Outboard Not Running at Full Power | Boat Slow at Full Throttle | Boat Won’t Accelerate | Boats.net

Why is your outboard not reaching top speed?

We’ll guide you through the basics of what you need to check in the engine, and then we’ll show you what you need to look at on the propulsion side of your boat. Damage to the prop, obstruction of the prop’s rotation, or even the wrong size and pitch prop can impact the boat’s overall performance.

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[artlife]

Heres my number one discovery for loss of full RPM and that is usually fuel starvation, or a pinhole leak in a fuel line weakening the prime. Check for a flattened bulb in case theres an obstruction or faulty check valve. Other things you mentioned are things that dont happen unless someone has changed something.

[jeremysmith]

I have a 200 Yamaha HPDI. When I got it I was getting 63 mph. Now I’m getting 50 mph. Used to it would jump on pad. Now it takes a while. Every ones in a while I’ll take off and it will get back to 63 and I’ll be excited. Go to move from my first spot and it will do it again slow to take off.

[staceymiller]

Bought a 1980 sun runner 17’ ski boat. I’m looking to increase, improve, adapt it for better results.

[donnyhyde]

Failed to include most reasons for failure to achieve speed.

[cichfish]

Just boat a boat with a Yamaha 2 stroke 70 HP (came only being able to go quarter throttle which I knew) just trying to fix it hopefully this helps.

Spark plugs have a ton of carbon build up, maybe this is why?

Installing new fuel pump as well.

[GrummanCheetahPilot]

Like everyone else - I'm here because I cant get issue resolved. 2019 Harris Sunnier with Mercury 200HP Outboard. Purchased used last year and when we took possession of the boat it ran like a top hitting speeds of 50mph with 4-5 people on board. This season it was running rough and not going over 33mph (5000rpm) so I changed the plugs which fixed the rough running, but the boat still wont go over 33mph. If I try to trim it up even slightly it starts cavitation, so i keep it trimmed all the way down. I did change the prop hum assy this weekend to see if that fixed it and to no avail the issue still persists. NO water in the toons, cavitation if trimmed slightly, engine runs smoothly. I'm at a loss here

[MrMoosekiller]

Think you got the pitch backwards lower pitch give you more wholeshot and acceleration with less top end higher pitch gives you slower acceleration and more speed on top end

[myparadiseonbantayanisland]

Had the problem with my yamaha 8hp 2 stroke of not running more than about half speed only 3, 000 to 4, 000 rpm in water barrel in forward gear.
Changed spark plugs and cleaned carb and now it hits 6250 in gear and in water barrel.

[TimsWorkshopTJY]

Cool channel, I've been working on outboards but mainly vintage and the newest a 96 60hp with CDI. I was just asked to look at a 140hp Honda EFI. The issue is it won't start? I've read up on it so I can do a basic troubleshoot but if you have any suggestions or any of your viewers I'd appreciate it. Thanks

[losbrothers]

Hello, I have a 75hp Johnson engine and out of the water it accelerates excellently but when I put it in the sea it does not accelerate almost at all, it goes very slowly, I have already installed new spark plugs and a new fuel tank and hoses.

[bjoejohnson]

Hi John, my boat will only run at 8mph when first starting. After trolling for an hour or so it will run at normal speeds. Please help me I am at a loss for where to go to fix this problem. Thanks, Brad.

[vugprzc]

I have replaced the fuel line Assy and haven't had a chance to check to see if that's the problem yet

[demamatzy]

I need to know some idea to fixed carbrate speed

[tonylaferrera]

I have an older 85hp Force on 17ft ski boat.
It has been running like a top until one day it became hard starting on slow (not even plaining) at top end.
Had it overhauled (fuel, filters, plugs, etc.) and it now starts righf up but still no power.
Mechanic said it was an ignition system (firing order) problem and not worth fixing.
Cant understand how it was fine one minute and now no power.
Any suggestions?

[dang]

My 18ft has a Yamaha 115 on it. I can’t get past about 8.5mph at full throttle. I should be going in the very least 40 mph. Checked gas lines and changed fuel filter.

[tonysimons]

How can I check my IAC valve on my 06 25hp efi 4stroke mercury to make sure it’s bad before spending the money on a new one?

[edmenng]

I have a Mecury 4 stroke 60HP seapro outboard, Just 20hrs . I find that some time the speed at around 5000rpm will decrease to around 4200-4500rpm.and then back to 5000rpm again without change the throttle. Do you any suggestions can give me?

[SABRECRAFT]

higher pitch means higher top speed and lower hole shot

[Robertsjr]

1997 30 hp johnson outboard will run top speed full throttle then just looses power, after about 10 mins. and then bog down and will only go a couple miles an hour at full throttle. already cleaned carb and new fuel lines. Im lost, any ideas

[francischeung]

My 2014 made Mercury 30HP 4 strokes EFI motor stayed at 3000rpm at full throttle, I then changed the impeller, sparks plug, motor oil, gear oil, gasoline filters, and thermostat. After the change, it only stays at 3200rpm. Could you please tell what else I should look at and what spare parts should be replaced?
Thanks.
Francis