Mercury 5.0L TKS Carb. Question

[Nashville]

We have a 2009 Sea Ray 205 Sport w/ Mercury?s 5.0L TKS (Serial No. IA606447). The motor has about 125 hours as of today, 9-3-2012. All in all, this has been a pretty good boat and motor combination. However, have been researching the carb. for about 8 weeks now following yet another carb. rebuild to address the rough idle condition that develops each season. In general, most don?t seem to like the TKS carb. and my experience with it seems to follow many of the negative comments. While I don?t mind "pumping" the throttle to start the motor, and it readily starts when I do, I am growing tired of the frequent cleaning and rebuilds this Mercury carb. requires and the nagging performance issues. So, debating whether to install a 4 barrel Rochester or Holley. Wondering if anyone has experience with this and the results. Also wondering if either of the proposed carbs. bolt straight onto the Mercury intake or if an adaptor is required. If an adaptor is required, should the intake be changed at the same time? Honestly, while its been some 25 years since I last owned a carbureted engine, the Mercury intake looks pretty restrictive and I cannot see a new 4 barrel performing much better (other than fixing the idle issue). So the options, at least as I see them, are a Rochester and Edelbrock, a Holley and Edelbrock, or a new boat with a fuel injected motor. Thoughts? Thank you.

 

[Don S]

Re: Mercury 5.0L TKS Carb. Question

Why does your carb need such frequent rebuilds?? Don't you replace the water separating fuel filter yearly? Do you check it for water when you remove the old one?
If you have a water problem, it doesn't matter what carb you have. You WILL have problems.

 

[Don S]

Re: Mercury 5.0L TKS Carb. Question

To your question on carbs, the Edelbrock 1409 marine carb is the go to carb for conversions, but you also need a 4bbl intake manifold for your engine. An adapter plate is NOT an option. You also don't want an aluminum intake for a raw water cooled engine.

 

[Nashville]

Re: Mercury 5.0L TKS Carb. Question

To your question on carbs, the Edelbrock 1409 marine carb is the go to carb for conversions, but you also need a 4bbl intake manifold for your engine. An adapter plate is NOT an option. You also don't want an aluminum intake for a raw water cooled engine.

Thank you. Your point regarding the fuel/water filter is understood, and the filter is changed each fall during winterizing. I don?t understand why this particular carb. needs rebuilt/cleaned as frequently as it does other than it sits for about 6 months. (Fuel is purchased on the lake about every other week, is 91 octane per the pump sticker and is non-oxygenated?) But, when it starts to idle rough, if the carb. is rebuilt and cleaned, it runs fine for about another year. Do you have a recommendation for an intake manifold? I don?t see why aluminum wouldn?t work, this is a freshwater lake.

 

[Fun Times]

Re: Mercury 5.0L TKS Carb. Question

(Serial No. 1A606447)

FYI, You have an serious open service bulletin that needs attention and you should have received information of it in the mail. Service bulletin number 2010-12 - U.S. Federal Boating Safety Act REPLACEMENT OF POLYMER STEERING FLUID COOLER ON MERCURY MERCRUISER STERNDRIVE MODELS

Situation,
It is possible for the polymer steering cooler to break, allowing seawater to be discharged into the boat, causing the engine to overheat, and putting the boat at risk for swamping or sinking.
Correction,
Replace every polymer steering fluid cooler with the appropriate copper steering cooler at the earliest possible time.