Requesting advice: Power loss & cavitation solved...sort of

[lgparra]

So after receiving my boat back from the dealer for the initial 10-hour service I was out on the water and I couldn't get the engine to rev above about 6200ish RPM's. My initial thought was I sucked something up. Did the cleanout port dummy checks but nothing was apparent. Dug a little further and found my throttle cable wasn't tight against the stop. Adjusted that quick but was only able to get up to about 6500ish RPM's. Dug a little further by checking the spark plugs, correct gaps, torqued properly, etc. And then I got to checking the oil level. Come to find out the dealer way over-filled the oil . The oil level was a considerable amount above the high mark. I ended up sucking out about 2/3 of a quart of oil and now the oil is pretty dead center between the high/low mark on the dipstick. Took the boat back out and was able to get up to 7500-7600 RPM at WOT. So I think the power loss part of it is solved. However, I am still getting some pretty bad cavitation when taking off (not slamming down on the throttle but just taking off to get up to speed from idle). While looking in the intake grate I found a pretty sizable chunk of sealant sticking out. So my question to you guys is should I perhaps remove the grate and carefully cut it off that excess sealant with a razor blade? I don't know if it's the cause of cavitation but I'd have to imagine it's disrupting the flow into the jet if only a little bit right? Thanks guys!

 

[Ericd]

I think of the intake tubes like a wind tunnel. There’s a huge flow thru there and with the impeller turning at 7,500 rom even a small wood chip can shut the propulsion system down. So, yes, clean the silicon up and see how she runs!

 

[Ronnie]

i think the loose Sealant is causing the cavitation. I recommend you cut the loose piece off and see if it helps. If it doesn’t you will need to fill the gap with the goal of making the intake path as smooth as possible. You can try putting new sealant on top of the old stuff just to see if Filling the gap resolves the problem but ultimately you may have to remove all the the old sealant before resealing the pump. Unfortunately, I’m speaking from experience. That is, I’ve been there and done that. Tools you will/may need: razor blades, 3m 4200, socket wrenches to remove the impeller/pump/shaft/nozzle assembly, Dremel with cut off wheel and sanding barrels. Good luck.

 

[anmut]

i think the loose Sealant is causing the cavitation. I recommend you cut the loose piece off and see if it helps. If it doesn’t you will need to fill the gap with the goal of making the intake path as smooth as possible. You can try putting new sealant on top of the old stuff just to see if Filling the gap resolves the problem but ultimately you may have to remove all the the old sealant before resealing the pump. Unfortunately, I’m speaking from experience. That is, I’ve been there and done that. Tools you will/may need: razor blades, 3m 4200, socket wrenches to remove the impeller/pump/shaft/nozzle assembly, Dremel with cut off wheel and sanding barrels. Good luck.

I think if he has to go that far, it's "drop off for warranty work" time.

 

[Ronnie]

I think that if this is treated as a warranty claim the boat will sit in the lot for at least a month and the dealer may still not be able to identity the problem or solution (there is nothing in the shop manual that I have which even describes what it means to properly seal the pump but my manual is close to 10 years old, it’s a 2012). Summer is almost over, especially if you are in school or have kids in school, i would not want my boat sitting in a shop for the last part of the season, unless I lived somewhere that I could boat year round.

 

[rad1026]

So reducing the amount of oil made that much difference. I know my 2016 runs around 7250 starboard 6850 Port and both engines oil levels are right to the top of the upper mark. Maybe I should remove some oil and see if that helps.

 

[HangOutdoors]

So reducing the amount of oil made that much difference. I know my 2016 runs around 7250 starboard 6850 Port and both engines oil levels are right to the top of the upper mark. Maybe I should remove some oil and see if that helps.

Yes put it down to less than half. I run mine at just a bit over 1/4 of the way between L and F and I get Max RPMS. When I did an experiment and recorded findings and my different levels, I would bleed of at least 500 rpms plus. at Full. Check warmed of course.

 

[lgparra]

Hey thanks for the input guys! I ended up being able to squeeze my arms into the intake grate with a box cutter are carefully trimming that excess sealant without taking the grate off (didn't really want to mess with re-sealing and loctite-ing the bolts if I didn't have to). Won't be able to get out on the water till early next week but hopefully it'll solve or at least help with the cavitation issue.

 

[lgparra]

So reducing the amount of oil made that much difference. I know my 2016 runs around 7250 starboard 6850 Port and both engines oil levels are right to the top of the upper mark. Maybe I should remove some oil and see if that helps.

I was surprised myself too. I'd read elsewhere on the forum that too much oil will really drop the RPM's in these motors so figured I'd give it a shot and it helped a ton. In my case, it was probably a little on the extreme side. Like I'd said the dealer really over-filled the oil. With the motor warmed up and the engine level it was considerably higher than the high mark on the dipstick.

 

[HangOutdoors]

I keep telling people Don't Trust The Dealer Service Department and check your own oil levels after they do service. It happens time and time again. Also when your oil is high you should check the air filters for saturation.

 

[rad1026]

I have checked my air filters and they look great, but my oil only shows right at the top line. Although, come to think of it, I have never checked it with the engines warm. I will do that for sure.

 

[HangOutdoors]

With the engine warm my levels rise a bit.

 

[lgparra]

I keep telling people Don't Trust The Dealer Service Department and check your own oil levels after they do service. It happens time and time again. Also when your oil is high you should check the air filters for saturation.

Yep the old adage "no one else will ever take care of your boat like you take care of your boat" is certainly true in this case. Figured I'd have the dealer just do the initial 10-hour but from here on out I plan on doing all of my own annual maintenance.

 

[lgparra]

Follow up question cause I'm genuinely curious but I never really took note of it while driving. Should or will my max RPM's at WOT change depending upon how many people are in the boat? I know top speed will obviously decrease but should I be seeing say about 7500 RPM's WOT regardless of whether there is 2 people vs 8 people in the boat?

 

[Seadeals]

WOT rpm does not change. The pumps put out the same rpm/thrust. F=MA and the mass (M) is higher so with constant force acceleration is slower. The drag is also higher so rope speed is lower.

 

[Ericd]

You should see same top rpm, but it may take a lot longer to get there (because of extra weight) and you won’t be going as fast. Think about it like this - 200 hp (7500 rpm) yields 50 mph w 2 on board, same 200 hp (7500 rpm) yields 45 mph with 8 onboard - heavier boat to push thru water

 

[wishnyouwerehere]

My guess with your oil level, when they drew the oil out they did not get it all. Then they pour 4 quarts on top of it and bam, its overfilled. I dont even want to mention how I know this can happen!

 

[HangOutdoors]

The other thing is that people put in what they take out. But if it was high before you took it out and measured it will be high when you put it back in.