Let me start by saying this is my first post here. I have lurked on this site over the years as I stumbled upon it originally while looking for how to "mod" 9.9 hps to 15's lol. Since then I have found my way back numerous times but never had any questions worthy of the board due to the small outboards I run on jon boats. But finally I had a reason to join and am happy to be here. I hope I can contribute to some degree.

To my issue at hand... I am looking to purchase a 1988 Yamaha 30hp 3 cylinder. The motor has duck hunter influences and was damaged due to the point it needed to be rebuilt. Powerhead and lower were rebuilt and packaged with a new Edge boat to the current seller. Story goes dealer never replaced the lower oil upon the sale and seller basically ran it dry. Obviously he had lower issues and that's when he discovered a bone dry lower. Seller and a friend rebuilt it themselves where they also discovered the lower unit had been cracked and welded. After fixing he said it worked fine until it failed again and now will engage in reverse but not forward. A cracked lower paired with a rebuild does raise my eyebrows but if this was a duck motor I can see it happening. Was told it has 40 carbs fwiw. No clue on tuned exhaust, shaved heads, lighted components, etc though.

I say all of that to say that while I'm confident I could get a good quality lower casing rebuilt, I am not as confident on one that has previously been cracked. So I'm basing my offer on the assumption that a new lower unit or lower unit casing will need to be purchased. So far I have had poor luck locating any for sale that aren't already professionally rebuilt which are well out of my price range.

The real question becomes, will a lower from any other model fit this 1988 30hp aside from other 30hps in the 87- 90 something range? Are there any that are direct bolt on with identical gear ratios? There are a good bit of 40/50hp ones available. I would assume there is not much crossover, however, I do recall seeing posts elsewhere that I can not find now that said the 30hp lower gearbox was a weak link and many upgraded to a 40/50 lower but required slight modifications. But I could be totally off. Any help would be very much appreciated and thank you in advance.