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Kiztope

2005 Sunesta 274 8.1 - dog slow.. What's wrong here?

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Hey all,

  I have become the... somewhat proud... owner of a 2005 274 with the 8.1 Gi-F.

All the info I found (which wasnt that much) said that this boat with the 8.1 should do near 50mph.  

The first time I took it out the best I could get was 38 at an rpm under 4k.  I've cleaned the fuel regulators, put in a new fuel filter, changed the plugs, verified new coils (previous owner swapped 5, I did the last 3), cleaned the flame arrestor, new plug wires, ran pure fuel system cleaner through the fuel rail as well as the the normal addition to the gas tank, and have seafoamed the intake.  I also rebuilt the raw sea water pump (new bearing, seals and impeller).  The end result is that it's running smoother, but the top speed is still at 40 with the rpm up to 4100-4200 with just me on board with a 3/4 full gas tank and fresh water tank.  The props are in excellent condition and the hull is glossy and smooth.

The standard size bimini has been up in all testing.  Am I expecting too much?  Any other tips on getting a bit more performance out of this thing?

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1 hour ago, Kiztope said:

Hey all,

  I have become the... somewhat proud... owner of a 2005 274 with the 8.1 Gi-F.

All the info I found (which wasnt that much) said that this boat with the 8.1 should do near 50mph.  

The first time I took it out the best I could get was 38 at an rpm under 4k.  I've cleaned the fuel regulators, put in a new fuel filter, changed the plugs, verified new coils (previous owner swapped 5, I did the last 3), cleaned the flame arrestor, new plug wires, ran pure fuel system cleaner through the fuel rail as well as the the normal addition to the gas tank, and have seafoamed the intake.  I also rebuilt the raw sea water pump (new bearing, seals and impeller).  The end result is that it's running smoother, but the top speed is still at 40 with the rpm up to 4100-4200 with just me on board with a 3/4 full gas tank and fresh water tank.  The props are in excellent condition and the hull is glossy and smooth.

The standard size bimini has been up in all testing.  Am I expecting too much?  Any other tips on getting a bit more performance out of this thing?

Morning.

We'll keep this simple to start:

-How many hours?

-Wide open throttle for this motor is 4200 to 4600 RPM.  There is a range because a handful of props can be fitted.  While you didn't post the drive model number, there should be a pair of stainless duo-props.  Look on each hub and please share the part number or the number that follows the letter F__ on each.  Also, are you closer to sea level or Denver in altitude?

-Time to check compression on each cylinder.  Please write down and share values for each cylinder.  If you need help with how to do this, no problem.  There are a number of people on this forum that can and will guide you.

-Time to check fuel pressure at the rail.  The 8.1 Gi-F specification is 36 to 44, nominal 40.  On the right hand side of the intake, adjacent to the right fuel rail and just past the cross over, there is a pressure regulator.  Please locate it.  Opposite the pressure regulator, on the left fuel rail just before the cross over, is a small vertical valve (it looks similar to a tire valve once the cap is removed, and this type of valve is called a "Schrader" valve).  Please locate it.  This is where fuel pressure is checked, although it might also need to be checked at the fuel pump depending on what we see.

RPM's are slightly less than they should be.  From what you've posted so far, the engine is not in protect mode... thus the need to confirm right props are fitted, engine condition and adequate fuel is reaching the motor. 

This boat should do at least 45 MPH without trouble.  I imagine 50 MPH as well because it's not a heavy boat, like the latter Sunesta's are.

Lastly, please explain what you mean by "it's running smoother".  When reading this statement it makes me think it's running better, but not smooth like it should be.

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It may be something a simple as trying a new set of props. Like Curt mentioned, what pitch are you currently running?

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Thanks for the reply!

Hours: 175

Props: f5rear 3851475 5b, f5front 3851465 5b

Altitude: 680ft above sea level

I'll be checking the pressure at the fuel rail today. (The loaner gauge I got the other day has a broken connector... :( )

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two things, are you using your trim well? Are your speeds GPS? My speedo is off by 10MPH 40 is 50 mph My tach is off too.  Verify your speed first 

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35 minutes ago, cyclops2 said:

Check your GPS speed using a car.

??????

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4 hours ago, Kiztope said:

Thanks for the reply!

Hours: 175

Props: f5rear 3851475 5b, f5front 3851465 5b

Altitude: 680ft above sea level

I'll be checking the pressure at the fuel rail today. (The loaner gauge I got the other day has a broken connector... :( )

Suggest checking cylinder compression as well.  Unless neglected or abused, should be fine.  175 hours is nothing.

If fuel pressure, cylinder compression and Baja's suggestions all checkout, a set of F4's will increase RPM's something like 200 but not sure this gets 45 + given current experience/situation. Then there's cost.  Duo Props are expensive even if you happen across a one-off set on CL or eBay, or a local prop repair shop happens to have a reconditioned/repaired set.  F4 part numbers are 3851464 and 3851474.

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If the power train checks out well and you decide to change props give the guys at Hill Marine a call. They will dial you in and have a great return policy if you need to try a couple different sets.... 

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I'm using GPS for the speed, adjusted the trim to get it smooth (as level as possible).

