sportwin won't make full power

[xort]

I have a 1971 9.5 hp sportwin. It starts easily, idles smoothly and will rev way up in neutral but in gear it won't rev up nearly as high and consequently won't plane the dingy any more like it used to.
What's up?
Thanks

 

[Solittle]

Re: sportwin won't make full power

Welcome aboard!!

And what troubleshooting have you done so far?

 

[xort]

Re: sportwin won't make full power

sorry, subscribing to thread!

 

[xort]

Re: sportwin won't make full power

Troubleshooting? Just tried running the engine in neutral to discover it would rev well. Looked over the linkages and didn't find anything to be a real issue. The safety device that keeps from reving the engine while in neutral is disconnected so I hooked that up and it didn't make a difference.
Everything seems fine & smooth so I haven't done much except scratch my head.

 

[ezeke]

Re: sportwin won't make full power

The 9.5 will run on 1 cylinder with no load on it.

You need to determine that you are getting good spark at both cylinders. Then you need to perform a compression test to determine that both cylinders are in operating condition.

 

[xort]

Re: sportwin won't make full power

Will the 9.5 run smoothly on one cylinder? I would expect it to run rough...
I can check for spark tomorrow.

 

[ezeke]

Re: sportwin won't make full power

Take the plug wires off one at a time with no load and see.

 

[xort]

Re: sportwin won't make full power

Pulling spark wire did lower idle speed on each cylinder, seems to have spark.

Plugs look oily (dry) around the outer edge but dark tan at the tip.

Compression test shows 60 psi in one and 55 in the other with throttle set at full.

Do I need 100 PSI of compression?

 

[clemsonfor]

Re: sportwin won't make full power

First don't rev the motor up high in neutral especially higher than if you are running at WOT, unless u only make about 1200 rpn in gear. 60 psi sounds low and why it may be running bad in gear. Try to de carb the motor to see if it does any good if not pull the head and look at the cyl walls.

-nate

 

[ezeke]

Re: sportwin won't make full power

A thorough decarb and good thermostat will certainly help and you can also try running on a hotter spark plug, but the fact is that you probably have worn the piston rings out.

The 9.5 was always a little loose and it had three rings per piston. Over the years the carbon and rust seize the rings but the engine just will not quit. There are many running around at your compression readings that have been like that for years.

If you pull the cylinder head as suggested, make sure that you have a new head gasket first. I would do the decarb first as well.

There are several decarb techniques described in the engine faq forum on this site. I like the one attributed to Capt. Bob Dunkelberger [dunk75@comcast.net] where you add the seafoam to premix in a 3 gallon tank.

http://forums.iboats.com/bbBoard.cgi?a=viewthread;fid=36;gtid=1035563

More reading here: http://www.outboardrepairs.com/johnson_outboards_by_horse_power/?johnson

and here: http://www.outboardrepairs.com/evinrude_outboards_by_horse_power/?evinrude

 

[xort]

Re: sportwin won't make full power

Thanks for the info.
I read Bob Dunkelberger's piece. One thing I don't understand is the need for a new 3 gallon tank. I have a 3 gallon tank for my 9.5. It's almost empty so I could create the mix in that tank. Is there something I'm missing in regards to having a second 3 gallon tank?
Thanks again...

 

[itstippy]

Re: sportwin won't make full power

I think he's talking to folks with big boats with built-in gas tanks. Use the tank you already have.

 

[xort]

Re: sportwin won't make full power

I think he's talking to folks with big boats with built-in gas tanks. Use the tank you already have.

That's what I thought,
Thanks

 

[xort]

Re: sportwin won't make full power

I followed through on the Dunkelburger / Seafoam treatment. No change.
Motor will not make enough power to plane the dink.

 

[F_R]

Re: sportwin won't make full power

Will it run better with the hood off? Those motors are famous for getting smoke under the hood which kills performance.

 

[xort]

Re: sportwin won't make full power

Will it run better with the hood off? Those motors are famous for getting smoke under the hood which kills performance.

I have not tried that but I have removed the hood shortly after attempting to plane and did not get any smoke billowing out. Come to think of it, I did run the motor some in gear with the hood off and didn't notice any smoke.

 

[ezeke]

Re: sportwin won't make full power

If you have tried everything else you could try a lower pitch prop.

Even at the reduced power, the Michigan 3 blade #012068 that they sell here at Iboats gives a lot of thrust because of the 6.5 pitch. It will not do anything for the top end, but it could get you on plane.

http://www.iboats.com/mall/propfinder/

The high speed jet [orifice] lies horizontally directly behind the float bowl drain in the bottom of the carburetor, where it is sure to pick up any heavy solids and gum that collect in the carburetor. You might want to make sure that it is clear.

Ultimately, you have to consider new piston rings if you want that original power back.

 

[xort]

Re: sportwin won't make full power

Ezeke
Thanks, looking for the easy things to try before commiting to new rings.
I'm considering doing a carb rebuild but I'll take a look at the high speed jet first.
Anything else I should look at?

 

[iwombat]

Re: sportwin won't make full power

You might want to look at doing a basic tune-up.
Timing, point gap, new plugs, etc. Could be it's just out of tune. Between that, and a carb cleaning you'll soon know if the problem is a worn powerhead, or otherwise.

What prop are you running if I might ask. I noticed a big difference between the two props I have for my '67 sportwin.

 

[xort]

Re: sportwin won't make full power

You might want to look at doing a basic tune-up.
Timing, point gap, new plugs, etc. Could be it's just out of tune. Between that, and a carb cleaning you'll soon know if the problem is a worn powerhead, or otherwise.

What prop are you running if I might ask. I noticed a big difference between the two props I have for my '67 sportwin.

Engine runs very smooth at all RPM's so I don't think timing is out.
Pulled plugs for compression test and they looked good.
Haven't considered the prop. The boat planed fine earlier this year and the prop hasn't changed so it can't be the prop.
I do plan on attacking the carb first, before going at the rings.