Questions about a DF60.

[emilime75]

I have a friend with a 2002 Crest 22' pontoon boat and a Suzuki DF60 4 stroke motor. The motor should also be around the 2002 model year, they were bought new at the same time as a package.
Yesterday, we took it out for the first time this year, and everything was fine until we hit full throttle. Usually full throttle was between 4200 and 4400 rpm. This time if we tried going above 3900/4000 rpm it seemed as the prop was momentarily slipping. The engine sound changed and the tach jumped up for a brief moment and then back down. At first I thought it was missing as the boat lightly jerked everytime it happened but then as I watched the tach I noticed it jumping up everytime it occurred. Below 3900 rpm we didn't have any problems.

Does the above sound like a slipping prop or some other problem? I am trying to help him out as much as I can as he's older and has had major back surgery and is still recovering.

Aside from that, I would like to do some maintenance on the motor for him, like change the oil, replace the water pump/impeller, fuel filter... can these things be done with the boat in the water? We have no trailor for it and it is docked in about 2-3 feet of water.

We'd appreciate any ideas/thoughts regarding these questions. Thanks.

 

[JB]

Re: Questions about a DF60.

First of all, I suspect that you have the wrong prop. WOT should be a lot higher. My DF70 was WOT at 5800. The DF60 is essentially a detuned DF70.

That could cause cavitation, which may be his problem, though it sounds more like a failing hub.

 

[emilime75]

Re: Questions about a DF60.

Well, that's very interesting. A quick search after reading your comment reveals max output for that motor to be in the 4700 to 5300 range, so appearently it is propped incorrectly.

This boat got a lot of use last summer and the problem was never noticed until now. I don't think it's cavitatioon issue.

How would one go about choosing the correct prop for this motor/boat combo?

If our problem is prop slip, would a new prop fix this or are other parts necessary?

 

[JB]

Re: Questions about a DF60.

Post in the Prop Forum to get help with prop selection. If you have a slipping hub a new prop will solve it.

Good luck.

 

[Silvertip]

Re: Questions about a DF60.

I don't think this is a prop issue. I think the engine is actually suffering a misfire and when you see the tach jump the bad cylinder is coming back to life momentarily. This would be confirmed by the jerk you feel when that cylinder begins firing. A bad prop may slip but you don't feel a jerk. It may appear to be running smooth below 3900 rpm but the cylinder is not firing at all at that rpm so you don't feel the jerk which makes you feel things are normal. Don't spend money on a prop until you know for sure which end of this engine is causing the problem. With the engine running properly the prop you have may indeed be correct. That engine should idle so smooth you could set a wine glass on the cover and it wouldn't fall off (almost anyway). If the engine is jiggling excessively, then it has a problem. A spark plug check can tell you alot about the fuel and ignition system performance.

 

[emilime75]

Re: Questions about a DF60.

Thanks Silvertip, but it's not a misfire. The engine runs and idles very well. Maybe my choice of words is misleading, when I said "jerk" I should have said the boat actually lost speed for a brief moment. Like I said, at first it did seem like a misfire but with the tach jumping up and the boat loosing speed I figured it was probably prop slip. Sorry for the confusion.

JB, thanks for the replies, I will ask my prop questions in the prop section.

 

[DaveG]

Re: Questions about a DF60.

I have a DF70 and the motor acted just like your problem. I changed spark plugs and the problem was fixed. At only $2/plug it is worth a try.

 

[Silvertip]

Re: Questions about a DF60.

You have not checked the plugs and read them? Until you do that all the disagreement will not solve the issue. Besides, that engine should rev much higher than it is so if the prop was the issue (slipping) the tach would rev off the scale. Do some checks -- don't just say "it can't be a misfire". And whether you think the engine is running smoothly or not, many folks don't know what an engine feels like when one cylinder is misfiring. Smooth to one person is rough as a cob to another. Do a spark check and plug reading immediately after a wide open throttle run. DON'T idle the engine after the run. WOT for 1/2 mile or so then kill the engine and check the plugs. Tan = fine. White = misfiring due to lack of fuel or no fire Black, oily, fuel soaked = rich and or possibly not firing. How much old fuel is in the tank and if the boat just came out of long term storage, was the fuel treated with Stabil or SeaFoam (or any other fuel treatment) before storage? If not it should be used all the time.