Aftermarket thermostat

[1ranger487vs]

Anyone have experience with the aftermarket thermostats out there. I would prefer oem but the price of mercury parts is forcing me to look elsewhere. I just don’t understand why a mercury thermostat are so expensive. I can get one for my truck for under ten dollars, it’s basically the same design. Please enlighten me. Love my engine but I’m scared one day a compressor or lower should fail a good engine would not be worth fixing. Am I alone. Appreciate all your help

250 pro xs. 2b116638

[Bob G.]

I’d stick with Mercury OEM. My take is that if I can have a bass boat and pay for registration, insurance, gas and oil, I can afford Mercury parts. I’m trying to keep my boat until I’m no longer fishing.

[JOE54]

ive tried um all no luck with any other than OEM ,,,,, good luck now JOE

[Bryanmc57]

I always think about a Bell helmet ad I saw back in the early 80's.... "Got a 10 dollar head, buy a 10 dollar helmet." Those oem thermostats will seem cheap if you lose a powerhead because an aftermarket one fails.

[fly by night]

So true!

I always think about a Bell helmet ad I saw back in the early 80's.... "Got a 10 dollar head, buy a 10 dollar helmet." Those oem thermostats will seem cheap if you lose a powerhead because an aftermarket one fails.

[1ranger487vs]

But why are mercury parts so expensive. It’s a thermostat. Like a lot about my opti but when you look at the prices for injectors, compressor or a lower unit it’s outrageous. In all the years, I never had a problem with thermostats. Just asking for real world experience. I never believed oem is the only way to go. Some things yes. I asked similar questions before on oil. Got plenty of feedback and been running pennzoil for many years not dfi. If you have tried an aftermarket thermostat please let me know what you found out.I don’t need all the only oem for me responds

[JOE54]

maybe a supply demand game , i was advised there will b e no more dressed powerheads built at MERCURY MARINE for optimax engines

[1ranger487vs]

Thanks joe I appreciate your advice

[EuropeanAM]

But why are mercury parts so expensive. It’s a thermostat. Like a lot about my opti but when you look at the prices for injectors, compressor or a lower unit it’s outrageous. In all the years, I never had a problem with thermostats. Just asking for real world experience. I never believed oem is the only way to go. Some things yes. I asked similar questions before on oil. Got plenty of feedback and been running pennzoil for many years not dfi. If you have tried an aftermarket thermostat please let me know what you found out.I don’t need all the only oem for me responds

Don't waste your money on aftermarket ones. They are junk with four capital letters.

Not only do they not come up to temp... some of them actually rattle in your hands because they're built with sloppy tolerances and held together with circlips.

You're right... the parts are becoming more and more expensive, and that's not likely to get better. When those engines were in production- they could order 100K thermostats at a time. Now they're only having them made for replacement/maintenance purposes, costs a lot more per part when the order volume drops 90+%.

[bass.man65]

I have used a lot of WSM stats and they are just as good as anything Mercury puts out. As a matter of fact if I gave you one of each you could not tell them apart. Just never buy any from China.

[1ranger487vs]

Thanks I really appreciate all of you

[Proline25]

I was testing my Mercury thermostats yesterday. One started to open around 110 but didn't fully close after letting it cool, one opened at about 135. I found the spare Mercury thermostat in the toolbox and I placed all three in the pot with a gauge. two opened about the same time so I didn't put the one that opened early back in the motor. While testing the thermostats over and over I started to just buy two new ones until I saw the Mercury stats were about $100 each. The WSM was about half that price but it's hard to trust an aftermarket part. Had I seen this post yesterday it's likely that I would have ordered the WSM stats.

[jdskeeter]

I just recently learned my lesson on cheap thermostats. I was having a sporadic overheat issue that was eventually remedied by replacing the thermostats. I put in a set of cheap ones that fixed it. After about 6 months, the same issue occurred again. I’ve since replaced them with mercury thermostats, the original ones lasted over 600 hours and were removed and cleaned numerous times before failing. For something so critical to engine life, I wouldn’t take the chance based on my own experience.

[jerzia]

Don't know about any of that, but I went through 4 OEM Merc thermostats last year before finding two that opened and closed relatively at the same time. One brand new one wouldn't open until well over 140 degrees, and another took forever to close.

[EuropeanAM]

I have used a lot of WSM stats and they are just as good as anything Mercury puts out. As a matter of fact if I gave you one of each you could not tell them apart. Just never buy any from China.

Sorry but- got to call that one what it is. No offense meant to you, but here's MY experience:

I've ordered direct from WSM, and they're probably the WORST of any of the aftermarkets I tested/checked.

ZERO of 4 thermostats came up to 120 degrees. Most of them sat in the 108-113 range with 65F water temp. Still have them in my box where I removed them (same day powerhead test ran) and replaced with the OEM thermostats.

They "look" like they might be good based on the copper/brass components, BUT the seat and spring arms are considerably thinner than the OEM, and the valve appears to just be a stamped metal disc.

The thermister isn't even securely affixed to the thermostat body (physically loose) This affects the point at which the valve actually begins to open.

DON'T use them unless you've got a spare powerhead ready.

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