suzuki dt115 high rpm prob.

[maintain-man]

I have a 1988 suzuki dt115 on a 19' vip fiberglass boat. problem I have is, at about 5000 rpm, under w.o.t, the motor will drop to 3000 rpm, runs rough at 3000 until I throttle down. watching my fuel gauge it goes to empty when rpm drops. if I put in neutral for a moment then throttle up again, fuel gauge comes back to 3/4 tank and I am able to continue running up to 5000rpm then does it again. (rpm range is 4800 to 5500 rpm for this motor.) I thought it was overheating so had waterpump replaced. pump needed changing but didnt correct problem. Dont hear or see any alarms when problem occurs. what should I look for, and what may cause motor dropping to safe rpm?

 

[31900]

Re: suzuki dt115 high rpm prob.

The fuel gauge dropping indicated to me that there is 12 volt short somewhere. Look for stripped cables and water in your harness.

 

[fridays]

Re: suzuki dt115 high rpm prob.

Sounds to me like your tach is wrong and your prop too small..you may be hitting the rev limiter. The limiter cuts it back to 3000 and to reset you go to idle then back up..just what you described. fuel guage ????? don't know

 

[maintain-man]

Re: suzuki dt115 high rpm prob.

Originally posted by FridaysMarine:<br /> Sounds to me like your tach is wrong and your prop too small..you may be hitting the rev limiter. The limiter cuts it back to 3000 and to reset you go to idle then back up..just what you described. fuel guage ????? don't know

 

[maintain-man]

Re: suzuki dt115 high rpm prob.

while testing this weekend it seemed to run like it was missing, plug wires on 2 of 4 cylinders seem to be loose. gonna try going up in prop size. prop is a 16 SS turbo. kinda leary listening to guy at marina, he is the one that told me a 16 would work best. said if was wrong size would take prop back but would charge a $30 restock fee. not sure how much to go up in pitch. would the next size 18 be enough? or a 20 to much? I was told for a suzuki they go in even #s

 

[jafa]

Re: suzuki dt115 high rpm prob.

If your running 5000 at the moment it'll be worse if you increase the pitch, your on the low side at the moment. <br />Back to the problem. Normally a motors ignition system and boat electrics are completly isolated from each other. Dropping to 3000 rpm indicates the engine thinks its overspeed why this should affect the tank display (problem or cause) is a mystery. Does the engine run rough for about 10 seconds before the speed drops, any alarms ? If the two are definatly linked then disconnect as much boat electrics as possible and have a run out , I'm guessing a ground problem.

 

[maintain-man]

Re: suzuki dt115 high rpm prob.

put on my 17 alum prop and if I ease into full throttle it gets to 5500 rpm with throttle left but then it will drop back to 3000rpm if I try going wide open. wondering if I am getting prop blowout when trying to go w.o.t all at once. If it starts missing seems like it drops to safe rpm sooner than 5000. I think I have a combination of things not right here

 

[jafa]

Re: suzuki dt115 high rpm prob.

I dont know specifically about your model but on other suzi's the protection circuit will drop pulses when it overspeeds which sounds like a misfire. If you dont pull back within 10 seconds it will auto drop it to 3000 rpm. The only way to get back is to bring it to idle. Wonder if your tach is reading on the low side ? Another thought is that the prop hubs spun at full throttle but as you have changed props thats unlikely. I think overspeed kicks in at 5900 not sure.

 

[maintain-man]

Re: suzuki dt115 high rpm prob.

should primer bulb stay hard all the time? mine isnt. If i disconnect the fuel line before the pump bulb will stay hard. If i disconnect line after pump, bulb will not build pressure