88 DT-200's have no mid range?

[R_Andersen]

I have twin 1988 Suzuki DT-200's and have been having a problem with them ever since I bought this boat 2 years ago. The motors both start and idle perfectly and then run perfectly at cruising speeds over 3000 rpm.<br /><br />The problem is when trying to troll at medium speeds (7-9 kts). During slow trolling the motors will run perfectly anywhere in between 600 and 1800 rpm. 1800 rpm gives me about a 7 kt trolling spped. Then if I try to slightly increase the speed to a little faster what happens is both motors will then jump up to about 3000 rpm or more and the boat comes up on plane. <br /><br />There is no way to get the motors to run between 1800 and 3000 rpm. When I am at 1800 rpm, no matter how slightly I increase the throttles, both motors immediately speed up to over 3000 rpm. They both act exactly the same way when this happens.<br /><br />All the carbs have been completely cleaned and rebuilt and I am 99% sure it's not a clogged carb problem. There was no change in the problem before and after the rebuilds. <br /><br />I have also talked to other suzuki owners who have had similar probelms and I'd appreicate and advice as to what may be causing this. <br /><br />Thanks,<br />Rob A.

 

[Lasse Lehtonen]

Re: 88 DT-200's have no mid range?

What happens if you try slowing speed from 3000 rpm? Do both motors rew fast down to 1800 rpm?Your problem sounds weird cause you have two engines, I have an old evinrude 60 and it did the same. I started solving the problem and the other of 2 cylinders was no spark at trolling speeds, but when I accelerated the other cylinder started to ignite again and the speed accelerated near top-end.

 

[R_Andersen]

Re: 88 DT-200's have no mid range?

Yes, if I then back off the throttles from 3000 rpm both motors slow to about 1800 rpm. <br /><br />When they jump up from 1800 to 3000 rpm is is a gradual increase even though the throttles stay in the same place. It probably takes 5 seconds to go from 1800 to 3000. I've tried everything I can think of to get themn to run at a steady speed between 1800 and 3000 and nothing works....<br /><br />My only thought could be something in the ignition causing a large timing increase past the 1800 rpm point that causes the jump in speed though I have no idea what to check.<br /><br />Thanks Again,<br />Rob

 

[Lasse Lehtonen]

Re: 88 DT-200's have no mid range?

There should be line markings in the flywheel (top of the powerhead)Have you checked them? If not check at they are all in line and if they are not, turn the outer ring to get them in to line. These lines are for the ignition timing and timing is right when the markings are in line.Have you checked the compression in cylinders? If you havent you may better run the compression test so you know where to look for the problem.If the compression seems to be good (nearly the same reading in all cylinders +- 10%) the problem is propably in the ignition.

 

[jim dozier]

Re: 88 DT-200's have no mid range?

I don't have the answer to your problem and I don't know the particulars of that engine setup but maybe I can suggest a couple of things to look into.<br /><br />The fact that both engines do the same thing suggests that the same thing is wrong with both engines, so it's probably not something like an isolated piece of crud in one carb or a fouled spark plug. Dirty carbs would probably express themselves a little different in each engine. A fuel restriction in the common fuel tank would also probably have more effect at higher rpms and not just at low-mid-range. It sounds to me like this might be a quirk of the synchronization of the ignition timing with the carb throttle butterflies. Does this engine use a mechanical ignition advance or an electronic ignition advance? Does it have a throttle position sensor (TPS) on the carbs? I would suggest that you look into the synchroniztion of the linkages for the ignition and throttle. They could have been set the same way (wrong) on both engines and a minor adjustment might allow a smoother transiton in throttle-up. Most 2-stroke outboards use ignition advance for the early throttle-up and the carb butterflies don't hardy open up until well into mid-throttle. Maybe your butterflies are coming in too early or too late or maybe one of the carbs is out of step with the others. Keep us posted on the results. I can't believe your situation is correct for those engines.

 

[mrdelgado]

Re: 88 DT-200's have no mid range?

