new to me

[gotmeaboat]

1994 Hydro-Sport 1850 with a 1994 Johnson 150 Ocean Runner. on the trailer it starts, idles and runs great. took it out saturday and would run 3600 rpms and when i drop back to 3000 it would continue to drop to about 400 and then would die. at the dock it would idle at 700. i just bought this boat. any suggestions?
thanks

 

[Fl_Richard]

Re: new to me

That engine is crying out for service. I wouldnt run it until you fix it or it could get really expensive to fix. It should run 5800 RPM at WOT.

 

[jonesg]

Re: new to me

Its not running on all cylinders, don't go out til you fix it,
get the shop manual, compression guage and spark gap tester.
www.outboardbooks.com
Don't buy seloc or other third party manuals.

They run good on the trailer because theres no load, a spark tester with adjustable gap would have showed the dead cylinder, even a timing light will do it.

I have the same year 150hp, I didn't put it in the water until we had gone through it top to bottom.
All it takes is a dirty or gummed up carb and you can fry a piston in minutes.

Find the dead cyl , swap the coils to see if the problem follows the coil.
Compression should be 70psi+ and even.
Examine the plugs and post back.

Compression guage and gap tester will only cost $40 from the auto parts store.

 

[gotmeaboat]

Re: new to me

took the boat to the shop last night. checked compression and all were right at 110. changed the plugs to the proper plugs. checked spark and all were good. looked at the prop. there was a four blade 14 x 21 on it, we replaced it with another prop we found in the console, it is a three blade 14 3/4 x 17. how bad would the 4 blade make the boat run? 1994 18.5 Hydra Sport w/Johnson 150hp.
tom

 

[jonesg]

Re: new to me

Ask about the props in the prop forum, its a black art to me.
Those 4 bladers are expensive, thats all I know.
Use the right Champion plugs or risk a blown cylinder.