Over revving or F-ed up tach?

[oktain]

Here's my issue, my boat seems (looking at the tach) like it's over revving. Owners manual says peak HP RPM is ~7300, tach at WOT is showing it revving right to the "A" in the Sea Doo logo.

Issue here is I was sure I read there was a rev limiter at 8000? I'm wondering if my tach is wrong.

What are you guys revving at while cruising around 25-30mph? Last time I was out I couldn't get my boat under 6500 RPM, which struck me as weird because when I had it out the day before I was cruising around 4000-5500 RPM. Idle seems pretty fast too at ~2200 RPM

What are the things I should be checking? Wear Ring, obstructions in the pump?

Any help is appreciated.

 

[oktain]

Bump.

Lots of views but no input...

 

[crookieda]

Check your rpm vs speed on a gps. Compare to how it has performed historically.
That and use your ear to compare to the speed now vs what you remember. That will tell you if you have a tach or an drivetrain problem.

 

[oktain]

I'll give it a try, what's not helping my case is I've only owned the boat for a week.

Thanks.

 

[TimIHB]

I am not one of the resident experts but if the engine is reving higher and producing less speed then it is probably lost pressure somewhere. Maybe the wear ring. Take it to the dealer! Expensive but factory trained. Mine has been reasonable. I established a relationship with a mechanic there and he has been able to help me avoid several problems with good advice. I am going today because i (somone) broke the reverse gate on my boat. 200.00 plus half hour labor. it's part of owning a boat i guess. I fix all the minor things myself but somethings need to be handled by an expert. There are only so many weeks of summer, right.

 

[crookieda]

Well since you don't have alot of reference to what your boat should perform at. Hopefully someone with the same model and year boat will chime in with what you should be expecting for performance. With mine I have twin 155's and if the wear rings start going bad there will be cavatation along with that enging bouncing off the rev limiter until it gets up on plane. Then only give me about 45 mph indicated. When all is good it goes like stink up to 55 mph.

 

[oktain]

With me alone it's pretty fast up to 50 mph, it'll bounce off the limiter once for a split second when I open it up from a stop but hooks pretty good. Not the typical cavitation I've been reading about. What was weird was I was cruising at an indicated 30 mph at ~7500 rpm which seemed way too high. When I came off plane for a 5mph channel near my camp it read my normal rpms when I came back up on plane to cruise home.

Where are the tach hookups on this thing? Is the tach electronic or a cable? I've had interference from an ignition coil play games with a tach before (snowmobile).

 

[crookieda]

Tach sensor is on the top of the engine on the 4-tec n/a. From what I've read here others have had some issues with them failing. None personally knock on wood. Did you hear a difference in engine rpm when tach was different?

 

[oktain]

Now that you mention it... no, My buddy mentioned the high reading and I said it was weird because it didn't sound any higher than the day before...

I'm starting to wonder if there isn't something fishy with my tach pickup. I'll probably have to remove that plastic shroud with the 4-tec logo eh? Hopefully it's something simple causing this issue, I'll be back in the boat this weekend so I'll see if it does the same thing, if not I'll be fiddling with the tach pickup. Where exactly is it?

Thanks for the help guys.

 

[devonte007]

I have a 2004 4-tec n/a, which is virtually the same boat as yours, and I got it used as well. First thing I had to do was a new carbon seal and whole new pump and impeller. Before the propulsion system rebuild, I had a similar experience as you. When I was alone in the boat it would get up and go fairly normal with a bit of cavitation right off the bat if I floored it. Then I got a couple big dudes in the boat and it would be difficult to plane out.

Long story short, now it hooks up great and I can hammer the throttle from a standstill and no cavitation whatsoever, it never bounces off the rev limiter like it used to. I am thinking that you may need some maintenance on your propulsion system since it sounds like you experience cavitation momentarily from a hard start.

I also installed a new battery at the beginning of this year and noticed that the tach seemed to act a bit more normal from what I remember last year. I have heard that these boats can act weird sometimes if the battery (or voltage) is not very good. Anyway, I won't be back on the boat for about another week or so, but when I do get back to the lake I'll test it out and let you know what kind of readings I'm getting from my tach at certain speeds. If you can wait that long, I'll be happy to send you some more info soon.

 

[oktain]

I'd be happy to wait lol. I'll be back in the boat this weekend but I'll be pulling it out of the water. Would pump maintenance be needed at 76 hours?

As far as working on the pump, what special tools will I need? What did you replace? Carbon seal and wear ring? Anything else? Just want to know so I can order some parts.

And looks like I'll be measuring my battery's voltage after putting my new speakers in. (Just replacing the old destroyed Clarions)

 

[oktain]

Just updating.

I've run about 2 tanks of fresh fuel through the boat now and I'm very pleased. Performance has improved, tach is indicating ~7,300-7,500 RPM at WOT, according to my owner's manual that's right around the peak HP RPM. Perfect.

My "slight" cavitation is gone, the boat hooks and takes off like a scolded cat now and I couldn't be happier.

My fuel mileage has also doubled. Amazing what old fuel can do.

Just wanted to thank everyone for their input.

 

[devonte007]

I'm glad to hear that everything is back to normal. Amazing how simple things like fresh gas or new spark plugs can really change how the engines run. Now you can enjoy the rest of summer!

 

[oktain]

Yessir, my next step I think is to replace the plugs and see what happens. They may be in rough shape like the fuel was lol.