Classic SeaCraft Community  

Go Back   Classic SeaCraft Community > General Discussion > General

Reply
 
Thread Tools Search this Thread Display Modes
  #21  
Old 04-23-2019, 12:24 PM
Bandit91 Bandit91 is offline
Member
 
Join Date: Jun 2018
Location: South Carolina
Posts: 34
Default

Quote:
Originally Posted by uncleboo View Post
Yes, yes and yes. Check out my thread 'deck replacement'.
Just read through your thread, very informative. That’s a shame about your motor. But you did an amazing job on your boat. It looks great. Going to be a really nice setup with your new power.. Looks like your motor was a 25” shaft on a jack plate, is that correct? Or was it a 20” on the jack plate?

Last edited by Bandit91; 04-23-2019 at 12:52 PM.
Reply With Quote
  #22  
Old 04-23-2019, 12:31 PM
otterhound otterhound is offline
Senior Member
 
Join Date: Oct 2011
Location: Shelter Island, NY
Posts: 235
Default

I have an 18 SF with a 20" transom and '09 Mercury 90 hp 2 stroke. Weight wise at 303 lbs it seems perfect for our 18. It will cruise all day at 25 -28 mph, plane down to 14 -16 with out tabs and top out at 36 -37 with one aboard. It has a 4 blade aluminum Apollo prop, a Doel Fin and the ventilation plate is 1 1/2" above the bottom of the boat. It previously had a '92 Evinrude 120 hp. When we got the weight out of the back of the boat and the motor height set correctly the boat absolutely came alive. Although it's not a rocket ship it's nicely balanced, great in a head sea and economical to run. Best of luck!
Rod
__________________
The older I get the faster I was!
Reply With Quote
  #23  
Old 04-23-2019, 12:33 PM
DonV's Avatar
DonV DonV is offline
Cheap Bastard
 
Join Date: Jul 2004
Location: Apollo Beach, FL
Posts: 3,179
Default

"BTW, the F70 and F90 are exactly the same in terms of weight, dimensions, etc. Only difference, I believe, are the stickers and ECU...and the price"

Not true, the 70 is 1000cc and the 90 is 1800cc, the 90 is much heavier, 100# more. The 70 is only available in a 20" shaft and the 90 comes in 20 or 25". The 70 is basically a motorcycle engine with great HP/weight ratio. It was designed for the 16 to 18' technical skiff market.

https://yamahaoutboards.com/en-us/ho...15-50-hp/70-50

https://yamahaoutboards.com/en-us/ho...115-50-hp/f115

Last edited by DonV; 04-23-2019 at 12:40 PM.
Reply With Quote
  #24  
Old 04-23-2019, 12:37 PM
DonV's Avatar
DonV DonV is offline
Cheap Bastard
 
Join Date: Jul 2004
Location: Apollo Beach, FL
Posts: 3,179
Default

Real quick, back on post #7, the Optimax I mentioned is a 1.5L 3 cylinder for both the 115 and 90, they weigh the same. If they are still available the 115 Opti would work nice on a 18' SeaCraft.
Reply With Quote
  #25  
Old 04-23-2019, 01:38 PM
bmajvi bmajvi is offline
Member
 
Join Date: Aug 2009
Location: St. Croix USVI
Posts: 61
Default

My '75 18 footer had the 20'" transom. Back in '02 the Suzuki four strokes hadn't built up a reputation yet, and I found a 20" DF 140 that the dealer wanted to move. This was in the West Palm Beach area, where there's a good deal of flat water on the Intracoastal and sometimes outside, so you have an opportunity to run fast - but also occasionally pretty rough inlet running and ocean seas. My boat didn't have trim tabs, and don't remember checking low speed plane, but I don't recall feeling that it was an issue. I did however scare the living heck out of myself the first time I tried backing down on a fish out in the open ocean with a little sea running (the boat didn't come with washboards). In short order I made up some hinged boards out of Starboard, which allowed the motor to tilt when folded, and they helped a lot in keeping water out of the boat. I knew the motor put a bunch of weight aft, so I moved the batteries under the console and tried not to load heavy gear in the stern. As Don said a few clicks back, it's a good idea to first try to figure out how you're probably going to be using the boat, and go from there.
__________________
1976 23' Sceptre
1975 18' SF (Sold)
Reply With Quote
  #26  
Old 04-23-2019, 02:18 PM
mikeyk mikeyk is offline
Junior Member
 
