258 with big block?

Haddock_ · **Posted:** Fri Aug 08, 2014 2:10 pm

Hi

I'm kinda toying with the idea of a 8.1L engine in my '06 258. Anyone done it? What were the gains vs the 5.7 320hp?

The reasons are
1) I have the money, rest of the boat fits us fine
2) greater cruising speed range, economy 25-30 mph with lower consumption than today or "fast cruise 35 mph plus" with I guess similar consumption as today. At the moment its a kinda limited spread. We do a lot of fast cruise transportation.

Mike

rpengr · **Posted:** Fri Aug 08, 2014 2:40 pm

I'm not a big believer in the "Bigger engine uses less gas" theory (Myth).

Here why:
Lets say it takes 175 horsepower to push your boat at 25mph. Both size engines are going to consume almost exactly the same fuel to produce 175 horsepower.

However, the smaller engine will be more inefficient when near the top of it's power range (275-320 hp) because it is dumping in extra gas to make it there. The bigger engine should use less gas at those power settings, but of course will use even more at it's high power settings.

The larger engine will also use more gas while idling, but that's usually not much of a concern.

That being said, if you have the money and you like the fast cruise, then go for it. It should be good for resale value also. Just don't expect to use less gas.

ric · **Posted:** Fri Aug 08, 2014 2:48 pm

Before I bought my Chaparral I almost purchased a 1998 258 Vista that was repowered with a 8.1gi dual prop.

IT WAS f***ing AWESOME!!!!!!!!!!!!!!!!!!!!!!! Power for days!!!!!!!! I really wish I bought it, but at the time I had nowhere to put it.

Easy math. Look at the 2005 268 Vista.
8.1 = 30mph 12gph
5.7 = 31mph 14gph

Paul I. · **Posted:** Fri Aug 08, 2014 3:11 pm

I would save the $$ and go with another boat. You must be talking about 15 to 20 k to do this.

I had a 2006 V258, the wiring in the boat was nothing but trouble. They don't use marine wire when the built it.

ric · **Posted:** Fri Aug 08, 2014 3:14 pm

Paul I. wrote:

I would save the $$ and go with another boat. You must be talking about 15 to 20 k to do this.

I had a 2006 V258, the wiring in the boat was nothing but trouble. They don't use marine wire when the built it.

Well, considering you can buy a 268 Vista with an 8.1, genset, AC... I would just sell your 258 and buy a 268 already ready to go. On average they're going for around 40k.

Graham R · **Posted:** Fri Aug 08, 2014 4:42 pm

Paul I. wrote:

I would save the $$ and go with another boat. You must be talking about 15 to 20 k to do this.

I had a 2006 V258, the wiring in the boat was nothing but trouble..

They perfected the problems with 2009 boats. Nothing to do with untinned wire ! Bizarre wiring problems.

ric · **Posted:** Fri Aug 08, 2014 4:58 pm

Graham R wrote:

Paul I. wrote:

I would save the $$ and go with another boat. You must be talking about 15 to 20 k to do this.

I had a 2006 V258, the wiring in the boat was nothing but trouble..

They perfected the problems with 2009 boats. Nothing to do with untinned wire ! Bizarre wiring problems.

After 2009 did Four Winns actually start using watertight automotive connectors and common ground blocks?

Graham R · **Posted:** Fri Aug 08, 2014 5:12 pm

ric wrote:

Graham R wrote:

Paul I. wrote:

I would save the $$ and go with another boat. You must be talking about 15 to 20 k to do this.

I had a 2006 V258, the wiring in the boat was nothing but trouble..

They perfected the problems with 2009 boats. Nothing to do with untinned wire ! Bizarre wiring problems.

After 2009 did Four Winns actually start using watertight automotive connectors and common ground blocks?

Oh yes, the connectors are now very good indeed, all waterproof. It's the unseen, unrecorded connections and bizarre connections that let them down,

Haddock_ · **Posted:** Sat Aug 09, 2014 1:03 am

I live in a part of the world where supply is thin...not much to chose from!

Going volvo to volvo, gxi to gxi...I dont expect a lot of wiring changes?

I expect economy cruise rpms to be at least 500 rpms less i.e should be more frugal? At the moment I'm getting just shy of 2mpg and not reaching top speed, so the current motor is "tired" at 450 engine hours. 8.1's pop up second hand fairly often as people convert to diesel.

Will the DP-S drive work?

meinmelb · **Posted:** Sat Aug 09, 2014 1:13 am

Haddock_ wrote:

I live in a part of the world where supply is thin...not much to chose from!

Going volvo to volvo, gxi to gxi...I dont expect a lot of wiring changes?

I expect economy cruise rpms to be at least 500 rpms less i.e should be more frugal? At the moment I'm getting just shy of 2mpg and not reaching top speed, so the current motor is "tired" at 450 engine hours. 8.1's pop up second hand fairly often as people convert to diesel.

