suzuki dt65, runs great but........

Hi,
I recently bought my first fishing boat, its a Wilson Flyer 17ft (planing hull). The boat is powered by a 1991 Suzuki dt65.
After purchasing the boat, I took it to my local boat yard for one or two jobs, rewiring the cabin, a few electrical jobs.
I decided to have the engine serviced at the same time. Ive since got the boat back, serviced. The mechanic told me he had tuned the carbs also, and checked the engine over, he also commented it had been looked after and was in good order.
The boat starts fine, even after its been stood a while, revs up fine and generally sounds great.
I was however on first run out surprised that it didnt seem as quick at top end as I imagined.

I initially thought the engine was over propped, and also had a tach fitted.

First run out after this the boat was pulling 18 knots @4000 rpm.

Changed down 4 sizes in pitch boat is now pulling 20 knots @4200rpm
It also now sounds like its on the/a limiter??.

From a start up to 4000 rpm, its fine then just seems to run out of steam.

could it be fuel starvation? or something more sinister.

I have a general understanding of engines, but anyone who has knowledge of this engine who is willing to give me a few pointers then Id be most grateful.


Joel

Re: suzuki dt65, runs great but........

check compression and spark on all cylinders, and see if timing is advancing properly.
check timing and spark at problem RPM also, if all is good then you are left with fuel problem.
http://forums.iboats.com/showthread.php?t=283363

Re: suzuki dt65, runs great but........

As above, If you didn't check the compression before buying, post what the numbers are now. When the mechanic "tuned" the carbs, does that mean he took them apart and cleaned them? If the motor had been stored for awhile, he should have told you to run pre-mix for awhile until you verify the oil injection is functioning properly. What size prop are you running?

Re: suzuki dt65, runs great but........

Thanks for the replies guys,
I was running a standard 11.5x16 prop, and have since dropped to a 11.5 x 12 prop both props are genuine suzuki, same model props.

I have noticed however that since moving to the smaller pitch prop I have gained a little bit of speed, fuel consumption seems slightly better, tho according to the tach I have only gained around 200 rpm's.

Would it be possible that this engine is running fine? and I am actually flat out as it were? and the tach has been wired up incorrectly??

The limiter noise/ slight missing is just that, I am actually on the limiter? but I am getting an incorrect tach reading?

Regards
Joel

Re: suzuki dt65, runs great but........

Wasn't familiar with the Wilson so I found this, http://www.fishing-boats.info/wilson17.htm The limiter is set at 5900, you need to verify your tach is accurate and then prop it for around 5500. If your tach is correct, you have a sick motor.

Re: suzuki dt65, runs great but........

Thanks for the replies guys, before I start, would anyone be able to identify which setting I need my tach on?/ how many poles?
I'm not convinced rpm reading is correct, engine is a 91 dt65.
Thanks for all your time.
Regards
Joel

Re: suzuki dt65, runs great but........

6 pole according to http://faria-instruments.com/site_manuals/IS0012u.pdf