Boat not running at full power

[Carolineduff93]

Me and my husband bought a boat yesterday. We took it out today for a first ride. The first hard run we did it seemed to run fine getting up to speed (33 mph) then we stopped and let our kids swim a few mins and when we got back in we noticed a lot of vibration and shakiness and the boat seemed to only be running at half power. When it was full open throttle it was only going maybe 10 mph. Very slow with a lot of vibration and shaking. We decided to immediately trailer the boat until we can figure out what's wrong. My husband said just guessing he thinks it could be spark plugs or throttle cable may not be working properly. But that's his best guess. I'll attach a photo of the motor. If anyone has any ideas of what could be causing this issue please tell me bc we're wanting to try to fix it asap. We don't even know what kind of spark plugs to get.

 

[alldodge]

Right now its anyone guess. Start with removing the plugs to see if any are wet. If water is found then may have blow a head gasket.

See if a plug wire came off, and the distributor cap and rotor look good

New to you boat, was the raw water impeller changed?
Did you notice what the Temp gauge was showing?

 

[tpenfield]

+1 ^^^ There are so many things that it could be, you really need to narrow it down. Are you or you husband any good at mechanical stuff, engines, etc? If not it could be an extremely difficult process to take on your own.

 

[Scott06]

Me and my husband bought a boat yesterday. We took it out today for a first ride. The first hard run we did it seemed to run fine getting up to speed (33 mph) then we stopped and let our kids swim a few mins and when we got back in we noticed a lot of vibration and shakiness and the boat seemed to only be running at half power. When it was full open throttle it was only going maybe 10 mph. Very slow with a lot of vibration and shaking. We decided to immediately trailer the boat until we can figure out what's wrong. My husband said just guessing he thinks it could be spark plugs or throttle cable may not be working properly. But that's his best guess. I'll attach a photo of the motor. If anyone has any ideas of what could be causing this issue please tell me bc we're wanting to try to fix it asap. We don't even know what kind of spark plugs to get.

When at full throttle and only going ten mph were the engine rpms up and the speed not consistent with the rpms engine is moving?
did you check the prop for weeds? If rpm was high could be a slipping prop hub or coupler.
Would look for obvious things like spark plug wire coming off , if you have the skills take off the fuel filter and look at contents for anything other than clean gas ( no water or debris)

 

[QBhoy]

Have you possibly hit bottom ? One of many many issues it could be. Bad fuel is another common issue these days.