Anyone have SF with under gunnel air intakes?

[madhatter1]

We get soot on the transom and in the cockpit areas over time. Was looking into mechanical issues and tune up but decided that's probably not the issue. Engines (8-92TI's) start with no smoke and run super clean. Zero visible exhaust on plane. Clean air filters, intercoolers, and good turbo's.

But we still get the soot buildup on the paint. If we go into a strong headwind it builds up quicker. Calm days or wind behind us much less. Also we get salt mist spray in the same areas more in head wind and less in tailwind.

So basically seems like a big station wagon effect compounded by the under gunnel air intake. Not sure if the amount of air drawn into ER is enough to be a factor. Also we have a full 4 sided enclosure with no openings ion the back other than ladder area.

Wondering if others experience the same. Most SF's have the ER vents on the side. Guessing responses will be limited.

 

[Wiredup62]

My 60 GT has the under gunnel vents and no vents along the outside of the hull. I have not had any issues, but the CAT C32 acerts don't smoke much anyway.

 

[racclarkson@gmail.com]

We get soot on the transom and in the cockpit areas over time. Was looking into mechanical issues and tune up but decided that's probably not the issue. Engines (8-92TI's) start with no smoke and run super clean. Zero visible exhaust on plane. Clean air filters, intercoolers, and good turbo's.

But we still get the soot buildup on the paint. If we go into a strong headwind it builds up quicker. Calm days or wind behind us much less. Also we get salt mist spray in the same areas more in head wind and less in tailwind.

So basically seems like a big station wagon effect compounded by the under gunnel air intake. Not sure if the amount of air drawn into ER is enough to be a factor. Also we have a full 4 sided enclosure with no openings ion the back other than ladder area.

Wondering if others experience the same. Most SF's have the ER vents on the side. Guessing responses will be limited.

I got some high hour Detroit 71's, and mine intake under the cockpit coaming as well. But, I've not experienced sooting around the transom.

 

[madhatter1]

Maybe Its just the 46 design. I wanted to dig into injectors and tuning and such but my mechanic questioned why on perfectly clean running engines. And he is not the kind of guy who would turn down work. I run kind of slow at 22 MPH when it can run 26-27 MPH all day long. Cruise at 1750-1800 RPM's. Maybe I should run them at 1900 to burn a little hotter and cruise faster. Strange since they run so clean by the eye.

 

[madhatter1]

Just to clarify when I say soot i mean stains in paint that wash right off with spray-9. Not actual heavy soot buildup.

 

[pdog]

My 46 has under gunnel air intakes as well. I have had zero issues with soot on transom. I do get the mist at times depending on wind direction.

 

[madhatter1]

Perhaps I do need to address this from a mechanical standpoint. Just seems odd with the exhaust so clean to the eye. Thanks for the responses. Answered my question.

 

[rsmith]

Hatteras went to the cockpit combustion air intakes when salt ingestion became a problem. Most of the convertibles were hard fished in the day. Beating your way offshore to the offshore canyons would result in spray getting sucked into the intakes. I delivered several 46’s to Ben Hurley back in the day for the Hurley treatment one of his most popular mods was eliminating the side vents and adding cockpit intakes. I think Hatt went back to the side vents because of engine room noise being transferred into the cockpit. I understand the new vents are much larger and slow the velocity of the air coming in to give the spray a chance to drop out in the plenum box. As far as soot as long as there is no smoke behind the boat when your running just run it. Could be crappy fuel also. I’ve had loads of fuel over the years that smoked more than others. Who knows what’s going on at the refinery. We used to spend the month of June at Marsh Harbor. Fished 25 days back to back. The fuel there was clear as gin and burned cleaner and the boat preformed better than it ever has. Fuel guys said that their fuel came from Venezuela. I never really considered before where the oil came from and how it was refined.

 

[madhatter1]

Robert, what is your opinion on servicing fuel injectors. As far as I know these are original from Dave's install on the new engine (950 hours) and the in frame rebuild (850 hours). I know injectors were done on the rebuild because original issue was an injector issue.

And yes, downside to air intakes is engine room noise. The generator sound is loud enough in the cockpit to be irritating when on the hook.

 

[racclarkson@gmail.com]

Robert, what is your opinion on servicing fuel injectors. As far as I know these are original from Dave's install on the new engine (950 hours) and the in frame rebuild (850 hours). I know injectors were done on the rebuild because original issue was an injector issue.And yes, downside to air intakes is engine room noise. The generator sound is loud enough in the cockpit to be irritating when on the hook.

Easy question. Consult the injector guru Derek a/k/a Avenger on the forum.

 

[finatic]

I have a 1984 52c with under gunnel air intakes and have never had an issue.

