trolling for hours then oil pressure alarm goes off

[newtoboat101]

1988 thompson 240 hardtop 5.7l vortec /alpha 1 gen 1 ,mercury 9.9 kicker motor ,ok heres what happened, while trolling for 3 plus hours using main motor in gear and about 900-1000 rpm temp normal, and using the kicker motor to dial in the speed, suddenly low oil pressure alarm/horn goes off ,my reaction was to turn the ignition key off ,with the kicker motor noise ,i am not sure if motor had stalled and i did not notice and thats why low oil pressure alarm come on (low oil pressure alarm will sound if engine is not running and key is turned on about 10 to 12 seconds after you turn key to on ,if motor is not running ,or low pressure is detected ) so i pulled all my fishing gear in and started back to home port on my kicker motor half way home started main motor up it fired right up ,and oil pressure was fine from there ,but a new problem came up where i would start out slow ,got up to 10 mph ,but when i would throttle up more around 2500 rpm ,i would lose speed and it would rev rpm's up to 3000 but lack of power , took prop of and did not see any issues ,but i am going to replace flo torx2 parts ,going to do compression test ,and will be checking engine coupler , am i missing anything to check ,by turning key off while loud horn is blowing and kicker motor noise , i do not know if motor had stalled or if it was a true low pressure issue ,motor did start back up ,oil level fine, and oil pressure semms normal any help or suggestion appreciated

 

[alldodge]

Would do same with alarm going off
Need to find out what actually happened.

Start back up and oil press is good so that's not the issue.

If you have an alpha drive, motor won't go above 2500 and could be coupler gave up, and you started overheating

 

[newtoboat101]

thank you for your input alldodge , I also like to state that i have sei 106 alpha 1 gen 1 outdrive ,that being said has anyone had issues with the sei outdrive getting to hot and having populsion issues, ,maybe overheating outdrive ,which i don't have a gauge to know that temp ,i don't know just guessing right now ,ok alldodge so you think engine is fine,started up and oil pressure was normal ,also started and let idle for 5 minutes back in slip oil pressure was fine so skip the compression test ,and concentrate on coupler or flo torx for prop ,maybe thats stripping

 

[alldodge]

Don't have enough info to determine what happened. The sei is same as alpha and thanks for clarifying

If the couple is what gave up, then the water pump stopped turning so it was overheat issue. Being unable to get above 10 mph it lost thrust. Don't see the over heating causing the problem and don't think it's the problem right now. I would pull drive and check coupler

 

[Scott06]

Don't have enough info to determine what happened. The sei is same as alpha and thanks for clarifying

If the couple is what gave up, then the water pump stopped turning so it was overheat issue. Being unable to get above 10 mph it lost thrust. Don't see the over heating causing the problem and don't think it's the problem right now. I would pull drive and check coupler

Agreed wonder if he hit something in water or coupler gave up the ghost as the back and forth of trolling can be tougher on splines.

Would think oil alarm is a red herring and engine stalled for some reason hence oil pressure alarm with ignition still on.

 

[airshot]

Great example of why a kicker motor is better for trolling. Long slow periods of running the big motor typically causes issues down the road.

 

[newtoboat101]

boat is in slip ,gonna switch out the prop hub ,now is there a way to check the coupler while in a slip ,or can i take out on lake and try ,will this coupler totally give up or can i limp it back into slip when i go up to boat this weekend what should i check ,is there a way to mark the coupler to see if there movement

 

[alldodge]

Change prop hub. Don't go far, take boat out and throttle up. If coupler is stripped motor will rev up but boat will not increase speed