how to stay warm in a wetsuit?

As I mentioned in a different thread, I sent my drysuit in to Kokatat for a leak test, and they say the fabric is delaminating. Fortunately, they'll replace it under warranty. Unfortunately, the estimated shipping date for my new drysuit is in July.

So, unless I win the lottery, I'll be wearing my old NRS farmer john wetsuit for the duration. I wore it on Thursday in Santa Cruz, and in spite of it being an unusually warm day, I froze my heiny off. It was white-capping, and on my AI, I was constantly getting splashed with water, not to mention sitting in a pool of ice water. That's pretty much par for the course on the AI, and it's no big deal with a drysuit. But the wetsuit was not doing the trick.

I can rig a seat that'll keep my but out of the pool of water, but there is still the constant splashing. What's the key to staying reasonably warm in a wetsuit under such conditions?

First, keep the core warm so it can pump warm blood to the extremities.  I start with a long sleeve base layer under my farmer john.  200 weight merino or lightweight synthetic on warmer days, go up from there -- merino as your base layer reduces stink.  If it's below 50° F air temp, I add a synthetic layer over the top, too -- a fleece pullover on really cold days and mid-layer for borderline days.  Those comprise the warming layers.  Now, to prevent evaporative cooling from splashes,  you need to stay dry.  A paddlejacket over the top and splash pants over the bottoms do that for me.  I wear simple rain overpants on the bottoms if it's going to be a particularly sporty day.  I wear my paddlejacket most days as a wind breaker in addition to splash protection.  The pants and jacket aren't intended to keep you dry in the water, just protection from splashing and evaporative cooling when atop the kayak.  If you wind up going for a swim, the pants and jacket hold no water, so they don't affect your ability to self rescue.

I wear a 2mm jacket over my 3mm farmer john. Usually does the trick. I also wear a paddling jacket over that when its colder. I wear 2.5mm socks and 2mm booties. Im always comfortable and when I get too hot I can always take them off. The jacket a Oneill. Ive had it for a few years and its held up nice

First, keep the core warm so it can pump warm blood to the extremities.  I start with a long sleeve base layer under my farmer john.  200 weight merino or lightweight synthetic on warmer days, go up from there -- merino as your base layer reduces stink.  If it's below 50° F air temp, I add a synthetic layer over the top, too -- a fleece pullover on really cold days and mid-layer for borderline days.  Those comprise the warming layers.  Now, to prevent evaporative cooling from splashes,  you need to stay dry.  A paddlejacket over the top and splash pants over the bottoms do that for me.  I wear simple rain overpants on the bottoms if it's going to be a particularly sporty day.  I wear my paddlejacket most days as a wind breaker in addition to splash protection.  The pants and jacket aren't intended to keep you dry in the water, just protection from splashing and evaporative cooling when atop the kayak.  If you wind up going for a swim, the pants and jacket hold no water, so they don't affect your ability to self rescue.

Thanks! Great info--exactly what I was looking for!

   I do what the others have said layers on torso, plus splash jacket/pants,  but I also wear two pairs of long johns so my legs stay warm, though I have a kayak, so I'm paddling and not pedaling. 
   I use a pair of thin liner socks to tuck the ankles of the first long john into, then pull on the second layer, then pull the socks over both layers to be able to get the wetsuit legs up without pulling the under layers up.  And then  thick neoprene socks and dive booties.  And carry a surfing bonnet in case it gets really cold.  It's a lot of crap to have to clean up (throw everything in front-loading washer on cold gentle cycle and hang to dry) but I stay warm.  Bicarb of Soda paste for the pits of the fleece tops before washing cuts the odor.

   I do what the others have said layers on torso, plus splash jacket/pants,  but I also wear two pairs of long johns so my legs stay warm, though I have a kayak, so I'm paddling and not pedaling. 
   I use a pair of thin liner socks to tuck the ankles of the first long john into, then pull on the second layer, then pull the socks over both layers to be able to get the wetsuit legs up without pulling the under layers up.  And then  thick neoprene socks and dive booties.  And carry a surfing bonnet in case it gets really cold.  It's a lot of crap to have to clean up (throw everything in front-loading washer on cold gentle cycle and hang to dry) but I stay warm.  Bicarb of Soda paste for the pits of the fleece tops before washing cuts the odor.

Just to make sure... Remember not to wear cotton (thinking about the long johns mention). Cotton kills.

I wear a long sleeve light weight shirt under my wetsuit. Then I wear synthetic hiking pants and long sleeve shirt on top the wetsuit. Then I wear a rain suit on top of that plus hat with ear protection. I wear a knit hat that covers my face and gloves when it’s cold. I also wear two heavyweight socks and neoprene boots. I can’t bend over, but I don’t get cold. 

... though I have a kayak, so I'm paddling and not pedaling. 

Kayak*’s rule!

First, keep the core warm so it can pump warm blood to the extremities.  I start with a long sleeve base layer under my farmer john.  200 weight merino or lightweight synthetic on warmer days, go up from there -- merino as your base layer reduces stink.  If it's below 50° F air temp, I add a synthetic layer over the top, too -- a fleece pullover on really cold days and mid-layer for borderline days.  Those comprise the warming layers.  Now, to prevent evaporative cooling from splashes,  you need to stay dry.  A paddlejacket over the top and splash pants over the bottoms do that for me.  I wear simple rain overpants on the bottoms if it's going to be a particularly sporty day.  I wear my paddlejacket most days as a wind breaker in addition to splash protection.  The pants and jacket aren't intended to keep you dry in the water, just protection from splashing and evaporative cooling when atop the kayak.  If you wind up going for a swim, the pants and jacket hold no water, so they don't affect your ability to self rescue.

I’ve been rocking the splash jacket for a while, but just recently got myself a pair of NRS Endurance pants after a particularly windy and choppy/splashy day on the bay last month—they have been an absolute game-changer for me. You might be a little swampy in there but you definitely stay warm. When I get fish blood all over the place I can take my bilge pump and literally hose everything off, including myself, on the water without getting cold or wet underneath. Added benefit is the ability to remove them easily if the sun comes out and it gets warm. Couldn’t be happier with them. Would recommend.

Tedski:I should have said "synthetic" long johns, in case a newbie was reading.  Mine are recycled ski clothes - I now wear Smart Wool and synthetic fleece longies for skiing, which would be real toasty (and safe) for yakking, but the thought of fish smell on my ski stuff is more than I can stomach.

I wear Army issued poly pro long underwear bottoms, wool blend hiking socks, and my NRS mukluks.  A Kokatat paddling jacket or a fleece jacket depending on the weather.  Army Watch cap for the head of my ears are cold.