I have an 87 DT200 on my Mako and I have the same issue. I don't think it's the engines fault. It's more of your hull design that is at fault. Your hull is designed to get on plane quick, so the faster you go, the more boat that comes out of the water, less boat in water = less resistance and the engine doesn't know that, it's working just as hard. So to fix it, get fatter fishing buddies or if not already, trim your engines all the way down

 

[Lasse Lehtonen]

Re: 88 DT-200's have no mid range?

The problem mrdelgado described is easy to test with using only other of those two engines, one engine cannot get the boat plane at 1800 rew speeds.Try to use only the other engine and look what happends when you reach the 1800 rew limit and put slightly more throttle. If the boats shape is the problem the motor will run rew:s between 1800 and 3000, but if the problem is in the engine it will try to reach that 3000 rew depending on your props it will or not reach the reading 3000 alone without other motor helping.

 

[R_Andersen]

Re: 88 DT-200's have no mid range?

It's definately the motors, since the they act the same way if I only run on 1 motor. I will have to try syncronizing the carbs.<br /><br />The boat also has electronic timing advance with a throttle position sensor so I will check the settings on them also.<br /><br />Thanks for the advice,<br />Rob

 

[Lasse Lehtonen]

Re: 88 DT-200's have no mid range?

Im now thinking that there is no problem with engines but with their electronic control because the same problem with both engines would be so special.All electronics wich are for both of those engines may cause this problem.Is there a synchronizing for motors at they are running just at the same rpm both when cruising? I have seen same kinds of problems with much bigger Mtu diesel boat engines with synchronizion.If the problem is only with one engine, the synchronizing system wants to run them at the same rpm and then you might taught there is a problem with both engines. If you cant solve the problem in other way try disconnecting both engines from electronics controlling both motors and then try to run them alone.

 

[R_Andersen]

Re: 88 DT-200's have no mid range?

Thanks again for the advice. There is no syncronizer or anything else that could control the motors. Hopefully I get some free time next weekend to re-sync the carbs and set the TPS sensor.<br /><br />-Rob

 

[Lasse Lehtonen]

Re: 88 DT-200's have no mid range?

Be careful when adjusting your carbs.If one cylinder is running lean it may burn a hole in your piston.It may also be the fuel pumps causing this problem when they were last changed? I still believe there is something, maybe that electric timing causing both motors to act like this.

 

[jay dezman]

Re: 88 DT-200's have no mid range?

double check the idle screw settings. the factory manual gives about a 1/2 turn range if i recall, check where they are set now by slowly turning them in until there is the resistance of bottoming out counting the turns as you go. do not force them at this point. <br /><br />reset them toward the minimum, making sure you don't have a lean miss at idle. retest.<br /><br />my guess is that they (idle screws) may be on the rich side.

 

[jafa]

Re: 88 DT-200's have no mid range?

FWIW , my suzuki(dt40) allows about the first 1/3 of the throttle movement to act purely on the timing, moving it by 7 degs before the butterflies even move (stator base moves). As the engine hits 1000 rpm them the electronic ignition starts to add in timing change upto 18 degs. Giving 25 degs total at WOT.

 

[R_Andersen]

Re: 88 DT-200's have no mid range?

Originally posted by jay dezman:<br /> double check the idle screw settings. the factory manual gives about a 1/2 turn range if i recall, check where they are set now by slowly turning them in until there is the resistance of bottoming out counting the turns as you go. do not force them at this point. <br /><br />reset them toward the minimum, making sure you don't have a lean miss at idle. retest.<br /><br />my guess is that they (idle screws) may be on the rich side.

Jay, you may be on to something here. I believe the factory setting for the idle screws is 1-1/4 to 1 1/2 turns or something close to that. I know that I'm running closer to 2 or 2 1/4 turns on them. I forget exactly why I have it set that way but I remember opening them up a little for a reason. I think it helped smooth out the idle but I forget exactly.<br /><br />I'm just curious why the idle mixture screws would have an effect on the lower midrange operation where i'm having the problems? <br /><br />Thanks again for all the advice,<br />Rob

 

[jay dezman]

Re: 88 DT-200's have no mid range?

while there are differences in carb designs, they all have "crossover points" where they transition from one "system" to the next...ie from the low or idle system to part throttle and finally full throttle. the screws adjust only the idle system (i believe) but if they are too rich it will "carry over" somewhat.