1987 Johnson 175 Slug

[Bocaccio]

I just took my boat out last weekend and it started fine and went up to top speed for about 5 min. After that it bogged down to about 6 mph at 2000 rpm. If I put the boat into neutral, I can rev it as high as I want, but when I want it to push the boat, it bogs down. I limped it back to the dock and am wondering what the next step should be.

 

[1730V]

Re: 1987 Johnson 175 Slug

DON'T rev in nuetral unless you want heavy metal parts flying at you.

You have, probably, a fuel issue.

Run the engine on a seperate (portable) tank, see how it does.

If it does better, your anti siphon valve, on your inboard tank is stuck.

Postback with results, we'll be here.

 

[emdsapmgr]

Re: 1987 Johnson 175 Slug

Spark check the engine to be sure your'e not dropping cylinders.

 

[mikesea]

Re: 1987 Johnson 175 Slug

possible water in gas,do you have a water seperator,its a good ,cheap investment and makes it easy to dx,if water is the problem,also check for tank vetaliation,or fuel line restriction,a spark test is a good place to start as well,but my experience leans to fuel

 

[CharlieB]

Re: 1987 Johnson 175 Slug

Ditto the spark test

DO NOT use neon lights in line for a spark test

I' pretty sure you are going to get a spark, but the problem is how much spark

A weak ignition system will allow revs in neutral but no power or revs in gear

The adjustable gap spark tester PROVES an ignition, good or bad, no doubt.