Loss of power after sustained run

[relaxed101]

OK experienced gurus, how's this one...

1990 Johnson 70 VRO (VJ70TLES8) good old two-stroke that runs solid, usually pulls the kids on tube or boards. Tops out at 5400RPM but rarely do that much. This past weekend put it in the inter coastal. Ran between 5000-5200 for 10-15 minutes at a time, then idle for slow zones. When I tried to take back off, it would only reach 2000RPM. Also, it didn't sound "right", almost like it was getting too much gas. I'd shut it down, trim the motor out of the water (don't think that did anything, but the wife insisted). When I'd restart it (it started right off fine) and gave it throttle again, it would sputter and surge for 10-20 seconds, then pick up and run fine.


I assumed it was a fluke, but it did the same thing 3 times. By the second/third time, I could tell by the sound of the idle that it was going to bog down. I'll put it in our lake later in the week and see how it runs, but it did fine each time after it finally picked-up.

I'm thinking carburetor, possibly float or needle... Any thoughts?

Thanks,

[ChampioNman]

First thing to do is check compression, if that checks out, then check the throttle linkage to see if one of the carb arms may have kicked out of their socket. Verify all of the butterflies are opening correctly. But it sounds like the PP has finally given up the ghost.

[relaxed101]

Maybe it finally gave out, but compressions 2 months ago were 125's on all three holes. I like the throttle linkage idea, cause when I got home, in the driveway on a hose it ran fine but was idling high, like something was sticking in the throttle. Plus, it only seems to give me a problem after the longer runs, did fine (even at the end) on shorter runs.

[ChampioNman]

You can always pull the drain plugs on the carbs, pump the bulb, flush them out and re-install the plugs. Flush the belly pan out with H20 and no

[ezmuny13]

my 2000 150 johnson done the same thing 2 weeks ago powerpack

[relaxed101]

Dang, I'm afraid ChampioNman and ezmuny are right... I hooked up a pressure gauge and got 40 psi out of #1 and 110 out of the other 2. Plus, saw a little water in the first cylinder... Which seems silly 'cause it started and idled so smooth, but probably won't pull too strong (I'm gonna drop in in the water Friday just to see what it does).

I'm imagining my options are replace the powerpack, get a similar (2-stroke) replacement outboard or throw some more money at it and get a 4-stroke. I don't see a lot of used 4-strokes around, any idea where I might get a "cheap" 90-100 used 4-stroke (or am I asking too much), or how much to replace the powerpack on my 70 horse?

[RUSTY63]

Just a question, look at the overboard discharge hose (pee tube) where it comes off the exhaust cover, does it connect at the lower part of the cover and run straight out of the pan?

[relaxed101]

The pee tube goes from the starboard side, around the back and into a plate on the port side (is the bottom tube in the port pic), can't see where it goes after that. Here's a pic of the starboard side also (if that's any help). It's seems with low compression on one cylinder that the entire engine is shot, but if it's the power pack, I see these things for under $100. Must be some serious labor... I need to get a manual for this thing.

[RUSTY63]

From the pic it looks like the hose runs straight out, this could be the reason your motor failed #1 cylinder as the cooling water will run out of the cowling before it fills the block.

The overboard discharge hose should run from the exhaust cover up over the top of the cylinder head down the other side and then exit the lower pan.

There is a service bulletin about drilling the upper part of the block and adding a fitting, you can achieve the same results by running the hose up over the top of the head.

[ChampioNman]

Nice pick up John . Forgot about that one

[rudetech1]

Use the water pump kit #432955, it has all the necessary fittins' you will need, you may need a longer hose for the overboard indicator. Increase the size of the high speed jet, at least two sizes up. This will allow for more fuel and oil to help you keep the innards cool.

[relaxed101]

Just a note... I might have gotten lucky. Looks like the head gasket is toast at the top, might have just burnt that up. Will replace, add the longer hose and put it over the top. I'll check out that water pump kit to keep it cooler. I'll let you know if the gasket helps the compression on #1.

[stratos22ssextreme]

Shoot I wished I was that lucky, when I checked comp. on #2 of my 2000 225 ho it was lower than the rest, A local tech said pull the head :1 no damage, maybe a blown gasket. :2 damage you got BIG problems. mines the #2. Pin in ring groove backed out and broke or needle bearing came out of retainer & floated in#2 cyl. and went for a ride. Needs a bore and sleeve job, head and piston. I'm sick Saving up to have it done RIGHT !! I'm a mech. on Gradall's & have a background in machineshop on Mazak. It cost for a good mech. to fix it but it will be done right.

[ChampioNman]

Andy,
Bring it over to me. You'll be right when I get done with it and 1/2 the cost. Can have you up and running in about 2 weeks. Do them all the time.

[RUSTY63]

If #2 went on this motor it must have been warm a few times.

[relaxed101]

Am I LUCKY or what?!? It was the head gasket with a hole blown in it (around cylinder #1). I replaced the gasket, ran a longer water hose over the top of the head and test ran it. The water leaves in a solid stream now, now the sputtering it used too. Pulls out of the hole like a rocket (at least as much of a rocket you can get from 70 horse). Gets me 4 more mph at 5500 RPM and shows 110 psi on all three cylinders. I know it's only Monday... but I need a beer!!! Thanks for all of the info... again.