Suzuki dt75hp loss of power

[michael1923]

Hi i'm new here and your my last hope, i know its been covered before but i can't find a conclusive answer that i haven't checked, apologies for the long note but wanted to add all the info.

A few months back i bought a suzuki DT75 hp, when i purchased it, it had been sat around for about 18 months.
When i first started it, it started first time but ran really bad, very knocky at low revs, and would not rev up at all, it ran on when turned off and would not idle without some quick starting and then trying to keep it running using the throttle on the engine..

At first i put it down to needing a general service.

I have done the following

2 new sets of spark plugs as per manual (dealer spec )
New spark plugs caps
New gearbox oil
Timing checked and adjusted
Carbs taken off and cleaned
Idle screw set 1 1/2 turns out as per manual

Now in neural starts and stops great, revs up great, abit knocky at low revs but this goes when reved up.

However put it in gear at take the boat out for a run, it lacks all power (because of the revs) it just will not rev up above probably 2000- 2500rpm. And prob does an estimated 7 knots, I am now not sure where to turn. I do not have a large budget but do have the time on my hands to slowly put things right.

I am about to check fuel pump diaphram and filter as this is mentioned in the manual, and will also add some jubilee clips as some of the fuel lines are missing them, but they seem to be really tight and i dont think its that but will add the clips just to make sure i can rule this out. Also worth noting is it is missing the air filter.

Any advice would be greatly appreciated
Mike

 

[deejaycee_2000]

Re: Suzuki dt75hp loss of power

Welcome to iboats ... .... First replace the fuel pump diaprham, then check all fuel lines for leaks and make sure they get proper clamps so there is no leaks, then make sure you have enough ventilation at the tank ..... the air filter is not a big deal but worth having ....

 

[hopalong]

Re: Suzuki dt75hp loss of power

To add, check the fuel primer bulb...make sure it pumps up and stays hard. And check the quick connect fuel fitting at the cowlin entry. There are "O" rings inside of the fitting and overtime they will become hard or bad. If this happens the fuel line at the fittings will suck air and cause the engine not rev and miss etc. You may not see any fuel leaking at the fitting but if O rings are bad it will suck air and not leak fuel outside of fitting. By temporarily removing the fitting from the bulb side of the hose and attaching the hose directly to the male end from the fitting to the motor or to the fuel filter will bypasout the quick connect to see if it is sucking air. Replace the entire ftting male and female if it is bad or use a barb/barb fitting in lieu of the quick connect.
BTW needle at the carb/float could be sticking and would restrict full fuel supply to the engine. Are ALL of the plugs getting gas...do the condition of the plus appear to be firing?
Also if all else does not remedy problem try partially choking engine and see if it revs up, if it does fuel is being restricted somewhere,

 

[michael1923]

Re: Suzuki dt75hp loss of power

Thanks for the replies

Good points, the bulb is priming fine and staying hard, i've cleaned the carbs so i know, its not the float needle.

I will bypass the fuel connecter,that sounds like a possibility.

i have checked the spark plugs twice since fitting the second set and both times nothing apparent there, all 3 a nice tan colour.
I'm just about to check all fuel lines and possibly change them, would a tiny air leak cause this much trouble.

Mike

 

[hopalong]

Re: Suzuki dt75hp loss of power

very possible IMO

 

[deejaycee_2000]

Re: Suzuki dt75hp loss of power

very possible indeed, if all else fails ... check the reed valves

 

[michael1923]

Re: Suzuki dt75hp loss of power

Sorry what does IMO stand for

Mike

 

[hopalong]

Re: Suzuki dt75hp loss of power

In most internet forums and other cyber world areas it is slang for In My Opinion

 

[michael1923]

Re: Suzuki dt75hp loss of power

Thanks for the help

Mike

 

[grid]

Re: Suzuki dt75hp loss of power

If you suspect fuel as a problem, push in on the ignition key when you've achieved maximum RPM under load. If the engine picks up RPM momentarily, you have a blocked main jet in one of the carbs. If the engine dies, fuel delivery--at least to the operating cylinders--is okay. Try using plug cap removal pliers to remove plug caps under load to see what's firing. Have somebody else at the helm when you do that!

 

[michael1923]

Re: Suzuki dt75hp loss of power

Thanks everyone for your help, but i've finally given up.

Theres water being squirted out of the exhaust hole, so looks to big a job for me, i'll wait till january time and try and get another cheap engine.

I dont have the funds or the will anymore to sort this. Seems as though it was something else all the time.

Once again thanks for the advice.

Mike

 

[hopalong]

Re: Suzuki dt75hp loss of power

What do you mean by "exhaust hole". Note,the retangular opening on the back of the motor just below the cowl,,,water is supposed to come out of that.Is this the xhaust hole you are speaking of?

 

[michael1923]

Re: Suzuki dt75hp loss of power

Yes thats the hole, its a water spray thats a milky colour.

It comes out of there and the tell tale, I do need to give up though, i haven't got a clue where to turn. I tried to get a plate in the side of the block off to see what went on inside, and guess what snapped a load of bolts.
It's a shame really but not the end of the world. I've decided to save up some money and try to get a cheap one to get me out and about next spring.

 

[michael1923]

Re: Suzuki dt75hp loss of power

Oh forgot to say hopalong
the primer bulb stayed hard when pumped and when i connected the end directly to the fuel filter i.e. missing out the fuel pipe connector no difference.

Mike