Exhaust fumes

[Jim Hardesty]

Today I motored for a long time.  The exhaust smell was fairly strong, so I opened the dodger window, better but still there.  Opened the side window to dodger and better but still minimally there.  Finally, I folded the bimini back and Voila, 100% clean air.

Unfortunately this a terrible solution on most days; for lack of sun protection  from the bimini on sunny days and on colder days will have to keep the window closed.

Must be a way to divert the fumes elsewhere.

Here's an idea, if you have straps that adjust the angle/position of the bimini.  Experiment with adjusting as far in each direction as reasonable and see if it helps.  Do you have a filler between the dodger and bimini that may change things.
Because you experience fumes more than others I'm thinking that possibly it's the fit/cut of your canvas.
Jim

[scgunner]

Tom,

Back to initial factors that may not have been considered. Are there any add ons at the rear like a dinghy hanging on davits or solar panels mounted on the back railing or even something as seemingly insignificant as a BBQ or an OB mounted on the rail? There has to be something back there that's creating a low pressure area behind the transom which allows exhaust fumes to be drawn back to the boat. You confirmed that the exhaust outlet is in the correct factory location is that location on the bottom of the hull pointing down about a foot or so ahead of the transom?

[Jim Hardesty]

A couple of days ago I was crossing Lake Erie, motoring, and the wind was 7 knots right behind me.  Didn't have much else to do so was thinking of your problem, was a few sniffs of fumes.  Got out my portable 12 volt fan, Cafamo, and adjusted it to blow towards the stern.  It seemed to work on the few fumes I was getting.  An hour or so later the wind built and shifted, had a great sail into Port Dover, Ontario.  Of course the fan was put back.
Jim

[Ron Hill]

Guys : It appears that it is the Bimini that is the culprit, causing exhaust fume to enter the cockpit. My Bimini height is just below the split in the backstay. I usually have the Bimini up (no connecting piece to the Dodger - except for rain) with the center window of the dodger OPEN ( tied up under the dodger).
 
Our dodger height is such that Standing at the wheel - I can see over the dodger and 1st Mate can see under the dodger!!

I've NEVER experienced exhaust fumes - maybe my engine just doesn't have "Bad Breath"!!   

[rjabara]

I think that is right.  The only thing that is still puzzling is that for tmac and me, it is most noticeable going INTO the wind, which to me is counterintuitive.  I'm going to test scgunner's suggestion above, which is to remove my port perch seats and the bbq also on the port side, perhaps it is getting "stuck" there and finding its way into the cockpit.

[tmac]

Sorry that I've been unresponsive.  I got nailed with Covid, and have been down for a while.  Obviously I haven't had much opportunity for getting on the boat during this time.  But to answer some of the questions:
1. Yes, I've added a folding swim platform, however I had the same problem with exhaust fumes before I added that, and adding the platform doesn't seem to have made any difference, good or bad. When it is folded up, it only sticks out about 2 inches, and I keep it folded unless we are deboarding into the dinghy.
2. I mostly experience the problem motoring into the wind.  I've attached a diagram I stole from the internet that shows what I believe is happening.  It is a common phenomena in speed boats.
3. I hadn't considered the effect the pushpit-mounted seats might have before now.  I'll have to experiment and see if removing them helps.
4. Weather cloths on the pushpit might be an easy thing to try.
We are getting close to haul-out time, so I don't know if I'm going to have much more opportunity to experiment this fall. Thanks to all for your input and wisdom.