My wife bought me a boat with a 1995 Suzuki DT85 for B-day - Sweet!
Repair Manual ordered but not here yet.
Motor starts fine, idles fine and when motor is cold I can get full speed.
When motor warms the most speed I can get is about 5.5 mph (land.)
I moved fuel tank from stern to bow (17 feet) with one (1) new fuel line.
I have fuel filters on both the fuel line and inside the motor and replaced both.
Put in new spark plugs.
Same result - when motor is warm I get about 5.5 mph, more than that result in motor shutting down.
"Idiot lights" show all is well.
No idea when previous owner had the motor last serviced, inside the skin looks clean, very little salt water residue but the old plugs may have been the originals, they looked oily rather than burned.
Is there a place on a Suzuki motor showing number of hours since last service? Can the number of hours be reset?
My hope is to be able to use the boat until the end of the season and then take her in for a fully physical so if someone could give me some ideas what may be need to be replaced to get me by until then it would be very much appreciated.
Anyone who tries to run a motor without a clear service history is asking for a blown motor. At the very least the carbs need cleaning, that means disassembly, the oiling system needs to be tested to specs and the lower unit needs to be pulled and the pump impeller and oil needs changing. A compression check would not be a bad idea along with a new set of plugs. That will give you some idea as to the condition of the motor and forwarning of possible failure.
Dont take a probable good motor and destroy it.
I have the exact same engine with the exact same or similar problem.
I had my mechanic look at this. He is not able to recreate the problem (because it only happens when the engine is warm).
The mechanic has already done the following...
-changed my plugs
-changed the fuel filter
-done a service
-cleaned the carbs (only by flushing engine cleaner through it, but not taking them apart)
-he has checked the fuel pump
-he has checked my fuel for air water in the fuel
symptoms of the boat...
-runs forever if you don't touch the throttle
-throttle fine when engine cold
-when enging running hot, only runs when you hammer the throttle
-if you run at low rpms it cuts out (when warm)
my mechanic says a carb rebuid may fix it but he is not 100% sure. from what he can see (without taking them apart), the carbs are fine.
one suggestion i was told is that the choke could be sticking. i have to check this.
choke should open with full throttle, check linkage. its called a choke unloader. make sure its working. choke should be fully open when throttle is all the way open. Also enrich full mixture to determine if its a fuel problem easiest way is a hose attached to porpane cylinder. put end of hose in front of carb intake and open valve on propane when engine starts to stumble.if it doesn't change. then problem is elsewhere.i have seen coils fail when they get hot, i would then look into secondary ignition. module , coil, trigger. A wek spark can cause you condition. it either spark or fuel. a warm engine shouldn't change internally from when it was cold. meaning an engine is going to loose compression just cause it warms