Normal?

[graphicjunkie]

Ok, so took new boat out today. Amazed at how much more space we had, and couldn't be more happy. Got the kids out on the tube and went to 'crank it up'...and there just wasn't anything there. Our old boat was a 17' with 50hp force OB...and it did about 25 on the water. This boat, 19' with 125hp Force OB, we were peaking at 16mph according to the GPS!!! The RPM's never went above 3K (floored!!)
I tried trim up, down, middle...you name it.

So now that I'm done venting, my questions.

1) What RPM's should that engine be able to run at? Full throttle the tack settled in at around 25-2600 RPM. I guess I'm used to 2 stroke bike engines that rev. So I was expecting 4-5K.

2) What other issues could have been causing it? Fresh gas, 50:1 as discussed in an earlier thread.

I know this boat is 2' longer. But I have almost three times the power.... I don't expect 80mph on the water, but 35 would be nice!

 

[jerryjerry05]

Re: Normal?

Your right you should get 5500 RPM.
Basics.Compression/spark test.Fuel system.Diaphram.Plugs burning right?
Make sure the tach is working right.Do these tests and post your results.J

 

[87blf125]

Re: Normal?

you should pull between 35 and 40, what pitch prop do you have on, should be around 17 pitch or 15

 

[brianvolt7]

Re: Normal?

I have a 1990 Bayliner cuddy 20' with a 125 block, 120 housing and leg and an 85 hp lower unit- Its a long story.

I just clocked mine on plane WOT with the GPS at 32.

 

[robms6]

Re: Normal?

I would do a compression test to see if that is your problem. Look at your plugs while they are out and even hit them with a little carb cleaner to take off some glaze. HOPEFULLY your compression is fine. Then its time to start looking at your carbs / timing. If your compression is below 115 I would pull off the head. Hopefully its just a blown gasket. Its only 18 bolts

GL buddy

 

[jason32038]

Re: Normal?

First check compression and if that's good look for loose or broken wires at the cd modules. Sounds like you're running on 3 cyls.

 

[pelletman]

Re: Normal?

I'm getting exactly the same numbers out of my unit. A 1989 125hp that I
have very little experience with. It starts up beautifully, runs well and
sounds well. But on my 20' Maxum I can only pick up 3000 rpm. I was wondering the same thing. In my case I believe the loading has a lot to do with it. We had 5 teens on the boat plus one on the tube. With three
total on the boat the week before it was MUCH faster.

 

[87blf125]

Re: Normal?

ok, i have an 88 18 ft bayliner with a 125 and a 17 pitch ss prop, it pulls 35 -40 depending on the load at around 4000 rpm. my buddy just bought an 88 19 ft bayliner capri with a 125, he pulls between 37 -40 with a ss 17 pitch prop, not sure his rpm. i just again am wondering what pitch you are running, too big could be causing all the problems and it may not be mechanical???

 

[Swe-Bayliner-89]

Re: Normal?

I'm thinking like Jason - it might be missing one or more cylinders.
It's pretty hard to hear if you're not used to it.

You could either try running the engine with only one spark plug connected at a time - or buy an ignition tester - very cheap.
Get a compression tester too while you're at it.

 

[graphicjunkie]

Re: Normal?

so the weather isn't cooperating for me. Each time I try to get to it, it starts to rain on me.

My prop is a 523-17, so it's a 17 pitch. I do have an extra 519-15 though. But I won't start playing with pitches and rpm's until I believe the boat is operational.
Both of my ignition modules look brand new.
I took out all the spark plugs (all were filthy) and cleaned them off. Will try the one at a time test hopefully tomorrow. Plan on just replacing all of them.
Will also run a compression test.

I did install a sting ray XPii today, those are supposed to really do wonders.
I tried to also install a transom saver, but my trailer doesn't have a beam that crosses right at the back...so that will have to go back to the store...grr....

But it's hard to do these tests also by yourself.
I DID find a TON of fishing line behind the prop all wrapped around the shaft. Took me a while to clean all that off!

 

[jerryjerry05]

Re: Normal?

Compression test then spark test.With a 125/120 head and an 85 lower your performabce won't be as great but should do way better than that.
Then check the fuel pump diaphram.Then get a second tank and try running it on that.J

 

[87blf125]

Re: Normal?

i had a stingay hydrofoil on my boat and actually lost speed and ran into more problems with it being, on like when i was on plane it would raise the back of my boat too much

 

[graphicjunkie]

Re: Normal?

So today I tore it all down and checked for spark, and compression, and so on.

I don't know the firing order, so I'll just reference 1-4 from top to bottom.

I don't know how much compression they SHOULD have, but all cylinders were right on the money at about 127 psi. That made me REAL happy that they are at least consistant. I believe I heard somewhere 130 is optimal?

Anyway, cylinder #2 had no spark. Had an extra coil, so I swapped that out.
Now #2 has spark, and I'm firing on all four cylinders. (Now THAT's QUESTIONABLE!! )

So with having cleaned all the fishing line off the prop, getting spark, having cleaned and de-carboned each plug...we decided to take the boat out today for a test spin.

WOW!!!! RPM's hit 4600, and now the boat hauls @$$! TOTALLY different boat now! AND I wouldn't doubt that the carbs could still use a bit of a tune up. That's my next project. Also, my prop is beat up bad. I'm sure a new prop would also increase performance.

Thanks for all the help!

Some pics for fun, hope no one minds.

For the same price of this...
17' bare bones, stereo, manual trim, 50hp engine.

Now we have this...model is six years older, but in better shape!
19', electric trim, stereo, fish/depth finder, etc...etc...

 

[jerryjerry05]

Re: Normal?

You should still be able to hit 5500rpm.Make sure the prop is good.The boat with too many people will affect rpm.
What prop is on there? J

 

[Swe-Bayliner-89]

Re: Normal?

Wow - she is beautiful!
Glad to see you found the problem and could fix it.

127psi is great - doesn't have to be 130.
Above all it's really good that they're all the same compression.

 

[graphicjunkie]

Re: Normal?

Thanks for the comps.


Prop is 523-17, but it is really in bad shape. I plan on replacing for sure.
Yesterday we had only my wife, my kids (7&5), and myself. So MAYBE 400lbs?