Hot Day vs crappy running motor

"We took the boat out for the

"We took the boat out for the weekend and on Saturday it was hot! According to my keychain thermometer it was 95 degrees and it felt every bit of that. I noticed my boat doing some funny things. It wouldn't idle worth a damn going into the docks, very rough and dying. Then hard starting, slow starter and long turn over time. It was doing this mostly in the afternoon and evening. When running it was running smooth and the temps and oil pressure were normal for this boat. It just wasn;t idling or restarting for crap. Well lo and behold, Sunday we got up and loaded up the boat to go have breakfast in another harbor, hoping the boat would make it. Now it's 25 degrees cooler on Sunday than saturday and the boat runs flawless again. Starts right up, idles fine coming into the docks, no problems at all all day long. Anybody else ever experience this on a hot day? Is my fuel/air mixture off a bit? Maybe a mild form of vaporlock? Anyhow, weird."

"PS:

Intense heat can do so

"PS:

Intense heat can do some strange things as you have witnessed. I don't know what your air ducting is in the engine bay, but, the more air available the cooler the bay. You can insulate the fuel lines to reduce heat gain from the engine.

I have two 3" outside air inlet ducts, one to the bilge and one to the front of the carb; both inlets are forced air while underway. I changed the bilge air exhaust duct and fan from 3" to 4". I also have two more 3" floor level passive air vents. The blower runs continuosly."

"Thanks Guy,
That's a go

"Thanks Guy,
That's a good idea. We don't have too many 90+ degree days here in Seattle but the extra venting can't hurt. My engine bay is always quite warm even on a cool day. I'm sure it was a whole lot warmer when it hit 95. I also found out I need a new battery. If it had any weakness it really showed up when it got hot. Hasta."

try the fuel cap vent we dont

try the fuel cap vent we dont get by freezing in scotland lol but have had the same problems when my engine was warm happy boating

"Almost certainly vapor lock.

"Almost certainly vapor lock.
Try this next time: Splash some cold water on the fuel lines, filters, and fuel pump.
If it straightens out, for sure it's vapor lock.

Who knows, you may have gotten a tank of off spec fuel and it may never do that stunt again?

Rod"

Battery will do it! even if yo

Battery will do it! even if you have two with out a switch to isolate them one bad battery will make booth act like one bad one!

"Hot temp + weak Battery =

"Hot temp + weak Battery = troubles? Good guess.

I just bought a new 750 MCA battery from Costco so we'll see. For $67 I think it will be more than worth it.

I would say our summer is coming to a close here in the Pacific Northwest so I don't expect anymore 90 degree days until next year. It's been like October this week! I hope we at least get an Indian Summer, I'm not ready to winterize just yet."