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951 / 947 Break In
- Thread starter amcreativ
- Start date
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New plugs in (NGK BR8ES Solid), airbox is finally properly secured. I still haven't been able to attack the tuned pipe. I also gapped and put in a new set of spark plugs. I would say that the hesitation and bogging both have been a bit less, but they are still there. However, I took some quick videos of how the ski is acting and what it sounds like.
Hesitation Video - This clip shows what happens but randomly. More often it's from idle that it occurs. Sometimes it shoots right out of the gate like it should and no issues on the top end. Sometimes it bogs down, sometimes it hesitates. Less today than yesterday that's for sure.
Idle Hang - This next clip shows an issue I've been having since I brought the idle up from 1300 to 1500 in the water with a warm motor. The revs now hang up around 2100 for 5 seconds sometimes even up to 10-15 seconds before they drop to 1500. I find putting load on it, like taking it from N to F, will make it go up a bit higher. I also noticed the slightest touch to the throttle can bring the RPM's up, like THE slightest touch. Throttle cable too tight? The ski also wants to run 4000 RPM or higher out of the water. The old motor would sit nicely at 3300 out of the water and never higher unless I pushed the throttle. This one wants to climb and climb. If I leave the idle screw where it was, it is around 1300 in the water, and in the 3000's out of water.
Gurgles - The ski also tends to sound like it's gurgling a lot after I let off the throttle until the RPM's take forever to go back down to idle.
Hesitation Video - This clip shows what happens but randomly. More often it's from idle that it occurs. Sometimes it shoots right out of the gate like it should and no issues on the top end. Sometimes it bogs down, sometimes it hesitates. Less today than yesterday that's for sure.
Idle Hang - This next clip shows an issue I've been having since I brought the idle up from 1300 to 1500 in the water with a warm motor. The revs now hang up around 2100 for 5 seconds sometimes even up to 10-15 seconds before they drop to 1500. I find putting load on it, like taking it from N to F, will make it go up a bit higher. I also noticed the slightest touch to the throttle can bring the RPM's up, like THE slightest touch. Throttle cable too tight? The ski also wants to run 4000 RPM or higher out of the water. The old motor would sit nicely at 3300 out of the water and never higher unless I pushed the throttle. This one wants to climb and climb. If I leave the idle screw where it was, it is around 1300 in the water, and in the 3000's out of water.
Gurgles - The ski also tends to sound like it's gurgling a lot after I let off the throttle until the RPM's take forever to go back down to idle.
jhjesse
Well-Known Member
I have built several of these engines and even more DI 951's. have tried several methods of break in and this is what I like the best.
After everything is corrected and the ski is running good idle out to the no wake buoy then pin it. Ride it like you stole it. It will stay together or come apart. Haven't had one come apart yet. JMHO
After everything is corrected and the ski is running good idle out to the no wake buoy then pin it. Ride it like you stole it. It will stay together or come apart. Haven't had one come apart yet. JMHO
Good news is the low end hesitation is gone, same with the idle hang and run away out of water. Bad news, I have no top end but I had it before. It climbs up to speed a bit slower, gets up there and then just dies out prematurely before hitting top end speed. It will rev all the way up just as you pin it but it won’t sustain it long enough before it dies down to an idle. Not even a bogging, just quits to idle.
So I’m now on straight gas, put a dash of marine stabil 360, 91 no ethanol, low end hesitation seems to be gone, same with top end power and speed.
I did a high speed run, cut the motor and the brand new, 15 minute ram spark plugs look like this.
I like to think it’s okay but possibly borderline lean. Trying to avoid rebuilding the carbs for now but I’m thinking I’ll have to.
I did a high speed run, cut the motor and the brand new, 15 minute ram spark plugs look like this.
I like to think it’s okay but possibly borderline lean. Trying to avoid rebuilding the carbs for now but I’m thinking I’ll have to.
I saw one of your posts mentioning Group K and you spoke highly of their work. I remember them from about 20 years ago, so I sent them a cylinder head and they did a great job!
There is no other shop that I trust, Harry is "The Man" when it comes to skis and always answers the phone.
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