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Author Topic:   engine shudders, loses power

david in boston posted 07-26-2001 12:46 PM ET (US)
I was out in boston harbor yesterday, by Boston light. On my way back in, as I was throttling up, the engine started to shudder, vibrate and lose power, I pushed the throttle open to full and the engine kicked in and took off like a shot. I stopped and checked the prop. it was clean, so I started out again and the same thing happened again, only this time it was harder to break it out of the shudder. I took the boat in and now wondering what is wrong. Any ideas? it is a 1 year old Tohatsu 70, oil injected. gas lines were fine, vent open. boat is a 72 whaler bass boat 16. thanks David
Bigshot posted 07-26-2001 01:56 PM ET (US)
start with plugs. If not thensome other fuel related issue. Shuttering is usually 2 of 3 cyls are firing. Coils or CDI's etc, do not clear out.
buster1389 posted 07-26-2001 02:27 PM ET (US)
I had the same thing happen to me with my 1991 18hp nissan years back. I think that the ignition system got moisture in it. I let it sit for a day and it has bee fine since.
david in boston posted 07-27-2001 10:15 AM ET (US)
Thanks for your help, I changed the plugs and will let the engine dry out in the sun today with the cover off. where is the ignition system located? Should I spray with WD40? David
Whaletosh posted 07-27-2001 10:29 AM ET (US)
I wouldn't spray with WD-40, yet. As many people on this forum know I make my living as an electronics tech. repairing chemical instumentation. One of my standard troublshooting techniques is to not change more than one variable at a time. You have changed two already; changing the plugs, and allowing the motor to thoroughly dry out. Neither of these is drastic, nor is spaying with WD-40. but, you goal is to isolate the problem, changing a lot of variables at once con't allow you to pinpoint the problem.
Sean
andygere posted 07-27-2001 12:39 PM ET (US)
I had the same problem. It was a loose spark plug. Cheap and easy fix, esp. since I had feared the worst.
Kim posted 07-29-2001 12:05 PM ET (US)
some times you can see a bad plug wire, if you run it a night ( or flushing it at night ) plug wires will spark easy to see ! in the dark . move them a little, might be worth a try.
kim.

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Author	Topic: engine shudders, loses power
david in boston	posted 07-26-2001 12:46 PM ET (US) I was out in boston harbor yesterday, by Boston light. On my way back in, as I was throttling up, the engine started to shudder, vibrate and lose power, I pushed the throttle open to full and the engine kicked in and took off like a shot. I stopped and checked the prop. it was clean, so I started out again and the same thing happened again, only this time it was harder to break it out of the shudder. I took the boat in and now wondering what is wrong. Any ideas? it is a 1 year old Tohatsu 70, oil injected. gas lines were fine, vent open. boat is a 72 whaler bass boat 16. thanks David
Bigshot	posted 07-26-2001 01:56 PM ET (US) start with plugs. If not thensome other fuel related issue. Shuttering is usually 2 of 3 cyls are firing. Coils or CDI's etc, do not clear out.
buster1389	posted 07-26-2001 02:27 PM ET (US) I had the same thing happen to me with my 1991 18hp nissan years back. I think that the ignition system got moisture in it. I let it sit for a day and it has bee fine since.
david in boston	posted 07-27-2001 10:15 AM ET (US) Thanks for your help, I changed the plugs and will let the engine dry out in the sun today with the cover off. where is the ignition system located? Should I spray with WD40? David
Whaletosh	posted 07-27-2001 10:29 AM ET (US) I wouldn't spray with WD-40, yet. As many people on this forum know I make my living as an electronics tech. repairing chemical instumentation. One of my standard troublshooting techniques is to not change more than one variable at a time. You have changed two already; changing the plugs, and allowing the motor to thoroughly dry out. Neither of these is drastic, nor is spaying with WD-40. but, you goal is to isolate the problem, changing a lot of variables at once con't allow you to pinpoint the problem. Sean
andygere	posted 07-27-2001 12:39 PM ET (US) I had the same problem. It was a loose spark plug. Cheap and easy fix, esp. since I had feared the worst.
Kim	posted 07-29-2001 12:05 PM ET (US) some times you can see a bad plug wire, if you run it a night ( or flushing it at night ) plug wires will spark easy to see ! in the dark . move them a little, might be worth a try. kim.