www.iFourWinns.com

I have owned my boat for 4 seasons and have posted before about issues with one of my engines periodically losing power. Numerous mechanics have tried to diagnose and have looked at and fixed or ruled out fuel filters, anti-siphon, electronic throttle issues, etc etc

Nothing every explained it. I finally found one guy who was insistent on continuing to search for the issue and during an extended sea trial he concluded that due to a combination of poor design and possibly a small exhaust leak somewhere, CO is building up in the engine compartment and starving the engine of oxygen temporarily which shuts it down.

He noted that on the 358 Vista there are just 2 relatively small air intake holes on each side. We compared to several other models of similar boats in the marina and sure enough, every other model has MUCH larger opening for air intake and often scoops to assist intake.

In addition, on the port side the 2 holes have tubes attached to them and on the starboard side they are just open holes in the fiberglass. The way the tube angle back seems like it would seriously inhibit air flow in to the engine compartment and the fact that it is different on each side might explain why only my port engine was affected but starboard was not. (air flow uneven in compartment)

I am wondering if anyone else has ever dealt with this or noticed anything similar. It is a difficult problem to nail down because air flow can be so dependent on humidity, temperature, wind direction, travelling direction, etc.
It is hard to tell if running with the blower on helps. It certainly doesn't cure the problem.

Suggestions to fix include adding some aftermarket fan/blower and cutting additional holes in the fiberglass. There is room to cut some openings that would still be hidden under the cowling.

Thoughts?

Have you tried running it with the engine hatches propped open a few inches? If this cures it, I would say he nailed the problem.

I would think if one engine is totally snuffed out by this theory, the other would surely lack major power as well. Just my opinion, but I think he's barking up the wrong tree.

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07 Azure AZ200,
Previous boat,
95 278 Vista,
And a lot of others.

Ontario, Canada

How often does it cut out?

And, I agree with the above. Run with the hatch opened up a crack and see what happens.

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2004 - 288 Vista
Twin - 5.0 Volvo Penta GXi DP

Was the flame arrestor taken off and cleaned out in solvent? Did they check for other problems such as vacuum leaks?. It would be odd if this issue (lack of air) would not affect both engines unless there is some yet undiscovered factor affecting this engine.
As noted you could try running it with the hatch open a bit or even temporarily fab up a vent hose using blower hose to that engine and see if it helps. Gas inboards must have a blower but the venting is important. There should be a hose on the side with blower the goes from the bilge up to the blower housing. Then you have another hose going from the blower housing to the vent on the gunnel. Ideally you should have a directional vent that faces aft on that side; this helps pull vapors up and out of the bilge. On the other side there should be a hose extending from the vent down to the bilge, with a directional vent facing forward. This helps force fresh air into the bilge. On my boat the vents were non directional and there was no hose on the side without the blower. So I installed directional vents and a fresh air intake hose on that side.

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88 Four Winns 200 Horizon
4.3 OMC Cobra-4bbl
2002 Walker Bay 10/2012 Suzuki 2.5
2008 Walker Bay 8

1998 Jeep Grand Cherokee 4.0/Selectrac
2007 Jeep Grand Cherokee 5.7 Hemi/Quadradrive II

Yes, of course, running with and without the hatch open is how we discovered the issue.

The question is more if anyone else has seen this and if anyone has thoughts on fixing the air flow issue.

Generally only the port engine loses power and that obviously causes my to throttle back so the starboard may be about to go too but then I pull back.
Occasionally both cut out at the same time.

install bigger blowers and bigger air pipes feeding the blowers.
I always leave blowers on when engines running.

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GI Auz
2004 288 Vista
Twin 4.3 Merc


Previously:
Beneteau 411 Non-Stink

I realize I'm late to the party here, but I upgraded the power in my 238 Vista (from 5.8 270hp to 5.7 320hp) and also added two conventional looking louvers in the gunwale sides and ducting to completely change the airflow pattern in the engine bay. The air intake and exhaust was all in the rear on my model and sucking engine exhaust in while running. I added two forward facing louvers with collectors for intake air and left the rear vents (under the rear bench by the way) for exhaust only, i.e. bilge blower. Seems to work well. Your specific application will require different placement of additional vents obviously. Long story short, add more ventilation to the engine compartment but do it in a way to avoid water intrusion either rain or sea induced.

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'96 238 Vista Dlx w/ 2001 Volvo 5.7 GXI and Duo Prop outdrive

You should not need to run your blowers when your under way. The engine compartment should naturally vent it self with the air scoops. Which goes back to the small vent holes.

Here's some pics of what I did for our boat, obviously your situation will be somewhat different.
[img][/img]

[img][IMG]http://i1305.photobucket.com/albums/s544/Jon_Pangborn/bfde8b71-4a69-45c3-b2a0-05e46604fbf7_zps7mkvgjrh.jpg[/img][/img]

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'96 238 Vista Dlx w/ 2001 Volvo 5.7 GXI and Duo Prop outdrive