18sf repower questions

dragin22s · #1 07-17-2008, 01:00 AM

i have a 1977 18sf that i stole for $800 couple months ago w/ trailer and motor and is soild in and out but has a dingy 70hp evinrude on it now, now i haved picked( which was another steal) up a 200hp yamaha vmax 3.1 2000 with all the controls and hydr steering. my questions is it to much motor for the boat? i have seen other 18sf with 175-200 on them. also what issues might i have if i do put it on?

Snookerd · #2 07-19-2008, 03:44 PM

The 18SF's deck will not drain above 400 lbs. of motor weight unless you raise the deck. Many people will go up to 425 lbs +/- and just use ball scuppers and interior drain plugs. IMHO, all of those 200hp 18SF's are lighter 2strokes around 425lbs. That 3.1L 200 Yamaha VMAX you mentioned is 509 lbs. and would not be a good match. We had a 1996 150 Johnson that went almost 50 and was well matched besides the marginal water sheading of the slightly higher v-6 weight. The 130 Yamaha on my 18SF was the best weight to power ratio IMHO

dragin22s · #3 07-20-2008, 12:09 AM

thanks when i was looking all the newer (00-up ) yamahas from 150 to 200 wieght about the same and i thought the 3.1 wieght 466
what about 150 saltwater series ?
how long have u lived in bradenton i lived there from 1994-2004

Snookerd · #4 07-20-2008, 02:00 PM

The SWS oX66 150 weighs around 450 based on the 2.6L block with the FI gear. The Yamaha carbed 150 is 426. I have been in Bradenton since 1998. Jupiter is where I spent the 1st 22 yrs. Where are you located?

eggsuckindog · #5 07-20-2008, 05:07 PM

what he said, mine had a inline 6 115 merc and was just fine really, weight will kill

2182 · #6 07-20-2008, 07:30 PM

ive got a 200hp merc on my 18, she runs great, drains proper, etc. definitely likes to slurp some gas though but oh well. not sure on weight since it came w/ the boat. sounds like you got a great deal on both boat/motor; i would say roll with it. on the flip side, ive had my seacraft a month or two. a lot of the guys on this site know them inside and out. just alittle support from someone w/ an overpowed boat!!

small45 · #7 07-20-2008, 09:36 PM

i've got an '89 omc 120 on mine. it pushes 32mph gps with two people and full of gas. not bad but it is VERY marginal on the self bailing. i don't know what the weight of the 120 is, but i have a new yamaha 150 carb motor that will likely go on it this winter

dragin22s · #8 07-20-2008, 09:38 PM

snookerd- psl now (port st lucie )i had family in the farms and my girl lived in the farms to.

224466- what year is your motor/model # i also saw i 18sf on the first page for this site with a 150 vmax which i think wieghs 50 pounds lighter then 200 vmax my ownly concern is to much water coming in over the transom in to the splash well but i think im going to put it on and see i what happens

Snookerd · #9 07-21-2008, 02:00 AM

Quote:

drains proper, etc.

224466-Your 200 Merc must be pretty light to properly drain vs. a 509 Lb. 3.1L 200 Yamaha V-MAX. As I said before, your type of set-up with power and weight is not outrageously heavy, just overpowered. I have had 3 different motor set-ups on 2 different 18SF's.Your 86 18SF should be a 25 inch transom and draggin22s Potter era 18SF would be a 20 inch transom, especially to allow for the VMAX. So, your comment to go for it is bad advice and could put people in a dangerous situation. The transom cut out is too low and will quickly allow water to get in the splashwell. Do a search on the 18SF power on CSC and see the info that comes up since 2/2002.

eggsuckindog · #10 07-21-2008, 02:27 AM

My 20 MA won't drain at 406 with a 20" transom, although the transom has nothing to do with scuppers draining