Volvo GXI questions and Issues

[nards444]

I got a 2002 Chaparral 265SSi with the 5.7GXI 320hp with Volvo duo prop, 230hrs on the boat. Got the boat last year took it out once engine sounded good but could only get the boat up to 4000rpm and roughly 38mph. So I chalked it up to bottom paint needing a redo(which still needs to be done) and propping. Boat was propped with F4s, I called a dealer they said my boat needed F6s. So I did the swap.

Fast forward to this summer, did the new props. Get out on the water, I picked up 200 rpms, but no real speed. And have also noticed intermittent starting issue, where I will have to give it throttle to get started and once I came off plane quick and it died. But boat does seem to idle alright.


I called the dealer I bought it through they told me boat had new risers gaskets, plugs wire and rotor and cap put on, also a new fuel pump. Verified the plugs were new, the cap and rotor looked new, wires weren't, they didn't look bad, but I replaced them anyways. Also this spring it had new oil, filter, fuel filter put in. Also replaced the thermostat and impeller. Boat operates around 150 degrees.


This GXI engine should run at least 4500 rpm at WOT, but Ive read where the GXI should go to 5000 or 5500RPM. can anybody verify this?


Anyways closest dealer is over and hour away, summer is in full swing, and the boat does work, so I don't want to go that route. I also don't want to keep throwing parts at . Just wondering if there are anymore ideas.

 

[nards444]

this is the cap. They said it was new. if it is its been ran 3 times maybe with 10hrs. there seems to be some white on the prongs. don't know if this is normal

 

[Dave-R]

I have the same engine and outdrive as you. Mine is on a Cobalt 226 and is very responsive . Our altitude varies from 4000-6000 ft. Top speed = app.50 at 4800 rpm. Your boat is a very heavy boat, and will need a lot of power to get you to the mid 40's. I think you need to prop down to get your engine at WOT to about 4800-5000 where the engine makes the most power. I would see if your dealer could let you try a different prop set. I think I have a F6 set but am not sure. Your boat should have been ordered with a big block if you are looking for more performance. Dave-R

 

[nards444]

thanks. I have already changed props. It was used a boat I had not option for a bigger engine. The boat came with F4s, the proper prop is F6s which it is, which did net me another 200 rpm, so propping down would not help.

Still doesn't explain the loss of 600-1000rpm. As heavy as the boat is it still should get 4500 rpm min and 45mph.

 

[Dave-R]

I checked, and my props are F5s. Maybe I have it wrong, but I think you should have propped down from the original F4 you had to an F2. We need to know what your WOT rpms are now with the F6 set you have with a heavy load. Should be around 4800+. If you are not propped right, the boat will be a dog. The engine can be damaged by lugging it , and if it can reach recommended WOT with a load that will prevent that also. Dave-R

 

[nards444]

in Volvo props the higher you go the higher pitch, thus F6 is higher pitch than an F4. With F4 props I was getting around max 4k rpm at wot I can now get 4200. Propping down usually nets lower RPM, lower top speed but better out the of the whole, propping up does the opposite.

Props are not the issue, as going up got me more RPM, going down in prop would only net me less RPM and less speed. Issue has to be air, fuel, spark. Air should not be a problem, plugs, wire,s cap and rotor are new, batteries and connections are fine. That leaves me with fuel or something in the ECU that is limiting the engine.

But I agree I should be in the 4500-5k range at watt, as it sits im probably at least 500rpm short.

 

[Senior B]

I must say that you're in error on your prop statement. The Lower number is a lower pitched prop set which will increase hole shot, Raise WOT RPM but lower top end speed. Now the fact that you gained RPM could be from a number of things like maybe your F4 set was damaged but that GXI motor should be able to spin up to @ 5000 RPM at WOT. Now that being said, I believe your boat was offered with a 8.1L 496 Big Block that would spin a F6 propset but that big a craft with the 5.7 probably came stock with the F4 set. If it were me, I would have the F4 set looked at by a prop shop. I would also look at the Outdrive Gear Ratio which I believe should be in the 1.97 range for a boat of that size and weight with the 5.7L. Now as for bottom paint, Bottom paint will slow you down some like 2-3MPH over no bottom paint. A dirty bottom with a bit of growth will slow you down a lot. Good Luck and god speed.

 

[nards444]

Yes i mixed up the RPM. But the whole shot and speed i was right as you said. When I bought the boat used it came with F4s, got rid of them and got the F6s as thats what the dealer said came with it. It has netted me some better RPM, marginally but no real speed.

Either way. I dont think propping is the issue. As Im still missing 800-1000RPM. Bottom paint has no growth but does need to be redone.


So far I have tackled the cap rotor, plugs wires, new fluids and filters. I think the problem lies in the fuel system, which I have ordered a gauge to check it, which would leave me with a bad pump, anti, syphon valve, bad fuel pressure regulator, or bad/dirty injectors.


I bought the boat last fall ran once only getting 4000 rpm tops, so the issue was there before I got it. I did put stabil in last fall, but another possible issue is it may just have some bad gas in it and needs to be ran clean. Ive only been out twice this year due to weather, but have put some gas in it ethanol free.


Overall the boat sounds good, and doesnt seem to bog, i just think its not getting enough or the wrong fuel somehow.

 

[nards444]

Just an update. Tore off the fuel pressure regulator, the screen was clogged, figured it was 12 years old so id replace the regulator. Also replaced the anti syphon valve and check the gas tank vent.

Took apart the pump, on the bottom two screens they were not clogged.

Put all back together ran the boat fired right up, but it always has. Hooked pressure gauge up to it, and got 18-20 on the low side, 52 on the high. So something is wrong with the low side. Connections are all tight no fuel leaks. Also replaced the fuel filter that was new this spring to eliminate it.


kind of thinking the pump may just be shot. when I reved it up then came down quickly it did die.

 

[nards444]

At a loss replaced fuel pump. Still getting 18 on the low side and after revving high boat stalls. Noticed the pump canister farthest out or the wires sticking out of it, the fuel line goinf in the print is missing g. I'm not getting a leak there. But maybe it's drawing air.

Fuel tank vent clear. Syphon valve replaced. High side fuel pressure is on at 52.

Leads me to beleve it's at the pump or before.


After the install of a pump should I habe bled the air somehow

 

[Thalasso]

Nothing wrong with the pump if your getting 18psi

 

[nards444]

see I thought the low side was supposed to be 8 plus or minus 4?
Ive now replaced the pump, cap rotor, plugs, wires. Still getting hard starts after being hot, and coming off of plane quick will die. Dont know where that leads me.

 

[Flow9181]

see I thought the low side was supposed to be 8 plus or minus 4?
Ive now replaced the pump, cap rotor, plugs, wires. Still getting hard starts after being hot, and coming off of plane quick will die. Dont know where that leads me.

I know this thread is 5 years old but did you ever solve this issue ? My boat does the same thing.. I'm thinking it's to much boat for the motor they put in it