Repowering 18' Potter

[uncleboo]

Hello, Boca. I have an 18 with a Suzuki 140 4 stroke and love everything about it, BUT, the weight. At 436 lbs., it's a lot back there. However, after moving batteries forward and careful weight placement, I use mine with no worries. My biggest problem, I think, is that the boat will fall off plane at around 3000 rpm. I think it's just the excessive weight and possibly the 21 pitch prop I'm running. When the time comes, (meaning money), I'll be doing several changes. I plan on raising the floor, getting all the plywood out, except the transom, and replacing with composite, then moving the console forward about 8". Moving the console has a twofold effect. It'll give me more forward weight to offset the weight of the motor and give me more fishing room. With all that said, I've been to the Gulfstream twice with her and had a ball. Planning on going back soon while the dolphin are getting thick! Good luck with her!

[dave s]

Wasn't there another 18SF here in Boca Raton? I think he was running a older Yamaha 130 and was considering a Suzuki DF140.
That makes at least 3 18s and a lot of 20s.

With all the modifications to my 18 I'm thinking of a 150 Merc or Suzuki.
I fish loaded down and offshore mostly and I want to be able run lower rpms in the slop and cruise in the 30s.

[Vezo, Part II]

My brother has an '87 or '88 Tracker 18 purchased in '96 with an OMC 120. Upgraded to a '95 OMC rebuilt 150. With the 47 gallon tank it would damn near keep up with my '79 MA with a '99 OMC 175, very close to 50 mph boats without gear.

When that engine crapped the bed he went with the 140 Zuke. He is very happy with a little less top end, but significant fuel savings.

My SeaCraft rarely sees the light of day because of the simplicity of my recently sold 1982, refurbished myself in 2005, Boston Whaler Sport 15. Went with an '05 F60, mounted on a Bob's fixed jack plate. She was a 44 mph boat but weighs less than 500 pounds plus 18 gallons of fuel, and a forward mounted 48 qt. cooler.

My next project is an '88 BW sport custom center consul. I have everything I need to rig an F70, minus engine and prop. They're freaking expensive!

As you can see we tend to overpower. But I earned an arse of respect for the etecs this weekend!!! IMHO, I would never contemplate a 70 horse on an 18. Just my two cents.

Vezo, Part II

[BocaSeacraft]

Great information from everyone. It seems we all have different setups aimed at satisfying different needs. We're lucky our Seacrafts are such versatile boats. I'm still on the fence about power. My cousin is a marine mechanic and tells me the F70 is a fine motor with great power to weight ratio. Now, if Yamaha would just run a sale on these things.

[72potter20]

You should consider the new 115 mercury 4 stroke. Pushes my 20sf to 45 mph easily, hit 46.1 with a light load. This with the motor mounted to low and it weighs Less than the new yamaha 4 stroke and much less than the 140 zuke At around 360 lbs

The 150 merc on these hulls would scream

[Vezo, Part II]

I'm not a Merc guy but would have to agree. My ten years with my F60 were flawless minus three broken steering tubes, and I do not trailer far. Of course, my neighbors delivery three weeks ago, I discovered she is "making" oil. Hopefully a bad thermostat causing it to run on enrichener mode. We shall see.?.?.!

[T-MAN]

BocaSeacraft

I just repowered my '76 18' with the new Yamaha 115 a couple of weeks ago. I did not move batteries under the console and wish I had plus I had put a 40 gallon Moeller which I don't regret. She squats a little but not too bad.

I decided before I did anything else I would try putting 50# bag of sand in the front and it helped. I had a Merc 2004 115 hp and I like this new one a lot better.

Good luck

[Bushwacker]

Originally Posted by T-MAN

. . .
I just repowered my '76 18' with the new Yamaha 115 a couple of weeks ago. I did not move batteries under the console and wish I had plus I had put a 40 gallon Moeller which I don't regret. She squats a little but not too bad.

I decided before I did anything else I would try putting 50# bag of sand in the front and it helped. I had a Merc 2004 115 hp and I like this new one a lot better.

Adding ballast is not the best solution. I'd suggest moving the batteries to console and maybe adding 20' of chain to your anchor line, which will dramatically improve holding power of your anchor. And maybe consider adding trim tabs. Any of the Moesly designed SeaCrafts will plane at about 12 mph if balanced right. Other bandaids you could consider to help the stern-heavy condition would be an AV plate fin and a stern lifting 4B prop.

[BocaSeacraft]

I'm still researching the F70 and its use on similar weight boats to my 18. Boston Whalers Montauk 170 weighs in dry at 1400# and the base motor on that boat is shown as a 60 Merc. 90 is max. The more I read about Seacraft 18 and 20' boats and a lot of the advice on this forum stresses weight and center of gravity, etc. If the boats are designed to plane out at 12 mph if balanced correctly, the additional 47-75 pounds of weight (over the design weight of 300#) seen on the latest 90 and 115 four strokes is kind of a big deal. Maybe it's not a big deal if added to the center of the boat, but hanging out over the transom... I'd really like for my scuppers to be above the water line as designed. Maybe I'm crazy but I'm still leaning towards the 265# Yamaha with like a 13 or 14 pitch prop.

[kmoose]

Originally Posted by Vezo, Part II

I'm not a Merc guy but would have to agree. My ten years with my F60 were flawless minus three broken steering tubes, and I do not trailer far. Of course, my neighbors delivery three weeks ago, I discovered she is "making" oil. Hopefully a bad thermostat causing it to run on enrichener mode. We shall see.?.?.!

making oil on a four stroke is an easy fix.... Run it at 5500 for about 10-15 minutes on the way in every trip. Reduces coking as well and keeps everything running well.