MerCruiser 5.0L 220HP Alpha 1 performance (Maxum 2400 SR3)

[CincyMaxum]

Hello,

I bought a new 2005 Maxum 2400 SR3 (overstock) last August which has a MerCruiser 5.0L 220HP Alpha 1 engine. In recent weeks, the engine's performance (RPM and MPH) has slipped considerably. Per the Mercury owner's manual, the engine is rated with a max rpm range of 4400-4800 however presently. I can't get it to exceed 3600 rpm and 35 mph. The boat is rated with an occupancy weight of 1800 lbs (11 people) however I generally don't have more than 1200 lbs and the weight is usually evenly distributed.

I took it back to the dealer last week as its still under warranty however they couldn't find anything wrong with the engine. While the dealer had it, I had them perform the 100 hour maintenance servicing and they replaced the spark plugs but this had no effect on improving the performance. They also performed a pressure check on the cylinders and all were in the 190 range (should be 200 per the dealer) with the exception of one which was 180.

If anyone has had a similar performance problem with this engine on a 2400SR3 and has any insight or advice they could pass along, I would greatly appreciate it. For those who own this year/make/model, what is the maximum mph that you've been able to consistently achieve?

Many Thanks!

[seapuppy]

I used to own it's sister boat from bayliner..same engine/drive combo...I hit 42mph when I first got it...but it was hard to get up on plane...
with that much weight on the boat...your probably lucky to get on plane with the engine drive you have....the boat weighs in at about 5k lbs....plus gear and people...food...water...gas and your rapidly approaching 6500 lbs....now get that stuff moving and on top of the water is going to be a hard task to say the least....the one question I have to ask is was it in the water most of the time???..meaning is the bottom clean??...do you use your tabs to help get on plane??...is the prop slipping???..if your hub is not gripping on the prop..it will slip.....is the flame arrestor clean??.....how much crap do you have on board....all that weight with gear...crab pots...fishing gear...extra first mate all takes power to lift off the water.....put the boat on a diet...you'd be surprised at what you don't use onboard.......and if you don't use it...take it off....
on the engine side...how is the timing on the engine doing???are you getting TAT??....that can slow you down....when was the last time you replaced the fuel filters..???...if they are clogged...the engine won't turn fast enough....
since I'm not anywhere near you and don't know where you boat...I'm only guessing....


SP

[LRose]

I own this boat too. 2006 2400 sc3 5.7 Carb. 250 HP alpha one. The stock prop was a 21 pitch 3 blade. Could not hit max RPMs only 4100 rpm. Did not do well for what we use the boat for, mainly water sports. Took forever to get on plane and hit 44 mph. New prop. 19 pitch 5 blade Mercury High Five. Noticable hole shot, can hear the engine growl now not lug like before and better top end 48 mph (used GPS).