285SSi won't break 43 mph or 4100 rpm

[ChappedAss285]

Hi everyone,

I have a 2002 with twin 350 Mags/bravo III's and stock props. As stated above it cant reach maximum speed. I have, in the past, had it to about 53 mph. It runs well throughout the whole range of rpm's included full throttle, but I have noticed that it falls flat the last %20 of throttle travel. It doesn't bog or run poorly, it just doesn't accelerate or increase rpm's.  I haven't had the time to completely investigate yet, I just found out today.

Please share some thoughts if you can.

Thnx

[Bt Doctur]

carb`d, injected, past service records, tune-up. fuel pressure, etc

[ChappedAss285]

injected. all service records done by same marina for life of boat. all engine and outdrive recommended service has been done with a stack of paperwork. Nothing major has been replaced and boat is in great condition.

Don't know fuel pressure but had both mechanical and hull inspected before purchase in Oct 2017. I am second owner. 650 hrs currently on motors. Tune up and gimbal bearings done at that time as well. Compression was great and, according to mechanic, very well kept up. 

[cyclops2]

Accurate GPS or dash speedo ?

[Quag]

I am interested in this too.  Much different set up, but put a 19 pitch prop and not coming close to WOT.  Runs great through out the range and reach WOT with a 17 pitch.

[jd50i]

I had a similar problem on another boat, it was not fully advancing the timing. Run great just would get full power.

[Phillbo]

Since both engines are experiencing the same issue i'd lean towards a dirty hull. Is it a slip queen or trailered? 

[cyclops2]

I am with Phill.  

Do you adjust both drive trims for highest speed ?

[ChappedAss285]

GPS says 43 mph at 4100 ish rpm. I adjusted both trims to get there. Trim tabs all the way up and then had to slightly raise motor trim until it maxed out and started porpoising.

I keep it on a canal behind house. I just had bottom acid washed, rubbed out and waxed first week of june,  and cleaned hull in the shallows first week of July. It will get some algae build up within a few weeks. Maybe I will pull her out and look closer. I usually wash it in the shallows as soon as the dreaded green waterline starts appearing. I am gonna eat some gas and refill with non ethanol 91. It just dawned on me that I filled up last Tuesday with 87 that wasn't ethanol free. I told dock chic to give me $100 and she filled it up :/.

Im in the middle of moving to a new home and updating my current home to sell, so my time to spend on boat has been precious and minimal. I will try some suggestions this Sunday, hopefully. It's my youngest daughters grad party this weekend as well.....

Thnx!

 

[cyclops2]

If both engines are 4100 rpm ?   Bad load of gasoline. Only thing that can affect both.

Or clogged up fuel / water separator.  But I would expect some bucking / backfiring in a carbed boat. Maybe the EFI can mask insufficient fuel delivery ?

Check fuel pressures at WOT.  Might get lucky with bad fuel filter ?

[brick]

My vote is a dirty bottom. 

What RPM @ WOT do you see when it is running correctly?

brick

[Hatem]

12 hours ago, ChappedAss285 said:

I  just had bottom acid washed, rubbed out and waxed first week

If you get her out onto a trailer, you should try pressure washing the bottom.  Works much better than using acid or whatever chemicals.  High water pressures blasts that crap off really nicely and saves you all that elbow grease.  Just be careful when you do it around the drives. 

You actually wax the bottom?  If we put the boat in the slip in mid-May, by the 2nd week of July you can start seeing a bit of growth, even in these much cooler, ocean waters up this way.  Our boat is usually humming earlier in the season and gets pretty bogged down by August.  I'm actually thinking of pulling her out in a couple of weeks and give the bottom a quick pressure wash instead of waiting until the end of the season when all the growth is all caked on.  Those barnacles are a #$%$&$% #$%&%$ #%&*%^!

[soldier4402]

for both engines to go down like that is weird, hull would be my first guess.  Non ethanol fuel specially if its fresh as in less than a month old, I wouldn't look to much into, phase separation takes at least a week.

[cyclops2]

I thought Phase Separation was occurring between a high and low percentage points of moisture in the gasoline.

[ChappedAss285]

I do the pressure wash in between. Acids wash is just because I just got it in October 2017 and it was delivered and stored. Needed a little boost cuz pressure washer wouldn't clean it back to original color.
I have had it o 54 mph and I think that was 4800ish rpm. Haven't had it out that much yet.

[Mi3sons]

My buddy had one with the Volvo 5.7's and would run up to57-58.

[Hatem]

14 hours ago, ChappedAss285 said:

I do the pressure wash in between. Acids wash is just because I just got it in October 2017 and it was delivered and stored. Needed a little boost cuz pressure washer wouldn't clean it back to original color.
I have had it o 54 mph and I think that was 4800ish rpm. Haven't had it out that much yet.

Ah, ok.  I don't know how bad fresh water growth is, but salt water is horrible!  It's more than some type of vegetation, it's mostly barnacles and they are a SOB to get off and you can imagine a clean hull that's suddenly filled with what is essentially shells sticking out from it!  It becomes like sandpaper.

The other thing that freaks me out is you guys with 28+ft boats doing 55mph.  That is insane.  I get up to 35 and I feel like I'm going to die with one wrong move.  You must have glassy water conditions on those lakes to get to those speeds in the 50's?  We'll be lucky to see glassy ocean up our way maybe once or twice the whole season and you need to be really lucky that it happens when you're out there.

What's the exact length of a 285ssi? 

[cyclops2]

To be honest. I prefer going + 50 mph in larger boats. Almost 50 mph in a WW II destroyer was a very secure ride.

[Hatem]

5 minutes ago, cyclops2 said:

To be honest. I prefer going + 50 mph in larger boats. Almost 50 mph in a WW II destroyer was a very secure ride.

Mmmm.... I can see the similarity of a 29ft 285ssi made of a fiberglass hull weighing about 8000lbs to a WWII destroyer that's around 500ft in length of solid steel with an average displacement of 9000 tons? lol.

[cyclops2]

 

  We were small at 300'. 2,100 tons & over 60,000 shaft hp. 

How much hp do the modern offshore boats pack ?