You are using cast iron exhaust manifolds? I have heard alot of problems with the alum. GLM manifolds. If you are using cast iron, I have never heard of this happening with the way you winterize them.Mystery?????

Yeah mystery! And it SUCKS! Yes the manifolds are cast iron from Mercruiser. So does anyone see anything that I am doing wrong??? Please reply, this is getting expensive. I did try the "running the anti-freeze through the engine block thing", but I didn't remove the t-stat. No one told me to either. But that was when I first bought the boat. After that, I went strictly by the book. Any danger in just running the boat like this? I'm sick of dropping $2 K everytime these things crack!

You say you remove the plugs from the risers and fill them with anti-freeze, are you draining the manifolds at the bottom. Cooling water enters the manifold at the bottom and comes up through the risers out the boat. There should be a drain plug on the bottom where the hose connects or just remove the one inch water hose to drain the manifold.

BajaHammer98, bimini run...I take it you are the same person?

Do not run the motor with a cracked manifold, even once. If you do, you could be spending more than the $2000 to repair.

When are you finding the cracks, at 1st spring start up, middle summer or in the fall?
Both manifilds each time?

It has to be in your winterizing methods. You aren't diluting the RV antifreeze with water? Use it full strenght. If you simply remove all the hoses and drains from both the motor and manifilds and drain out the water (including the supply hose to teh seawater pump and the coolers) and pour in the AF, you should be fine. Actually this is safest. I take it this is how you do it if I read it right.

If you are running it on the muff, how long are you running the motor on straight water before pouring in the AF? Motor temp? And how are you pouring in the AF to the muffs? You can't just pour in the AF after running the motor on the hose till it comes out purple then stop. Gotta run it extra to make sure no dilution. This way does make for waste of AF though.
Being in NY, you have to be more protected.

When it was covered the 1st time under warrenty, there was no question about it not being winterized correctly? Was it covered the 2nd time also? I'd be surprised if Merc would replace manifolds for inadequate winterization. Maybe they see something else?

US1 Fountain, BajaHammer98 is my son and we are both trying to resolve this issue. And, what u said is exactly how i winterize my boat. Remove plugs and all hoses, and fill the block using straight AF. NO water added. Wondering if, because it's impossible to get all the water out of the block, could that be diluting strength of the AF?? Is there a way to completely drain the block? Use a compressor with an air nozzle? Because i just let gravity do it's thang. Also, the first time it happened, I think I caught it in time. I ran a space heater for a week and defrosted the block. Didn't notice any problems until a couple of years later (loss of power; 2 or 3 dead cylinders). Then, my marina somehow repaired it under extended warranty. The 2nd time was on me. And now I am pretty sure it's happened again (same symptoms). I haven't brought it in to get diagnosed as I will be charged for that and I am ready to take the boat out into the ocean, sink it, and collect insurance. :drink:

If you don't remove the T-stats the chances are you're not winterizing your entire cooling system. If the T-stats stay closed it won't allow the anti-freeze to run through the blocks. You could simply heat up the boat until they open and then put the antifreeze in, but I always worry about them closing and me not knowing about it. I find that it is much easier to pull them for the winter (and I leave the housings off, just in case)...


You might want to pay a professional to winterize your boat next year, and stick around to see what they do differently. Do you keep your boat at your house for the winter?

[QUOTE=wjb21ndtown;3035936]If you don't remove the T-stats the chances are you're not winterizing your entire cooling system. If the T-stats stay closed it won't allow the anti-freeze to run through the blocks. You could simply heat up the boat until they open and then put the antifreeze in, but I always worry about them closing and me not knowing about it. I find that it is much easier to pull them for the winter (and I leave the housings off, just in case)...

wjb, I have never ran the motor long enough to open t-stat, and have winterized 1000's + with no problems. Mercruiser says the t-stat will close back up because your A.F. will cool it down, Unless you have some kind of quick change over valves for your A.F.? I would always run a motor to winterize!!!!!!!!!!PERIOD!! Unless it is a alpha unit can run back through the drive. We do winterize boats that are left in the water, And we remove the hose from the seapump and run at least 5 Gal. A.F. through it, And have never had a problem with them, And the water does freeze here.

Thanks for the input SR...

I guess I'm just anal about winterizing my stuff. I drain as much as I can, and I leave open as much as I can (I leave the drains on the mainfolds off all winter. I figure the more antifreeze in the motors the better, the less stuff you have restricting any possible freezing the better, and if there isn't any fluid at all in whatever location, then there's nothing to freeze....

Manifolds are not that big a deal to remove, I have to remove mine just to make it easy to change spark plugs and I have a close set twin engine boat. Take the two of them off and put them on the living room coffee table for the winter. Then winterize the block as you normally do. I ran aluminum Stainless Marine manifolds on a Small Block for 7 years in Upstate NY, never a problem with freezing, always did it myself.

WJ, I don't need to remove the T-stat because I don't run the engine to winterize. It's all done by removing all the plugs within the block and all heater hoses and hoses feeding the risers. I then remove the T-stat housing and pour AF into the block and all hoses until full or AF runs out the exhaust. That's normally about 5 gallons, give or take. And BTW, the manual for that engine indicates that's about how much liquid the block will hold.