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catcando

Max RPM for Magnum Skier

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catcando

I had some issues with my '95 sporster. Last season I lost my top end. Basically the boat would bog past 3/4 throttle. Did all the basic maintenance and now have swapped the fuel pump out. The boat seems to run well, but I feel that the R's aren't were they should be at full throttle. I'm holding 4200 at full throttle with the stock 13x13 prop. I could have sworn it should be running 4400-4600. My speedos are off so I'm not really sure where my speed is at either. I tried to radar gun the boat last night, with poor results .... DEAD BATTERY!

Any info on rpm out there?

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99response

Carburetor? If so time for some adjustments or a rebuild by a good mechanic.

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EZSnow

How many hours are on the boat? What's the condition of the prop?

Aren't flightcrafts outboards?

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99response

The flightcraft sportsters were inboards with the flighty hull...

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catcando

You got it... 1995 Flightcraft Sportster - INBOARD

Boat has 740+/- hours. This is a Fuelie, TBI.

Boat starts and idles great. Revs without load great, sounds good. Initially this season and end of last year, the boat would not run WFO. It would bog at 3/4 throttle+ and fall on it's face, pull the throttle back to 3/4- it would run great. This year, issue became worse. Running rough under load, and great with no load. I did the basics, plugs, wires, cap, rotor. At this point I do not want to just throw money at it. Brough tto a mechanic. He replaced 1 of 2 fuel pumps. Boat runs MUCH better. Last nigh I beat on it a little and the boat would pull good and run fine at all throttle positions. It seemed like it did lose some combustion on top end. My Tach reads 4200, I thought I remember it being a few hundred higher.

Prop condition is OK, not great, but not trashed, pitted or bent.

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99response

Try and get some fuel pressure readings at speed, you mechanic should have one you can borrow.

Sounds like there is a fuel flow issue. It may be time to replace your injector screens.

-Chris

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catcando

The mech did a pressure reading, although I'm not sure the pressure. I'll have to look into the injector screens.

So anyone know what the max running RPM is? 4500? 4600?

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HDMan16

I own a 95 Response w/ 350 Magnum EFI like yours. I had similar problems w/ the engine surging and bogging and falling on it's face at high rpm's. I replaced all electrical items as you did w/ no good results. I also replaced the mechanical fuel pump and checked the fuel tank etc. All items still did not fix the problem. I subscribed to Seloc online and after some research, I decided to investigate the vapor seperator tank which has an electric fuel pump w/ screen in the tank. My boat has over 1300 hours on it and the tank has never been opened. The screen on the electric fuel pump was very dirty and the bottom of the tank was also dirty. I cleaned both, put everything back together and it has been running perfect since then. I did much research on this site and nobody seemed to solve this problem. If the screen is dirty on the electric fuel pump, it will cause the bog. I have not checked the max rpm's but the boat will go about 43-44 mph and runs like new. Hope this helps.

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footnlongline

I have a 95 350 mag EFI/MP. WOT should be between 4600 and 5000. You should be able to get in this range if your prop is decent and your not overloaded as the FCS is small, light and nimble. I have a SSLX and it came with a Dymex 13/13. It would only do 4400 rpm with that prop so I switched to a O.J. 13/13 4 blade and now I run 4900rpm WOT when temps are under 95. Check for air restrictions, etc.

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catcando

HD,

We're running down the same path. Replaced the mechanical fuel pump and boat runs better, but not were the r's should be I'll follow through on the suggestions thanks!

F-n-L,

Thanks for the rpm range. Did just the prop change alter your runing rpm that much? Was the previous prop damaged? Mine is not damaged per say but may not be 100% true.

As a follow up, I managed to find the owners manual for the mercruiser last night. After blowing the dust off it stated:

Governed @ 4900 rpms (point at which fuel is cut off)

Recommended RPM operating range 4400-4800rpm

I'll go back and take another look to see if any restrictions can be found in air or fuel. With that said, 99 mentioned cleaning injector screens. Anyone know where I can find a parts break down showing how to remove the injectors and inspect?

Thanks for the responses!

Edited by catcando

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footnlongline
HD,

We're running down the same path. Replaced the mechanical fuel pump and boat runs better, but not were the r's should be I'll follow through on the suggestions thanks!

F-n-L,

Thanks for the rpm range. Did just the prop change alter your runing rpm that much? Was the previous prop damaged? Mine is not damaged per say but may not be 100% true.

As a follow up, I managed to find the owners manual for the mercruiser last night. After blowing the dust off it stated:

Governed @ 4900 rpms (point at which fuel is cut off)

Recommended RPM operating range 4400-4800rpm

I'll go back and take another look to see if any restrictions can be found in air or fuel. With that said, 99 mentioned cleaning injector screens. Anyone know where I can find a parts break down showing how to remove the injectors and inspect?

Thanks for the responses!

Although many experts said it wouldn't, the prop change indeed altered it that much. The 3 blade was new BTW.

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vshockey10

Does any one have photos of any of this by chance? we are having a similar situation on our 95 response w a 5.7 TBI 

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JasonK

I'll second the 4400-4800 max rpm for Carb'd 265hp Mercruiser Blue water ski engine.

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