Guys, have F250's and fish NE canyons.Have noticed that every year have less speed.this year am winding up 5000 rpm and am turning 26-27 knots, last trip to the Hudson was 5100 rpm burning 35 gph. most trips is 4-5 guys,overnite gear, 500-600 lbs ice and alot of chunk bait.what are others burning? should I be looking for a problem like injectors? Blades are perfect, bottom is painted every two years with ablative, thx in advance.
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2006 330 express
- Thread starter Randy
- Start date
Tuna Man
GreatGrady Captain
I have an 06 Marlin with the same engines. Loaded for an overnight canyon run (on the way out) we do about the same speed as you, but only spin at 4400 or thereabouts while burning about 25gph. I know your boat is three feet longer, about a foot wider and much heavier but your numbers don't sound good. Was ther performance much better in the past? I would think you could get 1nmpg most of the time and still be able to do 25-30 knots. My guess is your props are not grabbing the water they used to or your bottom is no where as smooth as it once was.
I know I've written this before, but a relative used to own a 1989 Marlin. With a clean freshly painted bottom (very smooth, just redid it) he was able to spin the engines to 6100rpm while doing 42mph. After the boat sat for a little over a month he went for a ride the engines only spun to about 5200 and the boat would not go over 33mph. Yes this is an extreme case, but the bottom was covered with soft marine growth (looked like 1/4" long baby hair). Keeep it simple, check your bottom for growth first.
I know I've written this before, but a relative used to own a 1989 Marlin. With a clean freshly painted bottom (very smooth, just redid it) he was able to spin the engines to 6100rpm while doing 42mph. After the boat sat for a little over a month he went for a ride the engines only spun to about 5200 and the boat would not go over 33mph. Yes this is an extreme case, but the bottom was covered with soft marine growth (looked like 1/4" long baby hair). Keeep it simple, check your bottom for growth first.
If all other factors are the same such as load, amount of canvas and amount of fuel on board the first thing I would check would be fouling. You say the props are good so we can eliminate that.
If it's not bottom growth you then have to assume your engines are putting out less power at the same rpm. Engines need air, fuel and spark to run. Make sure sure your plugs are clean, the fuel flow is unrestricted and you have good even compression in all your cylinders.
Another factor might be bad fuel. Check all the other issues and then try again with a fresh load of fuel from a vendor that sells lots of fuel so you're not dealing with stale gas.
If it's not bottom growth you then have to assume your engines are putting out less power at the same rpm. Engines need air, fuel and spark to run. Make sure sure your plugs are clean, the fuel flow is unrestricted and you have good even compression in all your cylinders.
Another factor might be bad fuel. Check all the other issues and then try again with a fresh load of fuel from a vendor that sells lots of fuel so you're not dealing with stale gas.
eppem
Well-Known Member
Use startron and ring free always, yard maintained with tune up every year, burn alot of fuel and get gas at jacksons marina which sells alot of fuel. How can I check injectors or is that strictly a mechanic thing?
It can't be the motor, the RPM's are coming up just the boat speed isn't. If it's 1 motor it may be a spun prop but both at the same time is unlikely. If 1 is slipping the other will have to work it's tail off to make up the difference. Is there cavation? Is the fuel burn the same for both? The bottom paint may be fresh but have you checked the bottom?
melkat
GreatGrady Captain
Tashmoo
Well-Known Member
Ask your service guy if fuel pumps could be the issue. In past engines (2 stroke) when I replace the fuel pumps after 1,000 hours it made a big difference.
Had VST cleaned last season, no cavitation, when I hauled out for Irene I checked the bottom and had some slime. powerwashed it. Havent run it since. Going to take it with full fuel and water and run it alone,in the beginning of every season i run it to see if I get 6000 rpm and 34 knots top. will see if i am getting that now without crew and overnite load.