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Check Valve 21-8781051

Satisfaction rating 5 out of 5 (20 Ratings)
$31.95
You save $2.13. (6%) $34.08
ONLY 2 REMAINING
Ships Immediately
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Product Description

Mercury factory part. Search for more factory parts & parts diagrams.

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20 Product Reviews

Mercury Optimax 150

Repair Difficulty
Medium
Repair Time
1 to 2 hours
Crowley has what you need to maintain outboards
by

Problem fixed: Oil tank would not fill

Check valve was bad

200 hp mercury

Repair Difficulty
Easy
Repair Time
30 to 60 mins
They got me a part that I hard time finding
by

Problem fixed: Lot of smoke start up

Replaced oil air pressure check valve

Mercury 135hp Black Max

Very easy to work with and great communication with order status and tracking.
by

Mercury Outboard 175 V6

Repair Difficulty
Medium
Repair Time
More than 4 hours
Online store easy to use, find OEM parts. Good service
by

Problem fixed: Excessive smoke.

Compression is good 120 all around. Replaced old check valves for fuel/oil lines. Didn’t fix problem. I’m now going to look for air leaks in fuel lines which can cause excessive smoke.

150 Mercury

Repair Difficulty
Easy
Repair Time
Less than 30 mins
I’ve purchased numerous times with Crowley marine. I’ve always gotten the correct part for my engines. Shipping has always been fast. I’ve never had to work with the customer service as everything has always been timely and great.
by

Problem fixed: No oil pressure in reserve tank

Replaced the check valve on the engine leading to the remote oil tank. Problem solved

by

Great
by

It took over a month to get my parts not sure if covid 19 had anything to do with it or not but parts was right on
by

200 mercury

by

by

by

They got me what I needed quickly and at a competitive price. I highly recommend.
by

I have purchased many parts for my 150 Mercury and my 30hp Yamaha. Parts Break downs are good and I get the right part every time.
by

Perfect transaction, Swift shipping
by

Everything was good.
by

1985 Mercury Black Max 150 hp Long Shaft

Repair Difficulty
Easy
Repair Time
30 to 60 mins
Good. However as a Canadian buyer I would have preferred to ship via a more expedited method. The projected ship to times would be helpful as I'm approaching two weeks for my last order and only now see it entered Canada though FedEx tracking.
by

Problem fixed: On-going low oil alarm periodically going off.

Have been working to solve this on-going low oil alarm issue and have slowly (hoping) to finally be resolving the issue here's how; 1) replaced the control module due to water getting into it causing a 'false' alarm. Bought a 'used' one on ebay for $85. Works great. Temporary alarm fix. 2) bought a new on-motor sensor cap for the remote oil tank due to a crack on the cap causing loss of pressure and the oil level dropping setting off the alarm. Temporary alarm fix. 3) Replaced the two oil feed lines to the main tank; both had cracks at the fitting at the tank. Replaced the hoses. Temporary alarm fix. 4) checked the 2 p.s.i. check valve which the 'pressure' hose is connected to at the crankcase; I could blow air in both directions, which I shouldn't; loosing pressure in the remote reservoir at low speed. Oil is unable to be fed up to the engine reservoir with steady pressure due to the leaky check valve....I think. Ordered the new valve from Crowley and will report back if this finally solves the on-going issue. 5) if this doesn't solve it I will disconnect the whole system and run pre-mix 50:50.

mercury 225

Repair Difficulty
Hard
Repair Time
2 to 4 hours
by

Problem fixed: oil tank not being filled when engine is running

we requested the part via normal post and never received it. When we contacted Crowley they reimbursed our previous purchase and resend it via priority post. great service!

Mercury XR6

Repair Difficulty
Easy
Repair Time
Less than 30 mins
Great!
by

Problem fixed: Loss of oil to cowl resevoir

Noticed my boat was pulling off the cowl tank rather than the reserve tank. Replaced the 1 way check valve after I blew through it both ways. Fixed the problem quick and easy!

by

Mercury 240 Jet

Repair Difficulty
Easy
Repair Time
Less than 30 mins
Easy to find the right parts, quick shipment.
by

Problem fixed: Oil not flowing from reservoir to engine mounted tank

Crankcase check valve not working. Replaced check valve and it is working now.

Product Fitment Grid

This guide is to be used as a reference only. You must verify fitment using your model or serial number.

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Supersession Chain

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Crankcase CHECK VALVE 432783 878105
DRAIN FITTING 432781 432783
CHECK VALVE FITTING (CRANKCASE) 43278 432781
Due to manufacturer policy OEM Mercury products can only be shipped to addresses within the United States.