Re: 1989 88 SPL Conversion to 115???
I am in the middle of changing my 90 hp to a 115...while it is a looper not a crossflow, what i ahve found , PROBABLY applies to your motors as well.
first off just because you look up a part number and it says it fits both the 90 hp and the 115 hp...does NOT mean they are the same.. the heads interchange from a 115 and a 90./..BUT they are different..the depth of the combustion chamber is about .090" deeper on the 90 hp!!!
second, like someone said the BORES on the 90 and 115 carbs are way different...thus the volume of air going through is different...youd need the 115 carbs .
thirdly, while almost every rebuilder will tell you they sell a 90-115 hp block...they cant!! the ports in the sleeves are very different!
the 115 hp ports are larger and closer to the edge than the 90 hp ports. I took a foredom tool and ground the ports on my 90 hp to match those of my 115 hp( luckily i have a 115 already to measure from) as best i can tell all other parts are the same..
I would guess that it is at least as difficult to convert your 88 to a 115 as it was for me to convert my 90 to a 115...maybe even more...since i havent seen the exhaust housing on your motor...
on this picture the port on the right is the original shape for a 60 degree looper 90 hps, the port on the right is about the shape for the same style 115 hp!!
good luck
bob