I just checked fuel pressure...  It's a solid 6-8 on the low side and on the high side the needle flickers constantly between 35 and 50.

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23 minutes ago, Kiztope said:

I'm using GPS for the speed, adjusted the trim to get it smooth (as level as possible).

I just checked fuel pressure...  It's a solid 6-8 on the low side and on the high side the needle flickers constantly between 35 and 50.

Thank you. Did you check at the fuel rail also? If not, that’s the next step. 

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Something's not right.  Same motor with F6 props in my Crownline 270 BR, which is 900 pounds heavier than your boat, turns 4600 RPM at about 51-52mph with full fuel and 6 adults in it.  The Sig 276 I just bought with the same motor, spinning F5 props at 4650, full fuel and 4 adults hits 44mph and it's 7500 pounds.  I can't imagine hull design would be holding you back that much.......

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1 hour ago, Curt said:

Thank you. Did you check at the fuel rail also? If not, that’s the next step. 

The high side I was referring to was at the rail

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51 minutes ago, Johnfrmcal said:

Something's not right.  Same motor with F6 props in my Crownline 270 BR, which is 900 pounds heavier than your boat, turns 4600 RPM at about 51-52mph with full fuel and 6 adults in it.  The Sig 276 I just bought with the same motor, spinning F5 props at 4650, full fuel and 4 adults hits 44mph and it's 7500 pounds.  I can't imagine hull design would be holding you back that much.......

I agree!!!  I think it's performing like a pile of poo! 

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20 minutes ago, Kiztope said:

The high side I was referring to was at the rail

Thank you.

To start, you’ve confirmed a bad fuel module. Three options:

-Replace entire module with new.

-Replace high pressure pump and rebuild balance of the module yourself.

-Send out for complete rebuild.

As to the last two options, Hatem (another blog participant) found a guy on the web that offers a DIY video and rebuild service. Unfortunately, I don’t recall his name.

To establish a baseline going forward, a cylinder compression check is still suggested. Doesn’t cost anything and doesn’t take much time.

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Curt , was it the fluctuating fuel pressure that confirmed it? 

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8 minutes ago, Phillbo said:

Curt , was it the fluctuating fuel pressure that confirmed it? 

Phil,

Afternoon. Yes, in part. Typically it’s steady to a few pounds of light flutter. Jumping between 35 and 50 isn’t, and the low and high are being exceeded.

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Hmmm...  Thanks for the info!  I've got a compression test tool that I'll throw on tomorrow. 

I also want to give another fuel pressure gauge a shot before dropping the coin on a fuel pump (those suckers ain't cheap!!!)  The one I have is brand new $50 Bosche and I'm not sure I trust it yet. 

If anyone remembers the guy that does the rebuilds, I'd be grateful! There is an aftermarket replacement pump on Amazon for near 200, but it appears to be for the 5.0/5.7, not a replacement for 21608512.  I'd like to pick up a cheap replacement while the other gets rebuilt.

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6 minutes ago, Kiztope said:

Hmmm...  Thanks for the info!  I've got a compression test tool that I'll throw on tomorrow. 

I also want to give another fuel pressure gauge a shot before dropping the coin on a fuel pump (those suckers ain't cheap!!!)  The one I have is brand new $50 Bosche and I'm not sure I trust it yet. 

If anyone remembers the guy that does the rebuilds, I'd be grateful! There is an aftermarket replacement pump on Amazon for near 200, but it appears to be for the 5.0/5.7, not a replacement for 21608512.  I'd like to pick up a cheap replacement while the other gets rebuilt.

Definitely a good idea to test again. Always best to have confidence in your tools.

If I recall correctly, the 5.0/5.7 pump is different. I’ll check and confirm in the morning for you.

Suggest passing on the cheap knockoff route. Not much worse than paying and having to do it again, again...

For the repair guy, search on the blog, web or perhaps @Hatem will chime in.

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19 hours ago, Kiztope said:

Hey all,

  I have become the... somewhat proud... owner of a 2005 274 with the 8.1 Gi-F.

All the info I found (which wasnt that much) said that this boat with the 8.1 should do near 50mph.  

Curious where you got this information from?  Sales pitches for similar boats online or actual testimony from people who own that particular boat around the same year with the same engine?  I tried looking up the PDF for your boat and engine combination but only found it with a Mercruiser.

9 hours ago, Johnfrmcal said:

Something's not right.  Same motor with F6 props in my Crownline 270 BR, which is 900 pounds heavier than your boat, turns 4600 RPM at about 51-52mph with full fuel and 6 adults in it.  The Sig 276 I just bought with the same motor, spinning F5 props at 4650, full fuel and 4 adults hits 44mph and it's 7500 pounds.  I can't imagine hull design would be holding you back that much.......

Those are some pretty incredible numbers for a Signature 276, wow good for you.  Your F6's are probably what are pushing you up that high.  My 276 ssx with 8.1Gi-J (although I have never pushed it to WOT) but just the other day I was out alone in some pretty glassy ocean water with is very unusual for us on the ocean, with a full tank of gas and bottom paint and I reached 47mph.  I did  notice that I still had about another inch or so to go with the throttle but I chickened out which tells me that even with my F-5's, I should be able to reach 50mph, maybe even a bit more if I didn't have bottom paint.  I even added quite a bit of weight to the bow with my new windlass anchor I installed myself.

