Bad valves new engine??

ERICAR · Oct 5, 2008

I have a 2007 Bayliner Discovery 246 with a 5.7 250 hp with 48 hours on it. She started to lose power, ping, rpm's keep decreasing. Had the mechanic look at it, long story short, the intake valves tuliped. They replaced the valves with stainless steel valves and now he wants to change the gear drive from a 2.20:1 to a 2.43:1. Has anyone else heard of such a thing on a new boat??

achris · Oct 5, 2008

Re: Bad valves new engine??

If he's trying to get the revs up, then it's a whole lot cheaper to change the prop for the next size down. Unless you're operating the boat above 5,000 feet, leave the gear ratio alone.

Chris.......

ERICAR · Oct 5, 2008

Re: Bad valves new engine??

Yes, he is trying to increase the WOT rpm to 5000. How does a differant prop or gears efect performance?? She has a Bravo 3 with a 22 in. pitch.

krisnowicki · Oct 5, 2008

Re: Bad valves new engine??

is bayliner doing this or are you paying for it?

ERICAR · Oct 5, 2008

Re: Bad valves new engine??

It's still under warrenty

achris · Oct 5, 2008

Re: Bad valves new engine??

Just like the gears in your car... If you try being in a gear higher than you should be for a given speed/road gradient, then you have an idea of what's happening with your boat. What are the max revs now? Each 1" decrease of pitch change will increase the revs by about 200.

Chris..........

ERICAR · Oct 5, 2008

Re: Bad valves new engine??

It's getting 4350 right now.

achris · Oct 5, 2008

Re: Bad valves new engine??

I'd be putting 20" props on and leaving the gear ratio alone... That should get you up to 4800ish, which is right in the middle of your recommended range (4600-5000).

Chris.........

P.S. The propping should have been done before you took delivery of the boat... That is just poor set-up and commissioning by the dealer.

TilliamWe · Oct 5, 2008

Re: Bad valves new engine??

Eric, I know exactly why the engine did this, and why they want to change the gears. The boat's bottom was fouled (dirty) for a portion of those 48 engine hours. That caused the engine to not be able to hit the recommended WOT RPM range. That caused excessive heat in the combustion chamber, which deformed (tulipped) your valves. Don't ask me how I know this, but you can guess.

The reason he wants to regear is that a switch to 20" props won't raise the revs to the 5200 mark he wants. But be advised, he's wrong if he wants it to turn that high of RPMs. You 5.7 is a carbureted engine and the Mercruiser WOT range is 4400-4800. If it was fuel injected it would be 4600-5000. But not 5200. So, you need to try the 20" propset (which is the lowest you can get in a Bravo 3) and see if it raises the WOT RPMS to the upper end of that 44-4800 range. If it does, you are done. And keep the bottom of the boat and the outdrive clean and free of marine growth. You'll be fine.

BaileysBoat · Oct 5, 2008

Re: Bad valves new engine??

Like Achris said, too bad the dealer didn't prop the boat before delivery. I'd be inclined to do as TillamWe said and try a 20p before changing gears. Was that 4350 with a heavy load?

Don S · Oct 5, 2008

Re: Bad valves new engine??

Are you using the trim properly? Is there too much weight forward or aft to get the boat to plane properly?

JustJason · Oct 5, 2008

Re: Bad valves new engine??

the 64,000 question is, has the boat had a 4350rpm WOT since new? or was it higher when it was new, and now has become lower? Also.... and only you will know this, but are you overloading the boat with weight?
And lastly.... is this 4350 with the boat tach or a known good shop tach?
an 07 boat tach is probably OK... but stranger things have happened.

ERICAR · Oct 5, 2008

Re: Bad valves new engine??

You guys are good. The so clled PDI was never done, I have a blank form in my doc package. Mercury also thought the bottom was fouled but this is a rack boat and the bottom looks like the day I looked at her in the show room. The 4350 was with a minimal load, the mechanic, 20 gallons of fuel and 20 gallons of water, 150 lbs. of gear. The boat always planned quickly, that never seemed to be a problem. As far as did I get 4350 after delivery? honestly I was looking more at the speedometer, and that was hitting 45 mph with 5 adults full gas (80 gal.) 20 gal. of water WOT.

Don S · Oct 5, 2008

Re: Bad valves new engine??

That's the problem with a lot of the smaller boat dealers any more.
They don't do any of the requiered PDI's for either the boat or the engine.
Just get the boat in and sell it for the most amount of profit.
When we sold a new boat, all the PDI's and other paper work was done, sent to the boat dealers and engine mfg. The new owners were also taken out for a shake down run for an hour or two to show them how to use the boat and every system on the boat.

ERICAR · Oct 5, 2008

Re: Bad valves new engine??

Yup, your right, the dealer was terrible. The PDI was just the beginning, good thing the marina where I keep her has a Mercury approved mechanic.

TilliamWe · Oct 6, 2008

Re: Bad valves new engine??

ERICAR said:
You guys are good. The so clled PDI was never done, I have a blank form in my doc package. Mercury also thought the bottom was fouled but this is a rack boat and the bottom looks like the day I looked at her in the show room. The 4350 was with a minimal load, the mechanic, 20 gallons of fuel and 20 gallons of water, 150 lbs. of gear. The boat always planned quickly, that never seemed to be a problem. As far as did I get 4350 after delivery? honestly I was looking more at the speedometer, and that was hitting 45 mph with 5 adults full gas (80 gal.) 20 gal. of water WOT.

Okay, the boat planed quickly and would run good with 5 adults on board, full of gas and water? I think the motor is sick. And not just the valves. Mercruiser did put in the 2.20 ratio drive which is the lowest gear ratio they are supposed to offer on a boat that isn't at high elevations. And then a 22 pitch propset is the second lowest you can get. That is unusual for a Mercruiser powered boat to need that much help. I don't think the carbed 250hp 5.7 is quite enough motor for that boat, and it may have been the base engine, but it should still do better than what you are getting, with a 2.20 ratio and 22p props. Is the engine getting full throttle opening after the valve job?

ERICAR · Oct 6, 2008

Re: Bad valves new engine??

Yes, I had her out Sat. and she got 4400 easily and felt like she still wanted to climb. I couldn't keep her there long, seas were choppy, engine temp. 175, oil pressure 46 ish. Two adults, 60 gallons of fuel, 20 of water. When you say you think the motor is sick, what are you referring to?

Bondo · Oct 6, 2008

Re: Bad valves new engine??

Yes, I had her out Sat. and she got 4400 easily and felt like she still wanted to climb.

Ayuh,....

Unfortunately,.... We can't diagnose using speculative specifications.....

I wouldn't, couldn't, state a reliable rpm at WOT without a minute at Speed...
I don't like twisting'em that tight for a Long time, but a minute is an Honest result....
Clean water,+ Trimmed properly....

It's not about how much throttle is left, or whether she feels like it mght go still faster....

That said,.....
I agree with Everyone that your motor is Over-Laboring,.. Detonating,..
For some reason....

ERICAR · Oct 6, 2008

Re: Bad valves new engine??

I agree, that's why I said I couldn't keep her there long due to weather, although I did have her at WOT for over 3 minutes. She was evenly trimmed as well.

Bad valves new engine??

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