User Tag List
Thanks: 0
Likes: 0
Results 1 to 8 of 8
Thread: building 40 yamaha powerhead???
-
04-29-2012, 09:06 PM #1
New Member
- Join Date
- Apr 2012
- Location
- orangeburg, SC
- Posts
- 2
- Thanks (Given)
- 0
- Thanks (Received)
- 0
- Likes (Given)
- 0
- Likes (Received)
- 0
- Mentioned
- 0 Post(s)
- Tagged
- 0 Thread(s)
building 40 yamaha powerhead???
i have an 1989 yamaha 40 powerhead that i wanting to beef up!! any help guys? where do i start?? would like to turn it into a 70
-
07-10-2012, 11:05 PM #2
5000 RPM
- Join Date
- Feb 2012
- Location
- Canada
- Posts
- 346
- Thanks (Given)
- 0
- Thanks (Received)
- 1
- Likes (Given)
- 0
- Likes (Received)
- 6
- Mentioned
- 0 Post(s)
- Tagged
- 0 Thread(s)
You need to find a tuner from a 50hp,carbs from a 70,(you could use 90hp carbs if ported) shave the head (stock comp is only 130 or so) and if you really want to spin it--weld the crank pins. There is also a wire to the cdi that needs to be snipped or it will limit the rpm (its governed) I can't remember the colour but will find out if you would like me too.
Originally Posted by Dillonwalling09
I would also disconect the oil inj (runs too lean anyways) and always remember to jet it
Fantastic little engines (just like its big brother the 70hp OMC)
Good Luck
-
10-08-2014, 10:39 AM #3
5000 RPM
- Join Date
- Jun 2009
- Location
- Britsh Columbia
- Posts
- 380
- Thanks (Given)
- 0
- Thanks (Received)
- 5
- Likes (Given)
- 1
- Likes (Received)
- 14
- Mentioned
- 0 Post(s)
- Tagged
- 0 Thread(s)
Dont forget a set of Chris Carson or Boysen Reeds, and you can also shave weight off the flywheel.
ON VACATION
-
10-08-2014, 12:32 PM #4
8000 RPM
- Join Date
- Apr 2012
- Location
- windham nh
- Posts
- 3,182
- Thanks (Given)
- 151
- Thanks (Received)
- 117
- Likes (Given)
- 951
- Likes (Received)
- 755
- Mentioned
- 0 Post(s)
- Tagged
- 0 Thread(s)
Is there a rule as to the max percentage of weight that can be shaved from the flywheel and still idle ok? Does it depend on the amount of moving mass (cylinders,etc)?Thanks Gary Originally Posted by BC Black Max
"12" Super Lite Tunnel (11') "88" 25 Yammy twin carb "BANANA SPLIT"
"77" Hydrostream Viper "87" 140 Rude heavy modded w/15" mid, Bobs nose and lwp "DANGER ZONE"
"72" Checkmate MX-13 "80" 75 Rude w/15"mid and Nitro Lu (to be restored)
"Too much is never enough" Keith Richards " Dreams become reality via hard work and perseverance" G.A.Carbonneau
"This coming from an old man that strapped two bananas together, hung a motor on it and calls it a boat" XstreamVking
-
10-09-2014, 02:06 PM #5
5000 RPM
- Join Date
- Jun 2009
- Location
- Britsh Columbia
- Posts
- 380
- Thanks (Given)
- 0
- Thanks (Received)
- 5
- Likes (Given)
- 1
- Likes (Received)
- 14
- Mentioned
- 0 Post(s)
- Tagged
- 0 Thread(s)
We took about 4 lbs off the Tohatsu we did. Its really up to the machinist.
Originally Posted by olboatman
ON VACATION
-
10-09-2014, 05:47 PM #6
8000 RPM
- Join Date
- Apr 2012
- Location
- windham nh
- Posts
- 3,182
- Thanks (Given)
- 151
- Thanks (Received)
- 117
- Likes (Given)
- 951
- Likes (Received)
- 755
- Mentioned
- 0 Post(s)
- Tagged
- 0 Thread(s)
Thanks for gettin back to me! Gary Originally Posted by BC Black Max
"77" Hydrostream Viper "87" 140 Rude heavy modded w/15" mid, Bobs nose and lwp "DANGER ZONE"
"72" Checkmate MX-13 "80" 75 Rude w/15"mid and Nitro Lu (to be restored)
"Too much is never enough" Keith Richards " Dreams become reality via hard work and perseverance" G.A.Carbonneau
"This coming from an old man that strapped two bananas together, hung a motor on it and calls it a boat" XstreamVking
-
10-09-2014, 10:03 PM #7
5000 RPM
- Join Date
- Jun 2009
- Location
- Britsh Columbia
- Posts
- 380
- Thanks (Given)
- 0
- Thanks (Received)
- 5
- Likes (Given)
- 1
- Likes (Received)
- 14
- Mentioned
- 0 Post(s)
- Tagged
- 0 Thread(s)
Machining your Flywheel
Gary,
One more thing I should tell you. The flywheel needs to be balanced after is machined. Only a high performance engine shop around here had the equipment to do it. The ring gear alone is about 1lbs. If you are pull start only, bounce that right away.
It makes the single biggest difference in acceleration.
Originally Posted by olboatman
ON VACATION
-
10-12-2014, 05:24 PM #8
8000 RPM
- Join Date
- Apr 2012
- Location
- windham nh
- Posts
- 3,182
- Thanks (Given)
- 151
- Thanks (Received)
- 117
- Likes (Given)
- 951
- Likes (Received)
- 755
- Mentioned
- 0 Post(s)
- Tagged
- 0 Thread(s)
BC That is the first thing I do to my small twins(pull the ring gear). I would rebalance the flywheel if I had it cut. Was really interested about how far I could have them cut. These are wheels on 25 and 35 hp OMCs -late 70s vintage. Gary
"77" Hydrostream Viper "87" 140 Rude heavy modded w/15" mid, Bobs nose and lwp "DANGER ZONE"
"72" Checkmate MX-13 "80" 75 Rude w/15"mid and Nitro Lu (to be restored)
"Too much is never enough" Keith Richards " Dreams become reality via hard work and perseverance" G.A.Carbonneau
"This coming from an old man that strapped two bananas together, hung a motor on it and calls it a boat" XstreamVking
Reply With Quote