But I do think that the older Sunestas like the OP's which had a hull design with an 18 degree deadrise  probably did limit speed quite a bit.  There's a reason why they changed it to the newer style with much greater deadrises.

This is a 97 Sunesta front end and granted it's about 8 years older than the OP's, but I'm not sure Chap changed this hull design much until they went to the completely new design and this is not exactly what I -- or anyone for that matter -- would define a water-cutting design compared to all our new V-hulls.  So the fact that the OP is getting the newer numbers (even with a VP 8.1) is pretty darn good.

08590558-8ED6-421F-9F58-D6245A3B13FA.jpeg

 

20 hours ago, Kiztope said:

The first time I took it out the best I could get was 38 at an rpm under 4k.  I've cleaned the fuel regulators, put in a new fuel filter, changed the plugs, verified new coils (previous owner swapped 5, I did the last 3), cleaned the flame arrestor, new plug wires, ran pure fuel system cleaner through the fuel rail as well as the the normal addition to the gas tank, and have seafoamed the intake.  I also rebuilt the raw sea water pump (new bearing, seals and impeller).  The end result is that it's running smoother, but the top speed is still at 40 with the rpm up to 4100-4200 with just me on board with a 3/4 full gas tank and fresh water tank.  The props are in excellent condition and the hull is glossy and smooth.

The standard size bimini has been up in all testing.  Am I expecting too much?  Any other tips on getting a bit more performance out of this thing?

Next time you try her out, take that bimin off completely!  Those style biminis on those boats are like parachutes.  They're not the same like what we have which extend off the back of the radar arch and even that I had it off when I did my test and now it's up and I notice a difference.

if you cleaned the fuel regulators, put in a new fuel filter, changed the plugs, verified new coils (previous owner swapped 5, I did the last 3), cleaned the flame arrestor, new plug wires, ran pure fuel system cleaner through the fuel rail as well as the normal addition to the gas tank, and had seafoamed the intake, also rebuilt the raw sea water pump (new bearing, seals and impeller) and the end result is that it's running smoother, but the top speed is still at 40 with the rpm up to 4100-4200 with just you on board with a 3/4 full gas tank and fresh water tank and the props are in excellent condition and the hull is glossy and smooth, I would say that your problem is in a few other minor adjustments.  Did you check all the gapping on all the new plugs?  If you went from under 4KRPM to 4200RPM with just that bit of tuning up, I would say the rest of what you need to do is minor.  checking if your low and high pressure pumps are performing to their maximum might be the next step.  A compression test is pain in the $^& and if you were really underperforming, I would say yes go through that trouble but if you're at 4200rpms in the current state,  I doubt you have a compression issue but I could be wrong.

What outdrive are you using?  When was he last time you had it off an inspected it?  Changed oil and checked the old for any metallic shavings?

Here's the guy who fixes the Volvo fuel pumps for really cheap money.

Part 1

 

PART 2

 

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Less deadrise is almost always the faster LOADED boat.

Steeper deadrise number is a slower boat. But a softer riding boat.

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52 minutes ago, cyclops2 said:

Less deadrise is almost always the faster LOADED boat.

Steeper deadrise number is a slower boat. But a softer riding boat.

 Did I confuse the two?  Isn't the sharper the V hull, the faster?  

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13 hours ago, Kiztope said:

Hmmm...  Thanks for the info!  I've got a compression test tool that I'll throw on tomorrow. 

I also want to give another fuel pressure gauge a shot before dropping the coin on a fuel pump (those suckers ain't cheap!!!)  The one I have is brand new $50 Bosche and I'm not sure I trust it yet. 

If anyone remembers the guy that does the rebuilds, I'd be grateful! There is an aftermarket replacement pump on Amazon for near 200, but it appears to be for the 5.0/5.7, not a replacement for 21608512.  I'd like to pick up a cheap replacement while the other gets rebuilt.

 

13 hours ago, Curt said:

Definitely a good idea to test again. Always best to have confidence in your tools.

If I recall correctly, the 5.0/5.7 pump is different. I’ll check and confirm in the morning for you.

Suggest passing on the cheap knockoff route. Not much worse than paying and having to do it again, again...

For the repair guy, search on the blog, web or perhaps @Hatem will chime in.

Kiztope,

Closing the loop. 

-The 5.0/5.7 pump is different.

-Hatem chimed in with the web guy.  Suggest checking it out.

-Also, happened across an owner with your boat and a Volvo Penta 5.7L, 280 horsepower.  Their top speed is 45.  Considering your motor has 95 more horsepower but slightly heavier, 45 is certain and 50 should be possible with a properly operating engine and good water conditions.  Thought you might be interested in a real comparison.  

Best.

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2 hours ago, Hatem said:

 Did I confuse the two?  Isn't the sharper the V hull, the faster?  

Yah, you confuzed it. Flatter hull (less deadrise) has less drag as is thus typically faster than equivalent vee with more deadrise.

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