20 foot seacraft power options

[rbandy]

Hello, I'm glad to have access to such a wealth of knowledge. I am creating a 20' classic from a bare hull and liner that I acquired and I'm trying to create a machine that is unique and usefull. I will be finishing the build with custom console and leaning post and all the work will be directed towards weight savings for efficient use. I have raised the floor to try and maintain a self bailling cockpit and I've acquired a 60 gallon tank that I will mount as far forward as possible. I have been pondering all the different power options and see that alot of the people on this forum prefer the 140 Suzuki 4 stroke. I was actually thinking that an older 150 merc would be ideal because of its light weight. I'm trying to do this on a budget and use older technology for power. Something cheap and readily available. I have (2) 3 cylinder OMC 70's, 2000 model, as a matched pair. The weight of this pair is close to the 140 Suzuki 4 stroke. Will I receive benefit or additional lift from two wheels? Has anyone here powered with twins? My concern is that 500lbs is too much weight for the boat to plane at slow speeds. I haven't had or ridden on these boats before.
Any imput would be appreciated.

[Bushwacker]

You're right to keep an eye on engine weight, because balance really affects performance and ride, not to mention self-bailing capability. Most of the new 4 cyl 4 strokes are almost 500 lbs if you look at wet weight and include the cowling, and that's too heavy for the 20' hull IMHO. Heavier engines will increase min planing speed, and the cc models seem to be more stern heavy than the Seafari, so I'd try to mount the console and batteries as far forward as possible. My Seafari would easily plane at 12-13 mph with a 300 lb V-4 and the boat rode very well in rough seas. Current setup will do the same, but it took a stern-lifting 4B prop to get there. The 140 Zuke and 150 (actually 165) E-Tec both weigh about 429 lbs and are about the heaviest I'd consider. Unless you want twins, I'd go with the small V-6 Merc for min weight and decent mpg. Check Big Shrimpin's posts for his results with that rig. He's one of the resident wizards on setting up those motors! Good luck with your custom rig! Denny

[rbandy]

Thanks Denny, That 12 to 13 mph plane is what I'm looking for. I wonder if the guys with the 4 strokes can plane slow like that with tabs? Are there any twin rigs out here?

Reid

[Bigshrimpin]

80's 150, 175, 200 mercs are good picks. So is the 130 yamaha.

I can plane below 12mph with my seafari now and I'm averaging usually better than 3.5mpg at a 30+ mph cruise (even at 35mph). 175/200 2.4L weigh 360lbs and the 135/150 2.0L is closer to 380.

looks like the factory powered the 20 with 2 3 cylinder omc's at one time, but I prefer 1 big motor and a kicker.

[rbandy]

Thanks Bigshrimpin, I appreciate you chiming in. I feel the twin option is more viable now seeing it in some factory literature. That boat looks low in the hole though. I think it would be interesting to power with twins, but it goes against my better judgement. Maybe I can continue with the project and still keep the door open to rig it either way. Your weights indicate that the 175/200 2.4 is lighter than the 2.0 liter. Are there any downsides to the 2.4? I like to keep my motors high in general to minimize appendage drag. Most of the time I'll set my cavitation plate 1.5 inches above the horizontal plane of the keel. If the boat blows out bad under normal conditions I set up so I can lower 1 hole from my high mounted position. In other words I keep the transom clamp about an inch above the glass. With the Seacraft it appears a 20" leg could be used if I trim just alittle glass off the transom well. Is this a bad idea? Are the boats marginal in this area with regard to taking water over the stern? Do they like to ventilate or blow out easily? Sorry for all the questions but if I'm gonna go looking for a merc I quess I gotta figure this out...Thanks again, for posting that brochure and all your help.

Reid

[eggsuckindog]

My '94 200 XRi is hard on the transom and is still about 1.5" above - boy would I like a Mirage +