50 hp Yamaha 4 stroke bogs down

[mamrhein]

I have an '02 Yamaha 4 stroke with 320 hours on it. It starts, idles and runs fine. After being at close to full throttle for 10 minutes it suddenly bogs down. I immediately go to neutral and can hear a significant valve tap. Like a car with no oil. After idling for a minute or so the tap goes away. Boat will get right back up on plane but will eventually bog down again. I just put a new impeller in cause i thought it may be overheating. Could it be related to a faulty oil pump? The noticeable valve tap has me thinking that.
Thanks, Mike

 

[99yam40]

Re: 50 hp Yamaha 4 stroke bogs down

Does your alarm system work?
May need to have it all tested.
Being 4 stroke it probably has low oil pressure switch also and you need to find out if that alarm works as that might be what is coming in.
Have you changed oil lately and is it being thinned out with fuel(making oil)

 

[mamrhein]

Re: 50 hp Yamaha 4 stroke bogs down

Does your alarm system work?
May need to have it all tested.
Being 4 stroke it probably has low oil pressure switch also and you need to find out if that alarm works as that might be what is coming in.
Have you changed oil lately and is it being thinned out with fuel(making oil)

Capt.
Thanks for the reply. I changed oil toward end of last year. I used Yamalube that I got from dealer. Do you know how I can test the low oil pressure switch, or entire alarm system? I don't get any beeps, tones or alarms when I go to start it as some engines do. Should I? If fuel were mixing with oil, wouldn't level rise on dipstick? After checking it, it seems a little thin. Doesn't smell of gas though. I will change it before next trip. That low oil pressure switch really sounds like a good culprit based on my symptoms.
Mike