62T Low End Bog and Uneven Cooling

[HiImScott]

I have a RN Superjet with a 62T/62T 701 out of a WaveRaider. The ski has stock dual 38's with stock FA (2 of 3 screens have been removed), stock head, Factory B-pipe, and dual cooling. It has always had a low end bog/hesitation that I haven't been able to figure out. I have two main questions:

1. What carb jetting should I expect to have? Will it be different because of my 62T cylinders? I currently have my jetting at 70 pilots and 135 mains, but I just learned the WaveRaider stock jets are 67.5 pilots and 120/130 mains. Looking at my plugs they are not even in color, and they are both darker in color.
2. Next question is related to my dual cooling. In the past I ran the engine and pipe on two separate circuits entirely, and the ski still had the bog. In an attempt to go to a cooling method that I believe is more common I changed it to the picture below. By doing this a new problem came up... my pipe and water box are running way too hot. I found that the rear outlet on my head flows much less water at much lower pressure than my front outlet, and I don't believe it is plugged (I will double check this tonight). There isn't even enough pressure out of the rear fitting to open my FCV under throttle.

 

[IS0LD0UT]

That cooling diagram is how I run mine. You may need to restrict the pisser that t-s with the flow control. Water is going to flow to the least resistive path or take some washers out of your flow control.
The stock head with gasket has different sized holes, depending on where the second one is tapped you may be taking more flow? Maybe restrict that pisser too. I run about a 4mm opening most of the year.

 

[Roseand]

Same exact cooling setup I run. I have to use restrictors to get proper pressure to open the fcv. If I didn't use a restrictor my fcv would never get close to opening and I melted a cooling line and overheated/almost blew up my fiberglass waterbox learning that lol

 

[HiImScott]

Should have menitoned this, but I actually was running a 4mm restrictor in the cooling line out of the front head outlet. When the FCV didn't open I unhooked both the front and rear lines from the head and just let them dump into the hull temporarily with the ski tied to a tree, and the front one sprayed like a fire hydrant while the rear one just kind of pissed out a little bit of water. The problem is definitely somewhere between the exhaust manifold and head. Just figured this may be 62T cylinder/head related? I suppose I may have to pull the head tonight.

 

[IS0LD0UT]

Try that test again with a restrictor in the front. Think that is tapped in a place where its getting full flow meaning the rear is not getting much.

 

[Dartman]

make sure you check the headgasket
wrong ones will have the cooling holes where the casting bridges are and block the holes
possible you have std 61x gasket on the 62t head?

 

[HiImScott]

Checked my head gasket and it was very corroded, but none of the holes were plugged. Not sure how to tell the difference between the 61x and 62t head gasket. All the holes appeared to line up though. I have now checked all of the cooling paths, and they are all clear. Is doesn't look like the rear of the head has as many passages to begin with though. Maybe it is common for 62t heads to flow less water through the rear outlet?

 

[Dartman]

make sure you buy the 62t part # gasket
not starting with 61x part #
when you use the 61x gasket the holes are not in the same place as the 62t gasket
there are casting bridges in the 62t heads that the 61x head dont have
yamaha had to move the cooling holes in the gasket to miss the bridges in the 62t head
this is the reason for 2 different headgasket part #s