Bad Engine Day

[jagilbert]

95 Speedster, twin 657x, noob at the helm and keyboard.

I had both engines go out on me yesterday. They were both fine the prevous time I went out.

Port Engine: I guess its cavitating - revs pretty quickly up to the rev-limiter at about 7000rpm, but very little thrust. I see bubbles in the small clear hose on the head and they indicate that there is little or no water flow. After a few minutes of fiddling with it, the overheat alarm sounded and I shut it down. The time before last, I sucked a rope into this impeller. I took the pump off and removed the rope. There was no obvious damage to the prop wear ring or shaft. It seemed to run fine the next time I took it out... Or did it. Now that I think of it, that engine did seem to redline pretty easily out of the hole before it got "traction".

Stb Engine: The pto-end cylinder isn't firing until I rev to about 4000 rpm. Tried swapping plugs with the port engine - no difference. I'll do a compression check when I get home tonight.

:ack: Any thoughts on either problem?
-Jeff

 

[jagilbert]

UPDATE:
The stb engine is only running on the mag-end cylinder. At the lake, the other cylinder would kick in at about 4krpm
Compression is 140 in both cylinders. Thats a relief. It runs equally well(poorly) when I put either plug wire on the good cyl, and doesn't run at all when I put either plug wire on the bad cyl. (That works because I understand both plugs are timed to fire at the same time)
So that leaves fuel. Do I need to order a carb rebuild kit, or is there something easier I can check first?

The port engine was overheating.
It seems to run fine on the hose, with water entering at the host fitting and exiting from the large hole on the transom, through the exhaust, and through the pump via what I assume is normally the inlet line. There is barely a trickle out the pee hole. The other engine also doesn't send much to the pee hole either, which, I gather is not too surprising or concerning. I only ran it for a minute on the hose so as not to damage the shaft bearing.
So why was this engine overheating? It was definitely cavitating. I recently removed the pump to remove an ingested ski rope. Did something get damaged in there causing it to cavitate so bad as to not be able to push cooling water to the engine?
What do I need to check?

Any suggestions would be welcome.

Thanks,
Jeff

 

[Dr Honda]

You probably need to go though both sets of carbs... but since you have spark, and compression on the Stb engine... I'd say you have a carb issue there. You don't necessarily need a "kit" to clean them. But, once you are inside of the carbs... if you need parts... then you may need to order it.


On the port engine... you have a large air leak. Most likely it's around the driveshaft seal. I would rebuild or replace both seals. (stb and port) That engine is over heating is because you need to build water pressure in the pump to be able to feed water to the engine. So... bad cavitation will lead to overheating.


With the problems you are talking about... don't keep running the boat. You could kill the engines.

 

[jagilbert]

Thanks Dr.!

I've ordered these carb rebuild kits.

Can you suggest what I need to rebuild or replace the driveshaft seals? Do I need a carbon type, or the other kind? I see a zerk fitting just visible under the pto cover if that matters. Does it make sense that I might have trashed that seal when I injested the rope?

Cheers,
Jeff

 

[jagilbert]

Well i tore down the stb carb, and cleaned it out. Reinstalled and it seems to run fine on both cyls now. Yea!

I took the port pump off to look for leaks and found a new piece of debris tangled around the shaft. Yea!

We'll see how it runs on the lake tomorrow.

Case Closed.
-Jeff