 

[Avenger]

Mr. Smith brings up an excellent point. We had the local Volvo dealer buying quite a bit of additive because after they did major tune-ups on some of those notorious smokers they'd still get a slight amount of transom sooting and the additive was the last piece of the puzzle. Fuel quality has a lot to do with combustion quality and injector life.

The fuel quality standard in the US is quite low and we're seeing reduced injector life because of it. In addition our customers are seeing improvements in fuel efficiency and cleaner exhaust when using additive.

 

[Avenger]

Injector service intervals are a little more challenging since so much depends on the quality and amount of fuel that goes through them. Unfortunately, nobody brings them to us and tells us how many hours are on them.

When I was at Lucas/Delphi training their comment was the life of one of their injection pumps is about a tablespoon of dirt. You could do that over twenty years, or twenty minutes. Your call.

I'd look at the manual and see if DD has a recommendation. If not maybe 1000 hrs might be a good time to have them checked, but they should last much longer than that. Or just go with, "If it ain't smokin' it ain't brokin'." Many people keep them running until there is an issue and I can't say they're wrong either.

 

[Jim saco]

We get soot on the transom and in the cockpit areas over time. Was looking into mechanical issues and tune up but decided that's probably not the issue. Engines (8-92TI's) start with no smoke and run super clean. Zero visible exhaust on plane. Clean air filters, intercoolers, and good turbo's.

But we still get the soot buildup on the paint. If we go into a strong headwind it builds up quicker. Calm days or wind behind us much less. Also we get salt mist spray in the same areas more in head wind and less in tailwind.

So basically seems like a big station wagon effect compounded by the under gunnel air intake. Not sure if the amount of air drawn into ER is enough to be a factor. Also we have a full 4 sided enclosure with no openings ion the back other than ladder area.

Wondering if others experience the same. Most SF's have the ER vents on the side. Guessing responses will be limited.

I get the same results on my 41. Especially with a strong headwind as you’ve described. I’ve always blamed it on the cockpit air intakes pulling exhaust back into the cockpit.

 

[madhatter1]

My tanks and fuel are so clean I never see any hint of goop or water in the Racor bowls. In fact the seals started to leak since it had been so long since they were serviced other than filter changes. The guy they sent thought they had just be cleaned recently.

But I guess that has nothing to do with fuel quality. We buy from local municipal marina that does plenty of volume. What additives are good to use? of volume.

 

[ageless]

Have you run load numbers? What's your engine temps? Possibly overloaded?? I use the Opti-lube Summer because the volume to ratio is AMAZING and my fuel is pretty clean with all the injectors in my 12/71's rebuilt by RPM in the last year, so worth it to have the assurance there's no reliajunk injectors in my ER

I have cockpit intakes and had soot when I was overloaded, after the injectors were done and I was 100% there was nothing mechanical I was 250 star/400port overloaded that I fixed with prop service. Soot gone

 

[madhatter1]

Engines make full RPM's. Going to try the Stanadyne additive recommended by Avenger. Since everything else is presumed correct the fuel quality issue seems like a real possibility. There is a 35 Bertram SF charter boat out of the marina I fuel up at (they do too) that is has a very soot stained back half. It has Cummins 330 6BTA's and I never see any smoke from it on or off plane. In any case the fuel additive cant hurt. Tank is half full now so I'll put in enough to treat the full tank capacity and fill up. Then I ordered 16oz bottles that treat 65 gallons each so I can add as I refill easily. We will be running around locally all summer and this fall we run 100 miles south to Captiva. So that will put plenty of treated fuel through the engine first and then we shall see on the trip..

 

[rustybucket]

Mr. Smith brings up an excellent point. We had the local Volvo dealer buying quite a bit of additive because after they did major tune-ups on some of those notorious smokers they'd still get a slight amount of transom sooting and the additive was the last piece of the puzzle. Fuel quality has a lot to do with combustion quality and injector life.

The fuel quality standard in the US is quite low and we're seeing reduced injector life because of it. In addition our customers are seeing improvements in fuel efficiency and cleaner exhaust when using additive.

Curious, what additives were being used?

 

[Avenger]

Curious, what additives were being used?

In that case they were buying Stanadyne.

Alliant Power is a comparable product. There are other good additives out there, but those are the ones we recommend because those are the ones where we have first-hand experience.

Bottom line, no matter who's fuel you are buying you need to use an additive. If you're burning home heating oil you need a lot of additive.

 

[rsmith]

Don’t confuse fuel contamination with low quality. Doesn’t mater where you buy it it’s where it was refined. My son a combat pilot did 7 deployments in Afghanistan at Bagram AFB all the jet A and diesel we used there came from Russia. Their our enemies no? He used to say the jets smoked like crazy and the exhausts would coke up with carbon. Not exactly what you want for stealth operations