Trojan Boat Forum

Would it be possible to replace my failing 318s with GM 350s? Does it matter if they're short or long blocks?

Thanks

Randy

Not knowing whether you have V drives or straight drive would have an impact on swapping chrysler 318's for gmc 350"s. The term short block usually refers to an engine that is Minus the cylinder heads at the least. If your swap is feasable you would probably need a fully dressed and optioned 350 to replace your 318. This would include complete fuel system from the fuel pump to the intake system. New manifolds and risers. and possibly the complete charging and starting system that is on the 350 engine. You still have to consider the transmission and bell housing assembly. It may be possible to use your OEM raw water pump if it will mate up to your new engine. The amount of money you are willing to put out to have a very competent marine mechanic will have an enormous effect on the results you will get. I am not a certified marine mechanic but I am a retired mobile equipment with over forty years of experience and in my time I had to replace one brand and type of engine in equipment with another brand and for the most part it was costly and entailed quite a lot of modifications to the machine . I believe the 318 is a very good engine for its size and if yours were fresh water cooled there should be enough wall thickness to handle a rebore if needed. I think your mechanic will advise you to stay with the Chrysler and a rebuild if needed. My 2cents worth, wish you luck with whichever way you go. Research, Research. Ted

The short answer is yes, And I agree with a lot of what " delusional" posted above. To swap from 318s to GM 350s you really need complete marine engines with bell housings that fit your transmissions. No parts on your 318 will fit the 350, so forget long blocks. You will need both right and left-hand rotation engines or new transmissions.

This is on your Searader correct? What brand transmissions do you have? BW Velet drives or Paragons?


As delusional said a short block is without heads, a long block has heads. To use a long block you need to buy every single bolt-on part and all must be marine. manifolds pumps mounts brackets ignition starters alternators fuel systems cooling systems the list goes on and on. Much cheaper to get complete marine engines and a lot easier.
b
While the swap is not that hard if you have the skills and knowledge, its still a lot of work . By far fixing what you have is easier.

Thanks for sharing your experience and knowledge. I feel as though I am caught between many rocks and hard places with this repower
The technicians at the marina would prefer just swapping out complete engines and not rebuilding the engines. I believe they have little experience with these old engines. So, I found a remanufactured complete reverse rotation engine but could only find a long block std rotation
As the complete 350 are available and less expensive than the 318s is why I was wondering about switching them out I thought two complete engines and rebuilt BW velvet drives would be more easily achieved and offer a greater chance for success.
Now with your input, I am not sure what to do.
Thanks so much. I will keep you posted.