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Charles, Marine Mechanic
Category: Boat
Satisfied Customers: 3936
Experience:  US Navy (Ret) Certified Mercury Marine Tech with over a decade of repair experience.
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I recently purchased a boat with a 98 Suzuki DT 225HP

Customer Question

I recently purchased a boat with a 98 Suzuki DT 225HP motor on it. The first thing I had done was have a 100 hour service on it since it had not been run in over a year. After that took it out to the ICW and it would turn off constantly on idle speed and would not rev up past 2000 RPMs. It would turn right back on and 3 seconds later off...on and off...etc Took it back to mechanic and had the following repairs: Replaced fuel pump regulator, Replaced CDI box, Replaced throttle sensor, Replaced primer bulb. Took the boat out and now will rev up past 2000 RPMs and runs well. Sometimes will still have problems getting up past 2000 RPMS after ideling and recently needle went crazy under load at 4000 RPMS and motor was struggling, lowered the throttle and seemed to do ok under 2000 RPMs but did not want to come back up right away. Almost always motor will pick back up and plane after turning off and on or sitting a while and reving up the motor in neutral. I would greatly appreciate any information as to what could be happening?
Submitted: 2 years ago.
Category: Boat
Expert:  Charles replied 2 years ago.
What it sounds like you have happening is that the motor is loading up when going at low speeds. This could be due to over oiling, poor quality oil, or the injectors are leaking excess fuel into the cylinders.I would remove all 6 injectors and have them cleaned. Reinstall them and give the boat a good run. Make sure that you are using a quality marine oil rated TCWIII. During the sitting the injectors most likely clogged some and this is the cause of the problem.
Customer: replied 2 years ago.
I thought it was something when only going slow but as I mention the last time it happened I was already running at 4000 RPMS for about 20 min when it started struggling to keep going in the middle of the run. The throttle was not touched up to that point and I was on my way out at sea.
Expert:  Charles replied 2 years ago.
Does the alarm work in the boat?
Customer: replied 2 years ago.
I have not heard an alarm, but have read that some others have had problems with the motor thinking it was overheating and by turning off the motor for a bit and turning it back on it would work back as normal. Something about adding an adapter to the purple and white wire solved their issues? Is there a way to test if my alarm works?
Expert:  Charles replied 2 years ago.
Yes, Turn the key on, then take the sender out of the oil tank, the alarm should sound with in a few seconds.
Customer: replied 2 years ago.
Ok. I'll try that and get back to you but it's going to be a while before I can try because I am out of town. So you think it might actually be overheating or just that it thinks it's overheating?
Expert:  Charles replied 2 years ago.
That could be the cause. If you have not serviced the cooling system in some time, it could still be overheating. If the alarm is not working, you just would not know it.
Customer: replied 2 years ago.
Thanks for your help so far. I did service the motor before I even took it out for the first time. It got a 100 hour service. Can you think of anything else that would cause the motor to struggle in the middle of a run like that?
Expert:  Charles replied 2 years ago.
Low fuel pressure, loss of spark, water in the cylinders, excess oil in the system. bad spark plugs.