building a plant in Japan to build the water cooled exhaust manifolds for Lexus V8 engines. First the lawn mower, then outboard motor, then car, could it be marine engines? Not much profit in selling new Mercs is there ?