Re: restoring 1965 Gulfstream Runabout
Hi Dave,<br />Now you get to hear about the "black anchor" side of the coin....The info from last post about changing engines...Hogwash...On a merc outdrive, there is no physical connection of the engine to the drive unit, other than the driveshaft slip fit into the drive adaptor on the flywheel...no bolts etc. In fact, it is common to remotely mount the engine amidships, and couple engine to the outdrive with a driveshaft very much like your car.(you won't see that on an OMC stringer mount!) I've seen everything from 4-71 Detroits, to 3208 cats, to three cylinder Isuzus with a merc drive behind them...NO adaptor necessary. This is done to move weight forward in the boat for better ride characteristics...but I digress...The only items you would need to mount any GM(chevy) engine or a small block Ford are the correct bell housing, and drive plate/isolator which bolts to the flywheel...readily available literally everywhere The forward motor mounts would have to be for whatever application you decided to install,and the appropriate exhaust configured. The previous poster has the dinosaur...On the OMC stringer-mount drive,the transom bears no load(good), but the whole engine has to move to trim the drive,(bad),and there is a gaping hole in the transom about 16" square(also bad) covered by a big piece of rubber(bellows) to allow the engine and drive to move as a single unit in order to achieve trim. Many of them were shifted by electro- magnets in the lower unit which are sometimes troublesome and require disassembly to parade rest to repair,and a broken wire can leave you dead in the water and stranded. I'm not saying it's a bad drive, I've worked on many and owned one or two, but there is a reason that OMC abandoned that design for one very similar (identical?) to mercruiser. The merc has a driveshaft/2 u-joints that allows the drive to trim independently of the engine. If you have ever seen a manual transmission on a chevy,(or anything else,for that matter) you know how the trans shaft slips into the clutch. That is exactly how the merc drive couples up..The drive is monted to the transom externally.Only the shaft ,exhaust, and raw water penetrate the transom(and hydraulics) Now, here's the rub,,, the lower unit for a six cylinder uses a different gear ratio than that of a V-8...changeable,but expensive.(and requires very close tolerences,special tools,precision measuring devices, factory jigs, etc) Not a job easily done by even a mechanic of some experience,without proper tools and training. Why do you want to change everything? Much easier to rebuild what you have...That is a very economical engine to maintain and super- simple...I would have the drive seviced and pressure tested,replace the gimbal bearing and u-joints,the three bellows, and shift cable if needed.(drive service should include a water pump rebuild)That would be 4 to 6 hundred bucks in parts as opposed to thousands for a new drive,and thousands (really!) more for the new transom assy and gimbal housing.(not interchangeable)Add anotherthousand or so for a new hydraulic pump,cylinders, and lines, and you're almost there...(but not quite..)<br /> Then assess the engine and determine what is needed...but do yourself a huge favor, and no matter what, throw away the old exhaust system and replace it with NEW ONLY..Trust me on this..it is the #1 reason for premature engine DESTRUCTION...PERIOD....Not used...NEW! I can't stress that enough. That means new exhaust manifold and riser... With the price of fuel the six banger will serve you well,it won't be the fastest boat on the lake, but that is not a hot rod hull by any means...hence the name runabout.And stay away from the Chrysler products, they have not been used in new marine apps. in years!<br /> If you get serious about it I will be happy to provide you with places to get parts etc. at lowest possible prices...(I've been in the marine business for 25+ years and I have lots of sources)and help you with tech questions...You can post back to me in this thread or post to my group on google called Bad Boat Biz. Good luck to you.<br />Best Regards,<br />markvictor<br />(a "black anchor" certified tech)
Your going to have to wait for the defenders of the Black Faith to pass comment on updates and interchangability. I can fairly well state this, I doubt you can change motor brands. They all have different bolt patterns and no one makes adaptors for them.<br /><br /> 
