DT75 Issues

let0927

Seaman Apprentice
Joined
Feb 22, 2009
Messages
31
Hey all,

So far, I and a friend have been working on my outboard that I bought from craigslist for 2 months now. The old powerhead had bad compression so we replaced the powerhead and transferred all the old electrical over (including flywheel). We took her out today and she worked way better except for she won't get on and go. She maxes out at about 15 mph. We have compression and fire in all the coils and cylinders. My friend thinks its an ignition or carb problem. We have rebuilt the fuel pump with the kit from Brown's Point, cleaned the fuel filter, and opened and cleaned the carbs (did not replace anything, just cleaned with carb cleaner).

Here is what happens when we put it in gear
1) Kicks in and starts to accelerate (had to let her warm up before she would stay in gear when putting in gear)
2) Push her all the way down and the bow raises only the max speed is only about 15 mph
3) Basically, we were at the lake driving in circles today trying to make adjustments.

What do you guys think?
 

stylesabu

Master Chief Petty Officer
Joined
Aug 2, 2009
Messages
849
Re: DT75 Issues

need more info. But I own this motor so i will try to help. is boat less than 18ft? from what you state, you have no history on this motor other than what you ghave done. 1st thing is lets try enriching fuel mixture. easist way mix gas and 2 stroke oil in spray bottle.spray air intake area with engine running, if this bring up power and rpm its a fuel problem. if carbs sat a while, they need to be rebuilt/cleaned and not just with carb clean. you may need to send thin wire thriough jets, old dried gas is hard to disolve with just carb cleaner in a can,it needs the help of the wire. weak spark can cause this but fuel is much more likely. try enriching, and let me know
 

99yam40

Fleet Admiral
Joined
Sep 7, 2008
Messages
9,116
Re: DT75 Issues

Also check to make sure timing is doing its thing(Advancing as it is suppose to)
 

let0927

Seaman Apprentice
Joined
Feb 22, 2009
Messages
31
Re: DT75 Issues

I'll try the fuel enriching when I take her back out this weekend. I just remembered that there was some gas mixture backing out of the carbs. Does that indicate anything? 99yam40, how do I check the timing? Do I need to get a timing light or something?
 

99yam40

Fleet Admiral
Joined
Sep 7, 2008
Messages
9,116
Re: DT75 Issues

Yes an inductive timing light same as the ones used for automotive, and it will show if it is loosing spark on certain cylinders if you move it to the different plug wires
What are the compression readings on all cylinders?
 

let0927

Seaman Apprentice
Joined
Feb 22, 2009
Messages
31
Re: DT75 Issues

I haven't checked compression. I just bought the powerhead from ebay advertised as less than 1% leakage. I'll check this weekend, there is a money back guarantee. How do you adjust the timing if it is the timing?
 

99yam40

Fleet Admiral
Joined
Sep 7, 2008
Messages
9,116
Re: DT75 Issues

Not sure on that motor but most are controlled electronically, A service manual should give you all the info needed
 

let0927

Seaman Apprentice
Joined
Feb 22, 2009
Messages
31
Re: DT75 Issues

I've looked at rebuild kits on here and they only come with the gaskets and a replacement needle. Shouldn't they come with the float and jets?
 

cassabby

Cadet
Joined
Mar 24, 2011
Messages
11
Re: DT75 Issues

Hello, I've got your motor on the back of my boat for the last 16 years. My first question is what prop pitch are you running...it could be far more prop than your rig calls for. I am running a Bayliner MS1500 Misqueto 14.25' boat and can only turn a 16P SS prop at 5200-5300 rpm. I have the 85 hp upgade as well. I think I may be able to help with more info. cassabby
 

mphelle8vld

Petty Officer 1st Class
Joined
Aug 17, 2005
Messages
321
Re: DT75 Issues

I've looked at rebuild kits on here and they only come with the gaskets and a replacement needle. Shouldn't they come with the float and jets?

Floats usually don't go bad, jets need only to be cleaned. Just be sure and not mix the jets between carbs while cleaning.

Nice that you were able to swap your components on to the new powerhead, but given that it's an Ebay purchase, check the compression before the guarantee expires. If you think your carbs are clean, check the timing, your manual will tell you what timing marks to look for at the appropriate rpm.

What year or model/serial number is your motor?
 

let0927

Seaman Apprentice
Joined
Feb 22, 2009
Messages
31
Re: DT75 Issues

Floats usually don't go bad, jets need only to be cleaned. Just be sure and not mix the jets between carbs while cleaning.

Nice that you were able to swap your components on to the new powerhead, but given that it's an Ebay purchase, check the compression before the guarantee expires. If you think your carbs are clean, check the timing, your manual will tell you what timing marks to look for at the appropriate rpm.

What year or model/serial number is your motor?

The powerhead is an 88, the original is an 83. The powerhead transferred nicely except I had to move the carburetor manifolds too because the oil pump valves were located in different spots.

As far as the prop, should the bow be rising up at no faster than 20 mph? I'll check the pitch this weekend when I do the other suggested things.
 

mphelle8vld

Petty Officer 1st Class
Joined
Aug 17, 2005
Messages
321
Re: DT75 Issues

I haven't checked compression. I just bought the powerhead from ebay advertised as less than 1% leakage. I'll check this weekend, there is a money back guarantee. How do you adjust the timing if it is the timing?

Timing on the 83 is adjusted with the linkage that attaches the throttle linkage to your rotating timing base thats mounted under the flywheel. You may be close when you swapped your components over but it wouldn't take much error to put a hole in a piston. If you don't have a good manual to set up the timing, buy this one:http://cgi.ebay.com/ebaymotors/Suzu...00411898267QQptZMotorsQ5fManualsQ5fLiterature

Post what you find on the timing issue, your compression results, and then we can address whether or not the motor can spin a stock prop around 5500rpm. Then on to boat setup
 

let0927

Seaman Apprentice
Joined
Feb 22, 2009
Messages
31
Re: DT75 Issues

Will do, I have exams coming up so I have been spending all free time on Law School. I'll update after exams. Thanks.
 

let0927

Seaman Apprentice
Joined
Feb 22, 2009
Messages
31
Re: DT75 Issues

So I'm just now getting back to the boat after buying a house with my wife. I'm pretty sure its the timing since we moved the timer/idle adjuster like crazy when changing over the new powerhead. Anyone have any suggestions on what procedure? My manual outlines a pretty basic procedure but I will be doing it in the backyard. Any suggestions are greatly appreciated. Thanks
 

let0927

Seaman Apprentice
Joined
Feb 22, 2009
Messages
31
Re: DT75 Issues

I'm certain its the timing and I bought a tachometer tester. My question is where do I connect the leads? I know one goes to ground but where do I connect the other one? The starter?
 

99yam40

Fleet Admiral
Joined
Sep 7, 2008
Messages
9,116
Re: DT75 Issues

the only person that has any idea of what tachometer/voltmeter tester you came up with is you
 

let0927

Seaman Apprentice
Joined
Feb 22, 2009
Messages
31
Re: DT75 Issues

I bought this off of Amazon. I'm pretty sure its a general type of tachometer. I want to know where does the actual clip hook to in order to determine the R.P.M.s of the engine.
 

99yam40

Fleet Admiral
Joined
Sep 7, 2008
Messages
9,116
Re: DT75 Issues

Read the manual that came with it.

I have never seen a tachometer/voltmeter tester so who knows what you have
 
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