2000 Islandia Low Top Speed/ Low On-Plane RPM

[CarewPat]

Hi all,

I've tried searching around and I haven't come across a similar issue so I'm hoping for a bit of guidance. I have a 2000 Islandia 240HP EFI

I'm having an issue with this boat. The issue is two fold. First, it takes some time to get on plane (sometimes). At WOT, the engine revs to 6700-6800, but takes between 10-50 seconds to get on plane. As it gets on plane, the RPMs drop as speed increases. It is inconsistent, but it seems to settle at 5500 RPM at WOT on throttle. It also doesn't run as smooth once at that RPM on plane. Is this inverse relationship between RPM and speed on plane normal? Top speed with 2 adults and a cooler was 30ish which seems slow to me.

What could be happening to cause this? At first I was thinking cavitation, but that would be consistent all the time. It wouldn't just go away once on plane would it? It seems to me that if the RPMs were at 6000-6200 on plane we would be achieving normal top speeds. Then I was thinking maybe a cylinder is dropping out under high load, but it stays at high load at WOT without much fuss, it's only on plane that issues occur. For reference, I have checked fuel pressure at WOT and it is around 38. I have replaced the spark plugs. I have checked the coils with a spark gap tester. All did around 11mm as per the specification in the manual. Ground checked the coils. Spec is .2 ohms. All were at about 1. This was out of spec, but all gap tested good. I resistance checked the triggers which appear to be relatively new. They were actually below spec. Manual calls for 1100 to 1400 ohms. With a Fluke meter, they all read 1000.

Hoping for some direction. Hopefully someone has experienced similar symptoms.

Thank you

 

[Tim75]

Crawl under and look at the leading edges of impeller blades. They should be smooth and almost sharp. Look at the wear ring while you are there. It should be smooth with no grooves. Look into the nozzle. You can barely see the leading edges of the front of the stator. Should be smooth with no dings or damage.

If you find damage, you will need to remove the stator and maybe the impeller to fix it.

 

[CarewPat]

Crawl under and look at the leading edges of impeller blades. They should be smooth and almost sharp. Look at the wear ring while you are there. It should be smooth with no grooves. Look into the nozzle. You can barely see the leading edges of the front of the stator. Should be smooth with no dings or damage.

If you find damage, you will need to remove the stator and maybe the impeller to fix it.

Got it. I took a look and I think you are correct. I think that explains the slow to plane problem.

I think the roughness on plane may be a different issue. Is it normal for RPM to drop as the boat gets on plane?

 

[Tim75]

Bingo! Problem found. As you raise RPM, the dull rough blade edges cause cavitation (air in the water) due to high suction. As the boat speed increase, suction decreases and the load on the engine increases and RPM drops.

I think you will need to remove both. There are "clips" available to repair the leading edges of the stator vanes. The hardest part is removing the nut on the impeller shaft. Also remove the grate. There are wrench flats there. DO NOT us an impact wrench on the bronze nut. Leave the wear ring in place while you remove the nut. DO NOT damage the end of the shaft. It is a seal and bearing surface. There is a thread at the top of this section about changing gear and stator oil. As soon an these two issues are solved, we can check your engine "roughness".