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Mr1 missing or dropping cylinder at wot

Jgorm

Jetboaters Captain
Messages
1,286
Reaction score
907
Points
207
Location
San Diego / Colorado river
Boat Make
Yamaha
Year
2004
Boat Model
AR
Boat Length
23
I bought this ski to replace an engine in my boat. Now the ski is giving me trouble! You guys are real smart and your feedback is appreciated. This is what I posted on green hulk.
I picked up a used ski with 95 hours on it. New plugs and oil change. Compression is good ~180+ cold, 220+ hot. I checked the oil level well over 10x and it's right in the middle. New air filter after the oil level was verified after multiple rides.
The first issue happened about 15 miles down river in an area with very few boats. We floated by the ski for about 20 minutes while holding the rear u bolt. The wind was blowing upriver so I had to continue to tug it down. We put three of us on there and it wouldn't start. We bright it to shore and removed the filter and it started right up. I think there was water build up in the exhaust and it was too much pressure with 3 people causing it to ride low.

The first day it seemed to do about 50mph at about 10k rpms. Now it seems do do 40-45 at between 9000 and 9500 rpms. Sometimes it stutters a bit at wot, like you let off the throttle a split second. I took off the metal filters and cleaned them with carb cleaner. Air filter still looks brand new. Oil still looks fine at the correct level. All 4 plugs look great. I'm thinking it might be the coil pack, cps, knoc, map, or ect sensors. I'm gonna hook up the yds next weekend. I bought this ski to replace the mr1 in my boat with bad compression and oil/water milkshake. My wife's gonna be pissed if we have 2 bad mr1s! Any tips or advice is appreciated. I have parts to swap from my 04 ar230 engines, but recommendations on where to start will be helpful.
 
Change the spark plugs anyways, it is a cheap fix if it does work.
 
do you have a YDS ? would that show a non firing cylinder in one of the data points?
 
do you have a YDS ? would that show a non firing cylinder in one of the data points?
Another thing could be a misfiring or non firing fuel injector
 
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