Join Date: Oct 2018
Posts: 16
Default

Quote:
Originally Posted by DonV View Post
"BTW, the F70 and F90 are exactly the same in terms of weight, dimensions, etc. Only difference, I believe, are the stickers and ECU...and the price"

Not true, the 70 is 1000cc and the 90 is 1800cc, the 90 is much heavier, 100# more. The 70 is only available in a 20" shaft and the 90 comes in 20 or 25". The 70 is basically a motorcycle engine with great HP/weight ratio. It was designed for the 16 to 18' technical skiff market.

https://yamahaoutboards.com/en-us/ho...15-50-hp/70-50

https://yamahaoutboards.com/en-us/ho...115-50-hp/f115
I stand humbly corrected. I was using the F75 as a comparison. It appears that the F70 and it's weight difference between the F75 is better suited for lighter boats where 70 hp is the upper end spec for mfgrs. power and engine weight, i.e., skiffs. Pushing a heavier boat with a 70 at the 5800 Rpm powerband range would probably require smaller diameter and/or lower pitch prop to utilize full horsepower. I noticed that Yamaha does not divulge torque specs. but using the formula
Torque = Hp x 5252 / Rpm (5252 is a constant)
the F70 yields 63.4 ft/lbs. @ 5800 rpm, the F75 71.6 ftllbs. @ 5500 rpm
__________________
18' SF Seacraft
24' Radon molded hull
24'Radon glass-ply hull
18' Panga
25' Radon (sold 1985)
24' Carolina (RIP) #akaglassfoamtaco
Reply With Quote
  #27  
Old 04-23-2019, 02:42 PM
kmoose's Avatar
kmoose kmoose is offline
Senior Member
 
Join Date: Jul 2006
Location: Ocala, Florida
Posts: 1,571
Default

I think Terry has a 90 Etec on his 18 and it does fine.
__________________
1974 23 Tsunami w/ 300 Suzuki

Last edited by kmoose; 04-23-2019 at 02:47 PM.
Reply With Quote
  #28  
Old 04-23-2019, 03:34 PM
uncleboo uncleboo is offline
Senior Member
 
Join Date: Sep 2009
Location: Edenton, NC
Posts: 1,238
Default

Quote:
Originally Posted by Bandit91 View Post
Just read through your thread, very informative. That’s a shame about your motor. But you did an amazing job on your boat. It looks great. Going to be a really nice setup with your new power.. Looks like your motor was a 25” shaft on a jack plate, is that correct? Or was it a 20” on the jack plate?
20" transom, 20" shaft and I raised the transom 3". 2-1/4" would have been better due to hydraulic steering head, but, I have it worked out. I went with the 3" jack plate solely for the purpose of adjusting the height of the motor without removing bolts.
__________________
1975 SF18/ 2019 DF140
Reply With Quote
  #29  
Old 04-24-2019, 09:43 AM
Beaver Beaver is offline
Senior Member
 
Join Date: Nov 2011
Location: San Diego
Posts: 203
Default

Some more info for the 90...

Bocaseacraft sent me a PM that said his 90 Suzuki goes 34 to 36 mph and has been averaging 6 mpg. In my book those are great numbers for an 18.
Reply With Quote
  #30  
Old 04-24-2019, 09:54 AM
Bandit91 Bandit91 is offline
Member
 
Join Date: Jun 2018
Location: South Carolina
Posts: 34
Default

Quote:
Originally Posted by Beaver View Post
Some more info for the 90...

Bocaseacraft sent me a PM that said his 90 Suzuki goes 34 to 36 mph and has been averaging 6 mpg. In my book those are great numbers for an 18.
That’s good to know, I might send him a pm and talk to him about his setup. Thanks for the info.
Reply With Quote
Reply

Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump


All times are GMT -4. The time now is 12:45 PM.


Powered by vBulletin® Version 3.8.11
Copyright ©2000 - 2019, vBulletin Solutions Inc.
All original content © 2003-2018 ClassicSeacraft