Boat doesn't want to plane out

[monster1]

Sorry if this is in the wrong section. I took the boat out for the first time in months yesterday. I topped off the fuel tank last season but forgot to add fuel stabilizer. It starts and runs fine, but I've noticed considerable lack of power when trying to get up in plane.

The boat just struggles to get out of the hole. The bow goes up in the air and the engine won't go above 3000 rpm's. The boat is loaded just as it would be for a full on overnight trip weight wise. I lighted the load in the stern bringing some weight forward. This allowed the boat to just barely get up on plane.

Once on plane, the engine was running at 4400 rpm and 38 miles per hour. I'm thinking the fuel has lost its octane level since I forgot to stabilize the fuel before fill up last fall. But I didn't have this issue months ago when I ran the boat last.

The engine is a volvo 4.3gxi. It's in good repair and runs good. I haven't changed the plugs or crab distributor cap out in several years. It was still running good so I figured why waste money on those things if the engine is running good? Was I wrong? Everything else is kept up. Thoughts?

 

[hemitom]

i would try and run most of the tank of gas out ,fill with fresh gas and a can of berrymens b12 first.
Also is the trim working properly ?

 

[TeamZero]

Poor fuel....even with stab. my 270 Rinker was always lazy until I ran a fresh tank through it.

 

[Strokenmerc]

Check your fuel filter, fuel lines, and water separator if equipped. I had a similar issue with an outboard that was fixed by replacing the fuels lines. My old lines were collapsing under high load restricting the fuel supply. No issues idling and low loads.

 

[Whipcitywrencher]

Yep, probably the fuel, run it to almost a 1/2 tank or sooner and fill it with some good stuff.

 

[Driz]

Id try to siphon off if possible a good portion of that old gas and fill it with fresh. Filter check naturally .and don't forget these likely a tiny one up on the carb body inlet the often gets forgotten once a spin on gets installed. If you haven't pulled the distributor cap Id do it FIRST just to be sure. Ive had my 4.3 for 22 years and that baby will grow fur on those contacts like you wouldn't believe. Mine lives in a barn all year too so it must be just lack of use and storage that grows it. I change my cap every 5 years or so because of that but clean it every year or so with steel wool or a tiny brush on my Dremel tool. While its off check the rotor and clean too. Under that there's the pickup, a tiny stainless thing down under the rotor. If its rusty looking clean it up because when it gets just so funky it will decide to stop right there.
Check your choke butterfly that its free and moves open as the engine warms up. Ethanol has a nasty way of fusing those things on so it runs rich. I had that happen too. I doubt that it would kill your power past 3K though.
Another long shot, how old are your fuel lines? Are they alcohol rated? If they don't say it on them replace them now . The inside liner on the old sort of fuel lines will break down depositing black goo into your carb. According to my buddy the boat wrench it goes straight through any sort of filter. It was common in the early days of the Ethanol Curse.
Its probably old gas from what you describe though. If a fresh tank of gas doesn't do it there is one other thing that happened to me once that made mine do just what you describe. Wallow to 3000 anything more and it started falling off. Startyed and ran perfectly under 3K and with no load on it. Weird. Mine is a 2BBL Mercarb (Rogchester). I ended up pulling the top up off the carb right ih place and digging all the moss, yea moss that was growing in there. Once that was gone it ran fine again for years until I rebuilt a while back,

 

[monster1]

Thanks for the responses. The fuel filter is new, as is the fuel line. The check valve is the original (2004). I'm afraid to change it out because I don't want to chance cracking the plastic gas tank.

I recently refurbished the fuel pump. It's the Carter built pump that gets paint chips in it and fails. I cleaned all components and put it back together. It was running within spec on the last launch. I'll check the fuel pressure again to rule that out.

In fact, I think I can bypass all this troubleshooting by simply running the boat again on a portable tank of fresh fuel. If that's the issue, I have approx 80 gallons of gas to pump out and run in my commuter car and refill the boat with fresh.

 

[Driz]

Do check your tank vent too before getting too far into this. If you can blow some air into it with the cap off and listen for escaping air. Not likely your cause but it could be only be plugged enough to allow it runnin but not under high draw. You might have a tough time finding plastic tubing enough to reach your gas can . I tried to buy some last month and the hardware store owner said his supplier had gone out of business. He said many of them had ...... and he went out recently
I pull the sender unit on mine to do this. It lets me see what’s in there and suck the gunk out that’s accumulated over the years. Disconnect the battery and hand screwdrivers , work outside of course , no sparks yadda yadda.

 

[monster1]

Last year I thought I had water in the fuel so I pulled the sender and pumped out fuel into a Mason jar and let it sit. It never separated and was clean. No crap in the bottom of the tank.

