# jet unit swap



## blazer02 (Aug 29, 2014)

Back in the earlier johnson 25 motors many had the small jet unit on them I believe they had like a 5 3/4 auger in them.I don't no how many years had them but i know they 83 and 84s had them.I have been told by a guy that races boats that these generally run better than a 5 7/8s unit like my 2002 model motor has.the reaaon being even though they move a lower volume of water that because of this the mantain a higher rpm and get to it faster and the 5 7/8s are trying to move to much and have a hard time making the peak rpm so the thrust isn't as hard.anyone else heard of this or have any thoughts on it.can one of these units bolt up or be modified to fit my 2002 25 horse.i have been told no by one shop wanted to sell me a motor not sure by another yes by a guy that does a lot of jet work on them.thoughts on this


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## Lil' Blue Rude (Aug 29, 2014)

Does your motor have the little aluminum adapter plate in between the jet and the mid section. If so I figure that the small unit would bolt up to your mid like the old ones did. Not for sure though.


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## blazer02 (Aug 29, 2014)

[url=https://www.tinboats.net/forum/viewtopic.php?p=364865&sid=15dd8972cb2b7b24d325117cb51650d4&sid=39c75148dbe886cfc85e17479c27e571#p364865 said:


> Lil' Blue Rude » 29 Aug 2014, 20:24[/url]"]Does your motor have the little aluminum adapter plate in between the jet and the mid section. If so I figure that the small unit would bolt up to your mid like the old ones did. Not for sure though.


Mine has a black spacer above the jet around one inch thick i believe it aluminium and its what your talking about.has a bolt that runs through it into jet on the back below exchaust.


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## Lil' Blue Rude (Aug 29, 2014)

yeah that's the plate. I'm not sure I know they made 2 different lower units for these motors. They use to use a over the prop lower unit then they started making a through the hub lower unit. That just means the earlier motors exhaust came out just about the prop and the later actually came though the middle of the prop hub. So honestly don't know if it will be a bolt up and go or if it would take some modding.


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