225 RPM Problems HELP

"I have recently purchased a b

"I have recently purchased a bay boat with a 225 mounted on it. Its more of a flats boat to give you an idea about weight. The dealership told me the engine should be turning 6,000 RPMs. The highest I've reached is 5,000 RPM. They said it was a prop issue? I started with a 21 pitch prop and only turned 4,400 RPM. Next, we tried a 17 pitch which only produced 5,000 RPMs. Afterwards, we tried a 19 pitch that decreased the RPM to 4,800 RPM. These RPMs are with the boat at full throttle and trimmed out perfectly. Should this engine ever reach 6,000 RPM? Non-expert people I've spoken to said it sounded to them as if one of the spark plugs have fowled or the engine is not running on all cylinders? Is there any truth to that? Any help would be greatly appreciated."

"It's most likely a prop i

"It's most likely a prop issue. First, how much does the boat weigh, what is it's length, and beam?

WOT for the 225 should be 6,000 RPM +/- about 150.

On my 25' C-Hawk, weighing approx. 4,000 lbs with a 9'6" bean, I use a 14.25 inch diameter, 15" pitch SS three blade prop. WOT = 5,900 rpm."

"The boat is a nautic star 240

"The boat is a nautic star 2400 tournament edition.

Length: 24'3"
Beam: 102"
Weight: 2500 lbs.
Max Weight: 2800 lbs.

To give you an idea about weight, I pull this boat with my golf cart from the condo to the boat lift."

"The 17" prop should have

"The 17" prop should have worked on that boat, given a prop diameter of under 15". However, before hauling the engine off to the dealer, try two things.

1. Beg or borrow a 14.25" or 14.50" diameter, 15" pitch Honda prop and try it out. (Lot's of time a dealer will have a bunch of spare props laying around that you can borrow for testing.)

2. Get a quart of Yamalub Ring Free, or similar marine decarbonizer for your gas, and run it through the engine.

Let us know the results.

If neither get's you up to 6,000 rpm, take it to a dealer and have them run the HDS diagnostics on the engine. That will pinpoint the problem if the engine is not performing up to snuff."

"Have you put yamalube ring fr

"Have you put yamalube ring free in your tank? I suppose if you have, then it wasn't harmful to the engine?"

"Not had to use it yet, but hi

"Not had to use it yet, but highly recommended. Local Honda dealer highly recommends it. Block on my 225 was replaced this spring under warranty after finding metal filings in the oil. Since then, I've been using ValvTec blended gas, which accomplishes the same thing. When I fill up with non-ValvTec gas, I'll drop 1/2 quart of Yamalub ring free in the tank.

Have previously used Sea Foam to decarbon an old Crusader 220 (GM 305). Worked great. Many folks around here highly recommend Sea Foam for decarboning outboards. A Commercial fishing neighbor who also is a Charter Captain uses Yamalub Ring Free in his 225. Claims very good results.

You may want to try Sea Foam. Follow the directions on the can for the shock treatment.

You can also get some good advice on the web. Search "Outboard Engine Decarb" or similar."

"The dealership is going to go

"The dealership is going to go run it again to see what the problem could be. I don't predict they will find the problem while running it, but I'll give them the benefit of the doubt. It sounds like they just wanted to get out of the shop for a little while.

Thanks for all of your help and I'll update you on the situation in a few days."

"W D Neal was right on on all

"W D Neal was right on on all counts...

I don't know your dealer, but they can do a cylinder drop test very easily with their HDS. That will answer your original question about a fouled spark plug.

They will have to do other tests to determine any mechanical issues inside the engine. They just have to go thru the paces."