15 hp 2 stroke, Recovering HP

[Fr3AkAzOiD]

I have a '99 Merc 2 stroke 15 hp on my Watermouse and I'm trying to recover any hp that has been lost over the years of use.
It spent it's first 3 - 6 years as a rental so one can only guess the type of maintance it received. After that it's been in two or three owners hands before I got it.

I've ran Seafoam through it and it coughed out chunks of carbon and a good deal of smoke. I replaced the sparkplugs and found the ones I took out to be a bit out of spec 0.078 instead of 0.060. I've lubed all the moving parts and changed the lower unit oil as well as replaced the impeller.

It's running well within the rpm specs of 5,000 - 6,000 at 5,430 but I'm hoping to get a few more rpms out of her.

I'm wondering what else I can do to bring it back to peak performance?

Thanks in advance

 

[Sea Rider]

Re: 15 hp 2 stroke, Recovering HP

You could run half can of Power Tuner through engine to remove carbon deposits on pistons, rings, just follow instructions. If that's a rebadged Tohatsu 15 the plug gap is 1.0 mm.

Happy Boating

 

[Fr3AkAzOiD]

Re: 15 hp 2 stroke, Recovering HP

I don't think it's a rebadged.
Manual says 0.060 inches (1.5 mm).

 

[Mi duckdown]

Re: 15 hp 2 stroke, Recovering HP

If 5430 rpm is correct. You pretty much at peak performance. What does your prop look like. And are you sure 6000 rpm is max, not 5800. you can only get so much out of a 15 hp

 

[Fr3AkAzOiD]

Re: 15 hp 2 stroke, Recovering HP

6k is max, verified by the manual.
Brand new 9.25 x 11 SS prop, old 9 x 9 alum was over reving a little (6100 rpm) as I'm a lightweight..

I understand I can only get so much out of a 15. I'm just wondering if after 13 years is it even making 15 hp anymore?

 

[carholme]

Re: 15 hp 2 stroke, Recovering HP

After 13 years there is going to be normal wear and tear in anything but the first thing to do to see where your power is at is a compression test.

Gerry

 

[Fr3AkAzOiD]

Re: 15 hp 2 stroke, Recovering HP

I don't know much about compression tests but I thought they would simply point out if there was a problem with a specific cylinder by way of the difference in psi between them.
As long as they were both close it shouldn't matter if they are both 93 or both 105, is this correct?

Just wanted a general understanding before taking it in to get tested.

Would it be worth rebuilding the carb or is that something that you wouldn't really mess with in this situation?

 

[Sea Rider]

Re: 15 hp 2 stroke, Recovering HP

If runing good why rebuild carb, probably place new plugs, go for a compression test, will tell you where you are standing, instead of wild guessing interior engine condition...

Happy Boating

 

[carholme]

Re: 15 hp 2 stroke, Recovering HP

Here is a link to the compression test:

http://forums.iboats.com/showthread.php?t=391323

Yes, it will show a specific problem between cylinders or it can also show low overall compression. No matter what, low compression overall or single cylinder problems are going to reduce the power the engine is capable of producing. It's like breaking a leg, you may still be able to hobble about but you will never run as fast as you can on two good legs.

Good luck with it.

Gerry