Will the DP-S drive work?

I would not considder 450 hours "tired". Those 5.7 blocks are the same as used in the waterski / wakeboats and run to about 2000 hours before being considered for replacement. Our last club boat used the 5.7 and ran nearly 3000 hours before we sold it to a member and it is still running.

Perhaps salt water might damage other components but I doubt it makes any difference to long term performance inside the motor if maintained properly.

Personally there is no such thing as too much power..... In fact too much power is just about enough....! So upgrade and post a photo of your grin at WOT!!

Rick2752 · **Posted:** Sat Aug 09, 2014 6:46 am

If you have money to blow have at it, but you can't call it fuel economy. Let's say you get it done for 10k. I think that's a pretty low number but I don't know how much work you are able to do. 10k divided by 2 gal per hr savings on fuel at 5 bucks a gallon. So you save 10 bucks per hr you run the boat. It has 450 on it now so when your boat hits 1450 hrs, you will break even. How long did it take you to put 450 hrs in it? If you want the fuel economy add fuel monitor like bliss has. Install auto trim tabs to always run at efficient levels. Probably could upgrade the flame arrester. There may even be a chip out there, I haven't looked. I just don't view my vista as a go fast boat. Good luck and if you do it post some photos. If you decide to do it, go out and record some concrete data how the boat does before and after the swap

Haddock_ · **Posted:** Sat Aug 09, 2014 7:19 am

Thanks for the encouragement!

I have a fuel metering monitor, at 25 knots cruise boat consumes 60l/nm give or take a little depending on waves and how any we are, fluids on board etc. Because of the meter, I constantly work the tabs and trim to optimise as I see it as a bit of fun to be as frugal as possible.

I havent found any solid mechanics I trust who will give me honest advice if the motor is going or some kind of issue making it perform less than optimal, as the tired, disengaged (!) advice I get is to do a head/valve job which in cost is nearly the same as the hours to pull engine and replace with new (like for like)...

Anyway, just tossing the idea around and just wanted your thoughts

rpengr · **Posted:** Sat Aug 09, 2014 8:18 pm

Haddock_ wrote:

Going volvo to volvo, gxi to gxi...I dont expect a lot of wiring changes?

The wiring should be much the same.

I think they are referring to wiring problems in the rest of the boat to be a common issue with some Vista's

Haddock_ wrote:

I expect economy cruise rpms to be at least 500 rpms less i.e should be more frugal? At the moment I'm getting just shy of 2mpg and not reaching top speed, so the current motor is "tired" at 450 engine hours. 8.1's pop up second hand fairly often as people convert to diesel.

Will the DP-S drive work?

You will have to be a least 500 rpm less to balance out the extra displacement...and therefore use the same amount of fuel... no savings.

People probably convert 8.1's to diesel often because they use so much fuel. Diesel is the only way to get better economy, but it takes a much higher purchase cost that most recreational users would probably never get to the break even point.

DP-S drive should be fine with the 8.1

Haddock_ wrote:

I have a fuel metering monitor, at 25 knots cruise boat consumes 60l/nm give or take a little depending on waves and how any we are, fluids on board etc. Because of the meter, I constantly work the tabs and trim to optimise as I see it as a bit of fun to be as frugal as possible.

I havent found any solid mechanics I trust who will give me honest advice if the motor is going or some kind of issue making it perform less than optimal, as the tired, disengaged (!) advice I get is to do a head/valve job which in cost is nearly the same as the hours to pull engine and replace with new (like for like)...

Anyway, just tossing the idea around and just wanted your thoughts

I can't make any sense of the 60l/nm number. Wouldn't that be about 0.07mpg?

I agree with the others that 450 hours should not be tired at all, normally. 2000-3000 hours should be achievable. However, there are some circumstances where valve damage can occur when an engine is "overpropped" (too much pitch, not achieving high enough wide open throttle RPM). So your mechanics may be right to suggest head rebuilds. Search "Tulliped Valves" for more information about this.

Ray

Haddock_ · **Posted:** Sun Aug 10, 2014 8:11 am

Thanks - will research head issues

The 60l/nautical mile was a typo, I meant 60l per hour, which is like 16 gal per hour if my maths is correct... I believe that is on the high side for 27-28mph cruise indicating "something" isnt fully right. At the seasons end I will empty gray and fresh water tanks and all the other extras and see what it does "unloaded".

ric · **Posted:** Sun Aug 10, 2014 9:01 am

450 hours?? It's still brand new. I wouldn't consider a chevy small block "tired" until you're past the 3000hr mark.

Your lack of performance is most likely due to water absorption in the hull.

www.iFourWinns.com

258 with big block?

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