 

[GoldDot40]

New spark plugs will likely fix it. I've worked on more than a few that wanted to run "flat" on open water. They all started good, idled good, and seemed to run good other than lacking power. Spark plugs fixed them every time.

 

[TeamZero]

Thanks for the responses. The fuel filter is new, as is the fuel line. The check valve is the original (2004). I'm afraid to change it out because I don't want to chance cracking the plastic gas tank.

I recently refurbished the fuel pump. It's the Carter built pump that gets paint chips in it and fails. I cleaned all components and put it back together. It was running within spec on the last launch. I'll check the fuel pressure again to rule that out.

In fact, I think I can bypass all this troubleshooting by simply running the boat again on a portable tank of fresh fuel. If that's the issue, I have approx 80 gallons of gas to pump out and run in my commuter car and refill the boat with fresh.

Don't waste any parts on it until u get fresh fuel in it. Id be real careful messing around with another tank....fumes in a boat are a baaaad idea. After 1st year it did it to me, I left tank real low over winter, and filled with fresh in spring....never an issue again. Use a real Volvo filter to, not the aftermarket crap. Must be EFI if it has that pump?GXi should be efi... I took mine apart and cleaned it up to as preventative maint. so didnt have an issue. Keep us posted on outcome

 

[monster1]

Don't waste any parts on it until u get fresh fuel in it. Id be real careful messing around with another tank....fumes in a boat are a baaaad idea. After 1st year it did it to me, I left tank real low over winter, and filled with fresh in spring....never an issue again. Use a real Volvo filter to, not the aftermarket crap. Must be EFI if it has that pump?GXi should be efi... I took mine apart and cleaned it up to as preventative maint. so didnt have an issue. Keep us posted on outcome

Thanks. Yeah, I don't plan on buying parts to chase the issue if I don't know what it is. I can run the boat on a small one gallon tank without endangering myself or others. I'm just planning on running it for test reasons. Not going to be starting out the season with a portable fuel tank on deck. I'm sure it's been done. Lol

 

[monster1]

New spark plugs will likely fix it. I've worked on more than a few that wanted to run "flat" on open water. They all started good, idled good, and seemed to run good other than lacking power. Spark plugs fixed them every time.

Just got a fresh set of autolite platinums in the mail today. After I verify fuel pressure, I'm going to change out the plugs (they need changing anyway) and check the cap and rotor. Ill take it to the lake and run it. If it planes, I know I've found the issue and no need to run it on a portable tank with fresh fuel to see if the tank is full of bad fuel.

 

[GoldDot40]

Good deal. Keep us updated.

 

[nicholas]

After you run or drain the tank - - refill and run two bottle of redline SL-1 in the tank.
That will get your carbs or injectors and combustion system clean as a whistle!!!

 

[monster1]

Stopped by the boat shop today and bought a new anti siphon valve for the tank. I've heard for years these little things can be the culprit of many things. The new one of course is brand new and I can blow though it easily. I pulled the old one off and blew through it and it has noticeable restriction compared to the new one. There was a little corrosion as well, but not bad. I hope this was the issue.

I'll still change out the plugs, cap, rotor and possibly pull the injectors or at least clean them on the full rail. I'll recheck the fuel pump numbers to make sure it's within spec and take it to the lake to run it. I'll keep everyone advised.

 

[monster1]

Changed out the plugs this morning. They were all clean except for #4 and # 6. Half the insulator was covered in varnish on each. Plugs are about 5 years old.

 

[SeaJay]

Check the bilge to ensure no water taken on over the winter. Also check the prop for inadvertent damage over the winter. If those are both okay and the boat planed last season then there is something not working properly on the engine. Could the engine be going into limp mode for some reason is another thing to consider.

Good luck in getting to the bottom of this problem.

 

[monster1]

Seajay,

To answer all your questions, no. I'm certain it's probably the combination of the things I've found that needed attention. But probably mostly the anti siphon valve. Those things are really problematic from everything I've read. I'm usually a "don't fix it if it ain't broke" kinda guy, but I'm beginning to think that doesn't really apply to routine maintenance, especially when ethanol fuel is evolved.

 

[monster1]

Just got back from running it at the lake. New cap and rotor. New plugs and New anti siphon valve. Boat hops right up on plane now loaded like it was when it wouldn't plane last week. I'm sure the new cap and rotor and plugs helped out, but I'm convinced it was the anti siphon valve. At least it wasn't the fuel being the issue. That would have got expensive to just dump and replace. Oh yeah. Lost my spare tire somehow on the way, so it's not a complete victory.