20 min and it cuts out?

[Piratejay]

120 johnson V4 I can run the motor at dock no problem. I take the boat out and the after 15-20 min. I changed the sparkplugs, new fuel. And the motor is not hot, well it is hot but i can put my hand on it and leave it not burning me. I am confused at first i thought it overheated. Any ideas?

 

[steelespike]

If it just stops there may be an ignition part that fails as it gets hot. Get a spark checker and check spark when it quits.

 

[Piratejay]

Like one of the coil packs.. Got u. Yes it is the oddest thing it start to loose power then just dies out completely. It will start back up but only runs for a sec and not very sounding. That is what made me first think overheat, and the fact that it does not seem to be peing well. There i very little water coming out.

 

[emdsapmgr]

The guys have the correct info. Weak ignition components tend to fail-once the engine heats up to normal operating temps. If you shut if off and let it cool, it may start back up and run fine for 20 minutes, then fail again. When this happens, you can check for spark by cranking the engine over to see if the plugs have any fire or not. On the other hand, if the engine is suffering from a massive overheat, the engine can get so hot that the pistons will actually swell and lockup inside the cylinders. That's not really an ignition problem-just a massive overheat. Once this happens, the starter won't be able to crank the engine at all till the rotating assembly and powerhead cool off. You need to let us know just what type of failure you have.

 

[jakedaawg]

How long since you put an impeller in it? Use a guitar string or something to clear the tell-tale. If it doesn't have a strong stream then change impeller.

As for the cutting out, check spark once it dies. It still cranks over just won't start, right? Use a spark tester set at 7/16". Holding the plug to the block won't tell you much. A timing light will not tell you much in this case either as heat soak on bad ignition can lead to a weak spark that may fire the light but not the cylinder.

These v-4's should also have a compression check 1st, every time there is an issue. No sense spending time on one that has had a ring failure.

 

[Piratejay]

Ok ty lots of great advice. Yes i is the first one. It just cuts out and will turn over afterwords and kinda start but dies eminently. I do have a spark tester and will try that, plus u are right doing a compression test and get a base line.

Now the boat will not even really start as of getting stuck last night in the marco river. And same today. Rolls over but sounds like only 1 or 2 pistions are firing and cuts right back out.

As far as the impeller i just got the boat 2 weeks ago and it had not ran in 3 years. Rose marina supposably did the long term storage. And has done maintenance on the boat for years. They messed this motor up bad. I had to fix all kinds of nonsense they didn't either put back together or hacked together

 

[jakedaawg]

If it sat for three years an impeller is a must!

 

[oldboat1]

may turn out to be ignition, but get the model number and buy an impeller. When changing out the impeller, consider doing the t.stats as well. If it's a salt water motor, flush it thoroughly after reassembled if she's running, then check compression and spark.

 

[jakedaawg]

Yeah, do the compression test 1st, not after you spend money on parts. Just sayin

 

[Piratejay]

Where do i find the id tag for the model number so i can order parts? I can't find one any where? Johnsons are like foreign animals to me. I am use diesels, v8s, and Nissan's all the way up to 50 horse.