Yamaha 70hp Conversion

Blue Dawg

Well-known member
Joined
Aug 20, 2013
Messages
49
Reaction score
0
Location
New Midway, Maryland
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.
 

JL8Jeff

Well-known member
Joined
Oct 26, 2013
Messages
948
Reaction score
23
Location
Ewing, NJ
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

Member
Joined
May 22, 2022
Messages
12
Reaction score
2
Location
Commerce, GA
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

Well-known member
Joined
Aug 20, 2013
Messages
49
Reaction score
0
Location
New Midway, Maryland
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

Well-known member
Joined
Oct 26, 2013
Messages
948
Reaction score
23
Location
Ewing, NJ
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
 

Attachments

  • cmc_riser.jpg
    cmc_riser.jpg
    21.5 KB · Views: 96
  • lowe_trimmed1.jpg
    lowe_trimmed1.jpg
    442.1 KB · Views: 96

Wirenut

Member
Joined
May 22, 2022
Messages
12
Reaction score
2
Location
Commerce, GA
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

Member
Joined
May 22, 2022
Messages
12
Reaction score
2
Location
Commerce, GA
C3E8D7A2-5093-4E8A-9746-D777BF7AC5FE.jpeg
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

Member
Joined
Jul 27, 2011
Messages
21
Reaction score
4
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

Well-known member
Joined
Jun 7, 2010
Messages
696
Reaction score
33
Location
Rural NY
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.
 

Latest posts

Top