95 speedster with idle varying between 2000 and 3000 out of water

[Bigmantony]

95 speedster with idle varying between 2000 rpm and 3000 rpm out of water. It starts with 3000 for about 30 sec or so then drop to 2000 or so then back to 3000 rpm. If I had a car with 4 or more cylinders I would say I lost spark in one cylinder. Spark going in and out. But with a two cylinder I would think it would just die. So spark problem or carb? New plugs gap to spec.

 

[Dr Honda]

What does it do in the water? But... Generally any time you have running issues... put in new plugs. Some 2-stroke engines will just eat them. At least you will rule that out.

 

[Bigmantony]

this boat you have look at before. when you check compression on it in 2010 august. mag 120 and pto was 165. when check compression cold mag was 150 and pto was 165 . after run it for 1 to 2 mins. recheck mag 135 and pto 160. did squash band .06 on mag and pto. i have your finding back then. do you want me to pm it to you.

 

[Dr Honda]

I just saw the PM... I kind of remember a 95 Speedster that I was originally going to clean the carbs, and change an oil tank, but I wound up not doing anything because the left engine needed some love.

Is this the boat we are talking about? If so... is this the same person, or did you buy it from the people in Pittsburgh?

 

[Bigmantony]

Bought it from the people in Pittsburgh. Change oil tank no leaks. I have anther engine, but trying to understand what's going on with this engine.

 

[Bigmantony]

Also when I prepare to start the starboard engine I found the water outlet at the rear of the boat clog with rust and sand. (The outlet you suppose to pinch off when running out of water.)

 

[Bigmantony]

Flush gas tank and sparks plugs aren't wet after running engines. Found one bolt missing from good engine carb hold down / mounting bolt. Starboard engine carb missing push back spring for carb choke butterfly on mag side. (choke would not close completely). Haven’t tested boat in water yet.

 

[Dr Honda]

I really didn't do any work at all. When I started it, and didn't like what I was hearing... I checked the compression, and when I saw one jug was high, and one was low... I just fogged the jugs, and put it to bed.

As I was saying in that email you got from the last owner... I think the left engine had the squash band set too tight, and the engine is eating itself. BUT... the last owner never had me check it. (they decided to not put any time or money into it) Now... that engine may be salvageable... but it needs to come apart, and be inspected properly.

 

[Bigmantony]

did you see my squash band measurement for the engine. the MAG side have .068 and the PTO side had .061 is that in spec? do you think that only the top half needs to be pull? could a engine cylinder borescope help?

 

[Dr Honda]

as I recall... it had "X" engines in it... and 0.061" is big. The spec on that engine is 0.035" to 0.051".

Yes... to top end needs to come apart. Regardless of what measurements we see... there is a huge range in compression. But, at least we know it wasn't too tight.

If it was my boat... I would pull the engine out, and take the top-end apart, and check EVERYTHING. The bore scope will only show you if there is damage in the top half., it won't be able to give you any measurements to figure out why you are showing the spread in compression.

Like I was saying, it's probably salvageable, but you can't guess at things at this point. If you do... you will probably loose the engine.

 

[Bigmantony]

Thanks for your input. If anyone has any ideals please post. I have 38 years in engineering with many types of engines, "but you can only learn if you listen to others". Have a nice day. I will post my findings.

 

[Bigmantony]

Dr. Honda here’s the results of engine inspection. Two bad pistons, one piston had lost one of its ring. The one cylinder with high compression volume has signs of piston scuff on cylinder wall. The cylinder with compression varying between 130 to 140 PSI was the piston without both rings. I’m replacing jugs, pistons and cylinder head. The head needed some cleanup work so I swapped it for one already clean. Later I'll post a picture of the bad piston soon.