18' SEACRAFT POWER?

TOPCONTENDER · #1 02-23-2004, 11:15 AM

I AM IN THE PROCESS OF REPOWERING A 18' SEACRAFT. IT HAS A 1998 115 MERCURY. I AM CONCIDERING A F115 YAMAHA, F150 YAMAHA OR A VMAX 150 CARB. DOES ANYONE HAVE ONE RIGGED WITH THE ABOVE POWER? THE BOAT HAS A 20" TRANSOM. DO I NEED TO RAISE IT TO A 25" FOR THE ADDED WEIGHT OF THE 150. WHAT KIND OF PERFORMANCE WOULD YOU GET WITH A 150?

ScottM · #2 02-23-2004, 02:17 PM

Topcontender,
One of the members has (or had) an 18 with a 150 HPDI on a raised 25" transom, and another member has an 18 with a 175(?) on a manual jack plate. As is typical with SC's, the back of these boats sit very low, so you may want to stay away from the 4-stroke due to excess weight.

Ryan · #3 02-23-2004, 04:26 PM

topcontender,
as far as weight is concerned,the stern will sit low so a lighter motor would be ideal, however i have seen 18sc's with 175 and 200hp on them so it really depends how fast you want to go. Fyi my 20 with a 150 evinrude will hit 48mph wot on a gps. the motor is an 84 so with the same 150 on your boat you should be somewhere around 55-58 mph, I think. As far as raising your transom, yes raise it up to 25 if for nothing else keeping wates out when you drop in/out at the ramp.---beagle

Mark · #4 02-23-2004, 04:51 PM

use the lightest engine you can. I had an 18' with 140 Evinrude on it as well as a 130 Yamaha later on. Any of the engines you propose will be plenty of power, just pick the one that is the lightest weight. And raise the transom if you can.

don't forget to add trim tabs either, it makes a world of difference on that boat.

TOPCONTENDER · #5 02-23-2004, 05:51 PM

WHAT KIND OF SPEED DID YOU GET WITH THE 140? WHERE YOU STANDING IN WATER?

Mi Time II · #6 02-24-2004, 04:22 PM

Hey TOPCONTENDER, mine is an 18 with a 1992 175 rude she is a little low in the water but not to bad, as long as i dont have everybody in the back of the boat at once. as far as speed , at WOT it use to be about 49 almost 50 but i think in her old age now she gets about 47 WOT on the GPS. Shes also a sucks gas like crazy. Im considering the new 150 Ficth to keep the weight down and still get better fuel millage while keeping the HP up with out droping to a smaller 4stroke. Come to think about i think i posted about this same subject ti another thread. Oh well just my $.02. Oh and mine has the raised Transom.

Mark · #7 02-24-2004, 06:50 PM

In the '77 18' with the 'rude 140 your feet were wet if you took the plugs out of the scuppers and were in the boat anywhere aft of the console. If you were not in the boat, you could leave the plugs out of the scuppers and be ok.
Speed? it was a tired engine but ran about 33kts on the gps. I usually ran it at about 4000rpm and that came out to about 26kts. If you want the 18 for speed rather than fishing, put a floatation bracket on it and mount twin 225's on the tail [img]/images/graemlins/grin.gif[/img]

Flatline · #8 02-24-2004, 10:47 PM

I have an 18 with a 150 rude on it. I have extra weight to push b/c I have external live wells on the transom. 25 gallons each. WOT on GPS is 38-40 knots. Gas is a problem because my average trip is about 60miles and only a 50 gall tank. I would go with the smallest possible to get the speed and economy you want. Im thinking about yamaha too. 150 DFI. Dont know yet.