Thermostats necessary? and stripped inside threads, help!

[darkhorse]

Hey yal, been a while, Happy Fathers Day.

I have a 2003 Mercury 200 XL Saltwater. I replaced my waterpump/impeller, and decided to check the thermostats. I found a corroded mess of rubber seals and the old thermostats just about missing.
So I bought 2 new therms and gaskets and installed them. I waited for water to pump out of the pisser for about 1 scary uncomfortable minute and water was spiting out running down side of motor, No stream.

So I then took out the thermostats, tried again and water was coming out of the pisser a nice steady stream.

SO what gives? Do I need thermostats? or can I run without them.



And another problem. I stripped the thread on one of the inside bolts of the thermostat plate. HELP! Do I need to buy a new plate?$ or have it retreaded (is it something I can do myself?) so water does shoot out and the seal it tight.

[Juan]

Thermostats open fully when they reach a certain temperature...if they're new thermostats, maybe you didn't let it run long enough for them to fully open. You could take them out but I wouldn't recommend it... Your motor could still overheat after removing the thermostats even if it's peeing better. The thermostats keep your motor at the right operating temperature, they slow down the flow of cooling water from the water pump so heat transfer can take place. They apply a restriction in the passage of cooling water through the engine block. The restriction slows down the flow and allows heat from the engine to be transferred to the cooling water. Removing the thermostats removes the restriction, and without the restriction water flows so quickly through the block that little or no heat transfer takes place and you get overheating problems.

If I wanted to attempt to repair the stripped threads, I'd try to rethread the hole with a tap and dye set and use a different threaded bolt in that hole.

[darkhorse]

Capt. Juan

Rethreaded the hole with the helicoil tap and dye set. Success. Thermostats finally opened with some revving of thew throttle. Water is pumping out weaker than I am used to but pumping out none the less.
The water that is coming out is Fin' HOT, cant leave hand there too long. How hot should it be from running only 5 minutes? Please advise.

Also therm seals are leaking a little through the cracks so I need to put some silicon sealant in there.

Safe Link to my running the motor.

Thanks

[Juan]

darkhorse, First: from the video it looks like you don't have enough water pressure coming from the pee hole... Are you getting an over heating alarm?
Second: The water coming from the pee hole should be pretty hot... I don't know what temperature thermostats you have, but they are designed to open when they reach a certain temperature (probably around 120 - 140 degrees) so when they do open, the water will be close to that temperature and then will rise a little as the motor dissipates heat.

Based on your video (and posting that video was a great idea), and the reduced pressure at the pee hole, I'd guess you either need to change your water pump impeller or there is a restriction in the cooling system somewhere... try running a piece of steel leader wire up inside the pee hole as far as possible to be sure there's no blockage there..

You could have sand or debris inside the block if the motor has been recently run in sand or mud.

I'd put the boat in the water and run it to see if it pees stronger and gets cooler when you open it up... My best guess based on the pee stream is you may need to change the impeller.

[T-Topless]

I haven't had thermostats in 5 years on my Yamaha ProV200 .. but I don't run in water cooler than about 50 degrees in the winter and 81 right now. Prop best to have the thermostats.

On my Yamaha, there is a bypass valve that sticks and causes overheating at idle (trolling). It is easily cleaned and fixes this annoying problem. Not sure if Merc has a similar (hopefully better) setup.

[darkhorse]

Thanks T-topless and Captain Juan

I replaced the waterpump with a brand new one and impeller. I took her out on the water today and ran her HARD and didnt have any alarm issue. Water pressure running may be a little better but it still trinkles and is semi hot. The head is fairly hot to the touch as well. I think the parts guy gave me the wrong thermostats because I checked the peehole for debri. Thats my only guess, or maybe thats just how its suposed to be because I have never had therms. Going to get a temperature gauge installed soon and try it again. Ill keep ya updated

Gracias amigos from down here in Miami.

[Juan]

Hey, I'm from Coral Gables.... You might be right about the thermostats being the wrong ones. While running, you should be able to hold your hand on the head...it should be very warm, but not hot and there should be a good stream of water from the pee hole... There's gotta be a partial blockage somewhere imo.

[Simple Man]

Jun 16, 2013 13:27:50 GMT -6 Juan said:

....Your motor could still overheat after removing the thermostats even if it's peeing better. The thermostats keep your motor at the right operating temperature, they slow down the flow of cooling water from the water pump so heat transfer can take place. They apply a restriction in the passage of cooling water through the engine block. The restriction slows down the flow and allows heat from the engine to be transferred to the cooling water. Removing the thermostats removes the restriction, and without the restriction water flows so quickly through the block that little or no heat transfer takes place and you get overheating problems....

I've been thinking about this. For an automobile this is absolutely correct but I was thinking it was because water flow through the radiator was too fast to transfer heat out of the system and not transfer of heat from motor to water. In an outboards case, the radiator is obviously a non issue. If he is in Miami, cold water is a non issue too.
I'm thinking the motor might not get warm enough without therms and that would possibly effect gas mileage. Am I missing something on the heat transfer issue?

That being said, I think you need to find the issue and repair so that you can keep the thermostats installed. Mercury has what they term a poppet valve on most of their engines. It's like the bypass valve on a Yamaha that T-topless mentioned. It will cause problems like you are experiencing. If your motor has one (and I think it does) replace it before messing with the thermostats more and see how it runs.

[CaptWoody]

I'm inclined to agree with Juan, there should be a good stream. But I recently owned a Force engine that was made by Mercury and it has a very weak stream while running on the muffs and only a so-so stream in the water, but it did keep the engine cool. I never had it overheat.

[darkhorse]

Hmm all of this sounds like we narrowed it down, i will look into changing poppet valve and reconfirm I have the right therms.

[T-Topless]

Yes, the bypass on my Yamaha was sticking. Just took it out and cleaned it. Didn't seem like I did much, but it never overheats at long idles anymore, so now I can troll for Spanish again!