Boat Engine Questions...

[Alphacowboy]

Ok, so my brothers and I may have scored a new boat, for FREE Its a 1991 20' (I think, might be longer) fiberglass cruiser, in perfect condition. Inboard V6 2. 8ltr GM piece of crap. The interior is perfect, the whole damn thing is in awesome shape! BUT, they had an engine fire, that didnt damage the hull, just the engine. The owner said it overheated and lit up. My question is this, what are some of the options that we could look into as far as fixing, or upgrading this bad boy. Maybe well get lucky and it turns out it was just an electrical fire and some replacing of parts fixes it, but if it truely did over heat and the engine is toast, what can be done? Now, I know its crazy, but can you pull the v6 and drop a v8 in it? I know they are suppose to be marine certified engines, but what does it take to get an engine marine certified? Reason I ask, is that we have a EFI 350 out of a 94 GMC suburban that runs PERFECT! It purs like its new, no leaks, and since its still in the truck, we have all the wiring needed to plop it in there (if it fits) and make it run. I know that the 4. 3ltr Chevy shared the bolt pattern for tansmissons, so I am wondering, did that share the bolt pattern with the 2. 8? Maybe I am just dreaming, but this could be a sweet, and CHEAP way to make this boat water worthy again, and put some major HP in it too!



Thanks in advance for your help.

 

[Joe G.]

IF the engine will fit in the same place and will bolt up to the output you will need marine manifolds.

 

[Alphacowboy]

IF the engine will fit in the same place and will bolt up to the output you will need marine manifolds.

I am sure they put 350s in boats, so where can you get manifolds from?

 

[Joe G.]

Check with a marine hardware store. If you are in an area where there are no marine hardware stores go to a marine dealer. A marine engine is cooled by the water it floats in so you have to have some way to get it into the engine. The method used depends on if you are in fresh or salt water. Some use a heat exchanger regardless of salt or fresh. In some fresh water toy boats the water send back overboard through the exhaust manifolds. So you need to know how the cooling system works on the boat and what kind of modifications are necessary for the engine. You also don't want a red hot exhaust manifold in the boat so it has to be cooled even if you use a heat exchanger. .



You will want to check the existing cooling system to see if it is plugged up to cause the over heating condition.



Best to get advice from someone who knows what he is doing and can look at the boat and your engine.

 

[Alphacowboy]

thanks guys, hopefully the boat will be in our hands next week so we can get a better idea what we are looking at.



I know they use the water (fresh in our case) to cool the engine... so we'll have to see how this boat is setup.



Not to often you are pretty much offered to take a boat for free. So even if we put 1k in to it to get it to run, it would be worth it. The wife wants it gone asap, so if she can convice the husband to dump it, its ours. they want a new boat anyway, and dont wana spend the time or money fixing this one.

 

[TORQUE THIS]

NEVER... NEVER... NEVER use an automotive engine!!!!!!!!!!!!!!!!!



You need a marine alternator, and a marine starter first of all, with out these you stand the change of having an explosion. Buy the time you spend all the money to convert an auto power plant to marine standards, might as well buy a drop in marine crate motor and be done with it.



If it had a Mercruiser, they will have a exact fit replacement. Most times you can score a motor and outdrive combo for around 7K...

 

[Joe G.]

AH, forgot about gasoline. All the boats I'm had anything to do with for the last 30 years have been diesel. Can't have any arcing and sparking in a gas fueled boat. Good way to try to make obit.

 

[Sageair]

I'm not sure if you really meant it is an inboard or a stern drive. If it's a stern drive there is most definitely a limit as to how much horsepower it can handle over stock.

 

[Dl5treez]

Alphacowboy,



Not knowing the exact make & model of boat I can only guess, so bear with me:



The 2. 8 GM V6 is a 60 degree V, whereas the 4. 3 V6 and all the SB V8's are 90 degree V. So, unless the gearbox uses a removable/replaceable adapter plate you're out of luck on a swap to a bigger engine.



If you can swap in something larger, keep in mind the position of the molded box/stringers for the engine mounts. You may find hull work necessary to fit the larger engine. If the m'fer optioned a V8 it might be a bolt-in, but boats are full of rather unpleasant surprises and things like fuel plumbing, the cooling system, exhaust etc, can become a nightmare quickly... . and like was already said, your outdrive might not be large enough to handle a more powerful engine. $7,000 is definitely not a stretched estimate to perform a drop in conversion.



Other than the exhaust manifolds, the only parts which need to be marine grade are the starter, alternator, distributor & plug wires, carburetor (if equipped with fuel injection all the FI parts will be marine approved), fuel pump, and air filter/air cleaner assembly. You actually don't *need* to use anything "marine grade" on the engine but with the great chance of severe explosions it's highly recommended. If you live in an area where the Coast Guard or state inspects boats yearly or bi-yearly for "code" then you'll definitely need all the above mentioned hardware, and probably a few more I've forgotten.



You can use automotive engines as a base to build off of, but keep in mind the "marine grade" long blocks have brass casting plugs and usually have different cams, heavier duty valves, and, from a durability standpoint, sometimes stronger internals as a whole.



So now if you're thinking "Crap I'm screwed" and don't want to mess with the boat, be happy that the kind folks at GM have completely figured out the 2. 8 is an anemic, steaming pile of crap and have gone to great lengths to do something about it.



Look into a 3. 1 or 3. 4 GM V6--basically identical externally to the 2. 8, everything bolts up, and all the 2. 8 problem areas have been addressed in larger, more powerful (much more) packages. Not to mention all the machine shops & engine building shops around the country who figured out how to get 600+ *reliable* racing horsepower from a 2. 8. Also, GM stopped using the 2. 8 in 1989, and had switched to the 3. 1, but in the marine world engines are used longer, usually. A '91 marine 2. 8 will be loaded will all the upgraded internal parts and has the much better lower end similar to the 3. 1/3. 4 engines.



That little engine can be made to scream, if you want it to.



Dan-

 

[KBennett]

Dan is right. My wife has the 3. 4 in her Pontiac Transport and it moves pretty good, a lot better than the old 2. 8 motor. She gets about 20-22 MPG on the highway at 75 MPH.



A 350 is a lot of power but it also uses more fuel, something to think about with gas prices these days.