4 Stroke Outboards: Cold Weather

[KYSkipper]

My old Carbed Evinrude on my old Ranger has a big difference in power in cold weather v's summer time. I sometimes change props from winter to summer to accommodate it.

My dad has an EFI Merc on his and I've never noticed much difference in power between cold weather and hot weather. I assumed my SHO would be pretty much that was. I'm now thinking not so. I've notice the power on the SHO has increased a lot in cold weather. Just wondered if that was normal?

[born 2 fish]

Yea that's normal better air it's more dense.

[basscla]

I haven't noticed a difference on the Merc 150 4s or 300 Verado.

[Nova Kaw 650]

Cold air is denser and therefore makes more power, IF the engine can sense the cooler/denser air and compensate by adding more fuel.
Your carbed motor could not adjust itself, but the SHO most likely can.

[billnorman1]

Cold air is denser and therefore makes more power, IF the engine can sense the cooler/denser air and compensate by adding more fuel.
Your carbed motor could not adjust itself, but the SHO most likely can.

SHO 'nuff should.

[Nova Kaw 650]

SHO 'nuff should.

LOL

[Matt1212]

Cold water is more dense, gonna be faster

[KYSkipper]

Cold air is denser and therefore makes more power, IF the engine can sense the cooler/denser air and compensate by adding more fuel.
Your carbed motor could not adjust itself, but the SHO most likely can.

Carbed engine lost power in the heat of the summer. I ran a 24 inch prop in the winter and 22 inch July and August. I know about the cooler denser air. I just knew it didn't make much difference with Dad's EFI and figured the SHO would somehow compensate for it.

[DeGraaf]

A carbed motor will run faster and better in colder temps because as said, the air is more dense. The air to fuel mixture is leaned out and performance gains are there.
There is a built in margin of over fueling in the jetting for cold weather. Ski-Doo had carbs that adjusted float bowl pressures to compensate for temp and bar. press.
It was called DPM and worked great on snowmobiles, which run from 40 degrees some days to below 0 others. If you have an old carbed Merc or Rude they run awesome
on cold days especially under 1500' to sea level. Over fueled 2 stoke=smoke, sputter and long engine life. Too lean=BOOM & $
Direct inj. 2 strokes are a huge leap forward in performance and economy.

[Fishysam]

I haven't noticed a difference on the Merc 150 4s or 300 Verado.

The 150 will have less ability to make more power so it's harder to notice, the supercharger probably negates the naturally aspirated boost of more air since it has computer controlled boost

[grout-scout]

Just chiming in, I was shocked to see my 2 stroke Pro XS run 400 more rpms on a colder morning. Sure is a big gain, my old yami OX66 didn’t vary that much.

[gehol]

Cold water is more dense, gonna be faster

LOL

[JR19]

LOL

Laugh if you want be there is a very small difference. A prop will get better bite in dense water, thus being more efficient in 40* water verses 85* water. The difference it makes is minimal but it does happen. Plus as previously mentioned boat motors have the tendency to make a little more horsepower in cooler weather. Again this is also very minimal. When you add the two gains together people have seen 1-3 mph increase with motors that have 150-250 horsepower. I know my motor picks up 100-150 rpm in the cold months and that gains me about 1 more mph. There is a few people that actually have enough difference between cold/hot they run a "winter" prop and a "summer" prop.

It's been said many times in the past that if someone is dialing in their rig for performance and it's in the summer heat get it set to be within 200 rpm of max operation because come cold weather it will be right on max operation. It's just the opposite for winter. Set it right on max rpm because come summer heat you will lose 1-200 rpm. This has to do with the combination of water density and engine performance in the cold versus heat.

[JoshKeller]

my jet gains 3-400 rpm in colder air vs summer.

[Buccaneer]

I move from a 25 Tempest+ summer prop to a 25 Croxton Razor in the winter, air temps 50 or less water same temp range and can hit 6K RPMs on a 150 Etec G2 HO. Summer on the Razor 5600 RPMs, Tempest+ 5900-6K.

[TobyG.Mo]

Same here on the prop, keep a summer and winter prop.

[Nova Kaw 650]

Laugh if you want be there is a very small difference. A prop will get better bite in dense water, thus being more efficient in 40* water verses 85* water. The difference it makes is minimal but it does happen. Plus as previously mentioned boat motors have the tendency to make a little more horsepower in cooler weather. Again this is also very minimal. When you add the two gains together people have seen 1-3 mph increase with motors that have 150-250 horsepower. I know my motor picks up 100-150 rpm in the cold months and that gains me about 1 more mph. There is a few people that actually have enough difference between cold/hot they run a "winter" prop and a "summer" prop.

It's been said many times in the past that if someone is dialing in their rig for performance and it's in the summer heat get it set to be within 200 rpm of max operation because come cold weather it will be right on max operation. It's just the opposite for winter. Set it right on max rpm because come summer heat you will lose 1-200 rpm. This has to do with the combination of water density and engine performance in the cold versus heat.

It's not the water temperature causing the change; it's the air temperature.

[n2ratfishin]

My best speeds to date even with my little 115 4 stroke have come during the winter. I've yet to have a boat that wasn't that way.