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Ask Dominick Your Own Question
Dominick, Marine Mechanic
Category: Boat
Satisfied Customers: 1009
Experience:  25 Years Experience as Mechanic, 20 Yrs Boat Yard Owner/Mechanic, Factory Certified
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I have a 04-GP 1300R / it's the first weekend out in a year.

Customer Question

I have a 04-GP 1300R / it's the first weekend out in a year. It has a SBT-rebuilt motor put in last year. It's sluggish, first weekend out this summer. Feels like it only has 2-cylinders running. It got up to 60+ once,now won't go past 30. We swapped plugs. We saw all cylinders moving. Nothing frozen. One of the plugs looked like it was running a little lean. But still digging. Is it a injection issue?
Submitted: 1 year ago.
Category: Boat
Expert:  RSRBOB replied 1 year ago.

Hi and thank you for your question.

I suggest checking the compression right away. We need to ensure the engine is mechanically sound before going too far. Also, certain SBT engines have a warranty on them and if yours is still under warranty, they don't want you taking it apart, so we need to do some diagnostics before ripping into it.

While you are doing the compression test, you can put test spark plugs back in the spark plug caps and make sure it is sparking on all 3 cylinders. BTW, you will need extra spark plugs because you need to leave the other 2 spark plugs installed in the head as you check compression. Do not do the compression test with all the spark plugs removed.

How many hours did you get on the SBT?


Customer: replied 1 year ago.
Less than 20. It's already been well over a year, we just haven't had much of a chance to take it out.
I'm at the lake. If I'm checking compression. Is there really anything I can do here? But what tool would I need to check compression? I'm not a mechanic but I do all my work on my old car and truck. So might as well learn how to work on the pwc.
Expert:  RSRBOB replied 1 year ago.

Thank you for the additional information.

To answer your question about if you could do anything at the lake, no. The compression test is the most basic of all diagnostic tests however. With the symptoms of only running on 2 cylinders, there is little hope of salvaging the weekend. Sadly, there is nothing simple such as a blown fuse or something like that to cause the symptoms of one dropped cylinder.

There is quite a lengthy list of potential causes for the symptoms you are having, but none that come to mind as most the probable causes that are an easy fix that will save the weekend. Anything that would be a quick easy fix would likely affect more than one cylinder, so that isn't encouraging either. Sorry for the bad news but it isn't looking too good.