Marine Sea Foam

Ranger09 · 2025-08-22T02:31:53-0600

I have a 2006 Skeeter 21icls with a yamaha 300hp 2 stroke. The boat sat for nearly a year, and I tuned it up. I changed the spark plugs, checked compression, changed fuel filter, oil water filter separator and lower unit oil. I never ran the boat wide open since I bought it a few years ago. I finally had a day to run it wide open and the best I could get was 62mph. The previous owner told me it would run over 80. Would it help to use seafoam to possibly help clean the carburetor and help get better performance? Never used it but not sure what direction to go to get the motor up to speed.

redneck joe · 2025-08-22T03:56:44-0600

There will be many that say seafoam is a waste of money, I'm a believer however. For 8 bucks why not try? Last time I used it was on my pressure washer that had not been run in at ,east four years and had fuel in the carbs when put up. After two tankfuls it was able to run without the choke being at least halfway on.

What it your WOT rpms and what year motor?

redneck joe · 2025-08-22T03:57:43-0600

And assuming all fresh fuel?

Scott Danforth · 2025-08-22T04:39:26-0600

sea foam wont clean a carb.

what RPM are you getting on the motor. if its running lean, that is a good way to toast a motor.

I would use ring-free to make sure the rings are loose.

Grub54891 · 2025-08-22T05:03:09-0600

Sea foam "might" work. Also, you have to add enough for the amount of fuel you have. A car is usually around 20 gallons. A boat may be much more, it wont hurt to try it but removing/rebuilding is the route I would go. Also anyone selling may say things to make you think it's better than it is. 80 mph is rather fast for a stock motor I think myself.

cyclops222 · 2025-08-22T08:21:58-0600

Are we serious ? Difference in HP to go to 80 mph from 60 mph in a 21' old boat ? Post this question in a real Bass Boaters forum to get reality RPMS of engine and boat. Boat has soaked up water ? Prop is wrong or damaged. Is the engine wearing a 300 hp cover. 20 years of what kind of maintenance ?
Start with the sparkplugs. Right type number, gap.
Bass boats are run at 2 speeds. ONLY

Ranger09 · 2025-08-22T10:11:10-0600

redneck joe said:
And assuming all fresh fuel?

I only use ethanol free with yamaha ring free in every tank. Its a 2006 motor and have no idea what the previous owner used.

Ranger09 · 2025-08-22T10:14:27-0600

Grub54891 said:
Sea foam "might" work. Also, you have to add enough for the amount of fuel you have. A car is usually around 20 gallons. A boat may be much more, it wont hurt to try it but removing/rebuilding is the route I would go. Also anyone selling may say things to make you think it's better than it is. 80 mph is rather fast for a stock motor I think myself.

Thanks, I think I jumped the gun buying a boat thinking if its a 300 I got something most dont. Live and learn.

airshot · 2025-08-22T10:25:18-0600

Very few boats can actually do 80 mph, sounds more like a sales pitch !

99yam40 · 2025-08-22T10:56:11-0600

look up Yamaha performance Bulletins for a boat and motor like yours and see what prop, RPMs, and MPH they listed to compare

redneck joe · 2025-08-22T11:53:24-0600

Yeah what i saw in my search was low 70stop end so you might be close. 80 the PO told you prob is like mag stickers on new vehicles.

boscoe99 · 2025-08-22T13:18:14-0600

There are no carburetors on any Yamaha 300 HP two stroke models.

tphoyt · 2025-08-22T14:33:31-0600

Running 80+ is mentally and physically challenging. It was for me anyway. The fun factor gets old pretty quick.
Be happy with the 62.

redneck joe · 2025-08-22T16:06:15-0600

I had a boat that did 72, I drink too much for that. Sold it quickly after the fun wears off.

flashback · 2025-08-22T19:41:04-0600

Are ya using GPS for the speedo?

Ranger09 · 2025-08-23T03:57:19-0600

Thanks for all the input. I will check my RPMs next time I am out and get back to you all.

Ranger09 · 2025-08-23T04:30:11-0600

flashback said:
Are ya using GPS for the speedo?

yes

Ranger09 · 2025-08-23T04:34:40-0600

Grub54891 said:
Sea foam "might" work. Also, you have to add enough for the amount of fuel you have. A car is usually around 20 gallons. A boat may be much more, it wont hurt to try it but removing/rebuilding is the route I would go. Also anyone selling may say things to make you think it's better than it is. 80 mph is rather fast for a stock motor I think myself.

That's what I'm thinking. If it comes to that it's going in the shop.

bajaman123 · 2025-08-23T04:47:08-0600

Seriously, as noted above you need to really have an understanding of the WOT limit of the engine, the gear ratio, and prop pitch to determine what your top speed will be. You simply say you have never run WOT. First of all...why not? Or is it because it WOULD not? To put it succinctly, you either have an underperforming engine with the right prop or you have way too much prop with a properly performing engine.

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