Help with low rpm's and speed - 2005 Seadoo Sportster 150 4-Tec non-supercharged

[Dlh1228]

Hello,
I was hoping one of the members here may be able to help me with my new boat. I have read many of the prior posts, but could not find an answer to my low rpm/low top speed problem. I have always owned Seadoo PWCs, 95' SP, 97' XP, 2001 XP. I have always tried to do a lot of the maintenance myself, with the exception of major engine work.
I recently purchased a 2005 Sportster 150 with the 4-Tec 150hp non-supercharged model. I took it to my local dealer for a thorough inspection and service since I did not know the history of the boat. Based on the service advisor, it currently has 150 hours, good wear ring, and no nicks/damage to the impeller, no motor issues, no fault codes, etc. I just had a full service with oil change, all new spark plugs, oil filter, check all cables, etc., and was told everything was in excellent condition.
I just took the boat out for the first tome this weekend but was unhappy with the performance. Top speed was only 39 mph (per GPS) at a maximum of 6,100 rpm's. It also took approximately 6-7 seconds to get on plane. This was with 2 people 175lb each, no gear, and a full tank of fresh gas on water that was flat like glass. According to the shop manual the max rpm's should be 7,650 and I understand from reading many of the forum posts from sportster and speedster owners of non-supercharged boats that my top speed should be approximately 50 mph at those rpm's. At this point the dealer says there are no fault codes and does not know what the problem could be. Any ideas? Any help would be greatly appreciated. I was set on buying a non-supercharged unit because I was fine with a top speed of 50mph, but I am not happy at all with 39mph. I hope I don't have to go to a SC model. I really like everything about the boat with the exception of the slow top speed.

 

[n-mod]

Something isn't right. I suggest you pull the spark plugs and make sure they look good. Maybe they didn't replace them. I had very similar symptoms when one of my plugs fowled.

 

[devonte007]

You should get full RPM's and a top speed of at least 45mph in this boat (50 on a perfect day wind at your back).

I realize that it was just fully serviced and checked out but something is definitely not adding up. First a few simple things to check:

1. gas - how old is the gas? Old gas and water in gas can cause performance issues.
2. Impeller - any idea if it has a stock impeller or something aftermarket? If it is pitched too high it can reduce the performance of the engine, especially the N/A version.
3. spark plugs - you mentioned that they were replaced but you may want to get another set and replace them one at a time. Have heard of brand new spark plugs being bad. Does it seem like the engine is missing or just not running on all cylinders at all? These 4-tec engines are hard on spark plugs, especially the SC versions. Also make sure they are gapped correctly to 0.030"
4. oil level - make sure the oil level is exactly right in the middle of the two bends on the dip stick. Too much oil can cause performance issues.
5. DESS lanyard - the lanyards can be programmed as learners key, rental, etc. and can be set to limit engine performance. Might check to make sure your lanyard is programed as a fully operational key.

That is about all I can think of off the top of my head, check back and let us know what you find. If not anything above we'll try to dive deeper.

 

[Coastiejoe]

I will touch on oil level again,, If it is over-full it will decrease the engine RPMs and performance. Even 1/4 inch will affect the performace.

 

[Dlh1228]

Thank you for all the suggestions. I am swamped at work this week, but will try to check those things next weekend. I am going to pull the plugs and check them and check the oil level as suggested and will report back. There was about 5 gallons of 6-8 month old gas in the tank when I purchased the boat last week. I topped off the tank with fresh fuel and added an entire can of Seafoam. Should that have done the trick if the old fuel was bad? I did notice I gained about 100rpms after I ran it for about an hour.
Is there a way I can tell if the impeller I have is the stock impeller? Does anyone know that the stock pitch is? Should the pitch or part number be stamped on the impeller?
I was thinking of pulling the fuel pump and checking the fuel filter. Would this be worth while? Is this a big job? I regularly cleaned the fuel filter on my XP limited, but that fuel filter seemed a lot easier to access.