RPM drops right after WOT.

[Joey_E]

I actually have a boat but posting it here since it's the same engine as the ski's and most of you guys are in this sub-forum.

Right after WOT (in 6200ft elevation lake at 68degF water) it goes to 8150rpm for a second but then drops to 6800 and stays there for my max RPM. My SC is producing boost, tested it by pressing on the intake hose and I can feel it expand after giving it throttle and it has only been less than 20 hours since it was rebuilt with steel washers. Re-checked slip on the SC once thinking it was the problem but it was all good. Oil level is between the bends on the dip-stick. Spark plugs are good. All hoses seem to be tight and intact. I just replaced the TPS and zero's out with my CanDoo but that too did not fix the problem. No error codes are given on the cluster or with CanDoo.

Specs:
Challenger 180SE 2007 215hp(all stock) except 14/19 original impeller was replaced with a 13/18 Solas to compensate the loss of initial pull at high elevation.
4-tec engine, Internal Intercooler,
Elevation 6200 (Lake Tahoe)

I am thinking of getting a new ECU but it would suck to spend that much and still won't fix it. What do you guys think? =(

 

[pvamax]

If I'm reading this right, you now have a 13/18 solas? Stock is a 10/21 but different manufacturers measure differently so the numbers aren't comparable. I know a stock boat at sea level works good with the 13/18, so you may still have too much impeller. 3hp loss per 1000ft so instead of a 215 boat you actually have about a 197hp boat. How many people in the boat when you are seeing 6800?

 

[Joey_E]

I thought stock for this year model is a 14/19 pitch. I tested it on the lake this morning after installing the new TPS with just me on the boat, 15 gallons of fuel and a secondary house battery. I knew it now runs less than the advertised 215hp but does 197hp equate to 6800rpm that I'm getting?

 

[pvamax]

Fuel octane? Oil overfilled? Halfway up the dipstick is the target.

 

[Joey_E]

Fuel octane? Oil overfilled? Halfway up the dipstick is the target.

Fuel is always 92 octane and the oil level is mid-way between the bends in the dipstick.

 

[pvamax]

I thought stock for this year model is a 14/19 pitch. I tested it on the lake this morning after installing the new TPS with just me on the boat, 15 gallons of fuel and a secondary house battery. I knew it now runs less than the advertised 215hp but does 197hp equate to 6800rpm that I'm getting?

I would not be surprised to lose that much rpm due to elevation. The initial surge of rpm is likely cavitation. Wear ring replaced lately?

 

[Joey_E]

I would not be surprised to lose that much rpm due to elevation. The initial surge of rpm is likely cavitation. Wear ring replaced lately?

Wear ring is in great shape. It actually goes to plain fairly quick. I can only go 30mph or a little faster on a good day which fairly corresponds correctly at 6800rpm's based on my reading for this boat.

 

[pvamax]

Wear ring is in great shape. It actually goes to plain fairly quick. I can only go 30mph or a little faster on a good day which fairly corresponds correctly at 6800rpm's based on my reading for this boat.

Must be mph on the gauge, not gps? Gauge not very accurate and that seems very low for 6800.

 

[Joey_E]

Must be mph on the gauge, not gps? Gauge not very accurate and that seems very low for 6800.

It's using gps off my Garmin depth finder

 

[Joey_E]

I found these charts a while ago for the C180SE.

 

[pvamax]

It's using gps off my Garmin depth finder

To me, the surge of rpm tells says it's cavitation then it hooks and brings down rpm. If wear ring is exquisite, I'd be looking for other causes like ride plate seal and carbon ring. You might even get less rpm once that's straightened out, but more mph. Sc rebuilt recently? Pull intake house and Check sc veins to see if it turns easily by hand .

 

[pvamax]

I found these charts a while ago for the C180SE. View attachment 41337

I guess that makes sense then. Mine sees 48mph gps at 7800 and roughly 40 at 7000, so not what the chart says but it's off the same amount at both rpms. Those numbers are close to what id see with 6 adults and coolers onboard.

 

[Joey_E]

I guess that makes sense then. Mine sees 48mph gps at 7800 and roughly 40 at 7000, so not what the chart says but it's off the same amount at both rpms. Those numbers are close to what id see with 6 adults and coolers onboard.

Did you do any mods to make it run better?

 

[pvamax]

Did you do any mods to make it run better?

Bone stock.

 

[Joey_E]

Bone stock.

215 or 255?

 

[pvamax]

215 or 255?

215.