Yamaha 70hp Conversion

[Blue Dawg]

Considering converting my 2019 70hp Yamaha from prop to a jet. How involved, costly, worth it? Most water I now fish in is rocky. Opinions please.

 

[Wirenut]

How big is the boat it’s hanging on?

 

[JL8Jeff]

I think the jet conversion kits run around $1700-2300 range but with the supply issues the last couple of years, you might want to check with Outboardjets to see if there is a delayed timeframe. The 70 prop will feel like a 50 hp with the jet and you'll use more fuel while going slower. That said, I'm so used to the jet that I tend to run in some really shallow water and don't worry about it which is nice. I've never done the conversion so I can't say how hard it is.

 

[Wirenut]

Conversion isn’t hard at all. Simply remove lower unit and bolt the pump on. The more time consuming part is getting the mounting height correct.

 

[Blue Dawg]

Wire nut
Boats an Alumacraft 18/72 tri with center
Console
Guessing a Jack plate? I’ll measure the Tran some tomorrow. Sorry for slow response. Family illness

 

[JL8Jeff]

You could go with a jack plate or CMC riser plates. The jack plate will set your motor back about 4-8" but allow you to adjust the height easier. When I mounted the jet on my boat, I started with it on the transom and kept going up a hole and trying it out until the spray back was too much and went back down a hole. I ended up almost 2-1/2" above the transom and mine is a short shaft. I also had to add transom wedges to get rid of porpoising.

https://www.amazon.com/dp/B003S8XX5A/ref=as_sl_pc_tf_til?tag=tinb0ab-20&linkCode=w00&linkId=&creativeASIN=B003S8XX5A

 

[Wirenut]

I normally use riser plates. No reason to change the height once you get it right. That being said my current boat has a jack plate with a 4” setback. The tunnel is built to the intake so there’s no issue with splash or drag. Instead of buying the risers from TH Marine I order 3”x1/2” angle aluminum and cut it to the length I need. Fun to tinker with

 

[Wirenut]

This is a 50/35 that had the lower unit swapped out on my son's boat. I cut the angle and had it mounted in about an hour. It’s a long shaft

 

[Vol423]

I have done the conversion. Unfortunately the pump is the same one used for the 60 Yamaha motor. So with the rpm the same you get 60 HP performance from your 70 HP motor. The man Who bought the boat loves it. The 70 is a great prop motor. I would suggest selling that and buying a jet. For conversion You need to buy the pump for about $2500 retail. 9 month back order the last time I bought a pump in 2022. Shift and throttle cables might need to be changed. You need to raise the motor on the transom. I suggest a mini jackplate for about $900. You may need to get extension plates also. About $120.

 

[FuzzyGrub]

The OutBoardJets website has allot of info: Info From hull, power, and set-up, to their installation manuals. There should be enough info for you to determine if it is something you want to tackle or not. If I recall correctly, deliveries are out to March 2023.