engine tuner or re-build???

Engine: '75 Johnson 15<br />Problem: 45 pounds of comp.<br /><br />Would it be better to tear down the engine, remove all the carbon from piston/rings and exhaust housing (and possibly replace rings and hone cylinders) <br /> OR<br />Spray some seafoam, engine tuner etc. and see results..<br /><br />I also wanted to take a look the thermostat and the reeds.<br /><br />Any possible suggestions?

Re: engine tuner or re-build???

tune spray is like 6$ a can try that first it works great

Re: engine tuner or re-build???

If everything else is ok why not. Spray, let sit overnite then start up. Stuck rings etc. that are unstuck work wonders.

Re: engine tuner or re-build???

Also make sure if let sit overnite you spray a little lube(fogger, wd etc) in each plug before starting. Just a precaution. Make sure you have either muffs or in the water to keep the motor cool and would not hurt to add some sea foam to the gas. <br /> Is it over heating? If not why the thermo? <br />If still no compression then probobly check reeds etc. Old motors new/old problems.

Re: engine tuner or re-build???

Interesting stuff, boyseen makes power reeds for outboards. (I'm not sure about my model) Though these 9.9 and 15's haven't changed much at all over the years. Though 45 psi of comp. It feels like more, but I guess I don't know what a fresh pullstart outboard feels like.<br /><br />I haven't done any water trials yet. I'm working on my aluminum boat. It idles fine ( I played with the mixture a bit to hopefully stop it from missing) and small amounts of power (in a garbage can) are handled. Though, I worry that it will suck at WOT. And that's where most of the power is anyway.<br /><br />Thanks a bunch.<br /><br />I'll try the sea foam stuff. There's some pretty nasty non metalic eating stuff in there, but I guess it is designed for the marine industry anyway. (Gee, it oughta make my backyard pretty blue and black!)<br /><br />I also have heard that the newer thermostats are made better. Possibly if they produced one that when it failed, it stayed in the open position, that would be a boat saver.

Re: engine tuner or re-build???

Hi cartoper....follow the directions on the Seafoam can for decarbing. Some products for decarb only recommend a certain time. Engine tuner from Bomby recommends up to 16 hours. Some stronger products may hurt the plastics around the water pump area or gaskets. <br /><br />I have yet to find a t-stat that would fail open. They can fail either way. Good luck with the decarb and keep us posted.<br /><br />By the by.....boyesen reeds will fit yer engine. 'bout $25 for the set.