=stern drive question

drives during those years are usually referred to by the horse power designation of the engine in front of it, in your case it would be a 165. Most of those drives are generally referred to as MC-1 drives, the MR(Mercruiser revised) drive was an early version of the Alpha 1, having the upper drive shaft bearing in the lower unit flipped over for better load control. The true Alpha one had a redesigned upper gear case to go with the internal changes of the lower. If you want to up grade an MC1 to an Alpha 1, you will need to keep the input shaft off of your drive
 
i was either gonna upgrade to a newer model or was just trying to get an idea to go through it and replace some parts boats has been sitting four years till i bought it
 
the best deal going is the sterndrive engineering drives(SEI.COM), you can replace just the lower at first, or the upper
 
an alpha (gen 1) will bolt right up... you should have a 1.98:1 ratio... a 1.47/1.5 will also work but will require a prop with less pitch and may cost ya 1 or 2 mph
 
theres a boat shop that is like a used parts wharehouse for parts ill try there the sei took me to a scrapbook site thatnks for the help
 
no prob.... My 76 merc 165 hp 250 ci had a 1.98 It came in an 18' sea sprite tri hull. I put it in a Carver 2667 santacruz flybridge sportfish.... I guess they came with 1.65 also tho?


was an awesome engine.... did over 40 in the sea sprite and 25-29 in the 5500 lb (empty) carver depending on how heavy she was loaded up to 6 people 100 gal fuel and 60 gal water
 
sounds like someone swaped the drives on that boat, 1.98 ratio is for the 2.5/3,0L four cylinders, the 3.7L 4cylinders and the v6's used the 1.84, the 5.0L V8's and the inline 6's used the 1.65, the 5.7's used 1.5 and the 7.4 used 1.32. The gear numbers changed a little when they went to Alpha 1 gen II, but they a were close to the same numbers, high altitude gear sets usually changed to the next gear ratio up from the standard, the 1.5 hd is the best set available for strength. You can use an Alpha 1 gen I lower any any of the earlier drives, the uppers will also interchange(you have to make sure you keep the correct length input shaft to the engine), the big advantage in an Alpha is the lower unit, they flipped the upper bearing and cut the gears different, it makes the lower 7 times stronger than the MC1 type lowers(has the spring loaded pin on the top of the shaft), the uppers did have better cut gears and bigger bearings, but it wasn't as much of an improvement as the lowers. If you try to bolt an Alpha 1 gen II to an early transom, it can cause all kinds of issues, I've sen it done, I don't know exactly how, but you have issues with shift shafts, and trim cylinders. If you have to do much to the transom, its a good idea to swap up to the A1 gen II transom and drives, they're a lot of improvements to make the later drives/transoms. Then you get into the engine bell housing/transom plate issues, but that's another story. There are some early A1 gen II boats out there that can be had for cheap(bad floors, bad transoms, interiors, etc) that make good swap material for fixing up an older boat
 
ive written all that you guys offered in my notes i been taking thanks for the help im posting pics of her all the way apart as soon as i figure it out
 
Ok so upon talking to the friend I got the engine from, he did swap the upper to one from a 4 cyl after hitting a stump at wot... I had known that before but thought he said the ratio stayed the same.... now he tells me that it was higher before (1.65):zip:

anyhow, FWIW I tried both 1.5 and 1.98 with various props on the heavy boat and all around performance was much better with the lower gear about 3 mph on top end at the same rpm and amazing acceleration..... she jumped out of the hole better than many smaller boats with more power
 
the higher ratio(numerically) works better on heavy boats, as long as you can prop it out. A 1,84 may work a bit better, but if what you have is working for you, don't worry about changing it.
 
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