Excalibur502mag

I actually posted this last week, but it was in the wrong forum. New member error!
I did get one response and appreciate it.

After a profitable last year, I decided to go out and find a good boat for speed and power. Living on a 300 acre lake with a 23' restriction on length, my options were slim. I would love to get a second mortgage and a 38' boat with multiple engines, but I would not be able to use it on the lake I live on.

After shopping for a while, I found what I thought was the perfect boat.
I found a 1999 23' Wellcraft Excalibur with a 502 Mag (Bravo 1 1:50).
With straight pipe 4” exhaust straight out the back, I could hardly wait to get this boat out and see what it would do.

To make this long story short, I have been very unimpressed with the performance.
The first time I took it out I had the stock 23 pitch mirage on and ran 61 mph at 4900 rpm. I was not satisfied.
I then borrowed a friends 25 pitch 3 blade prop (14 ¾”). I later realized that it was a Yamaha outboard prop, which some people said I could use, but should be careful. I was by myself, still had a good whole shot and quickly reached 69 mph. I was excited and already thinking about another prop, when the overheating alarm started to go off. After some trial and error I figured out that the impellor in the water pump was shot. I replaced this with a knowledgeable friend.
Again excited about the top speed, went out and could not get the boat over 58 mph. It is only running 4100 rpms, and I can not figure out what has happened. I verified the top speed on a GPS and it is correct. I also put the old 23 pitch back on, and got the exact same results. It is like I am only getting 75% of the power I should be.
The boat is 3800 lbs dry weight and 22’ 9” long. With 415 hp I’m not happy.
Again, I am new to all of this, and would appreciate any advice.
Does anyone have any suggestions for my need for speed?
I guess I just expected a lot better top speed.
I am willing to spend $1k -3k.

Headers? Msd Ignition? Blackhawk? jasonljohnson at alltel.net

MACDAD260

It's possible that you were on the rev limiter with the 23" miarge prop. The rev limit should be higher than 4900 rpm, though. The 25" Yamaha prop sounds like the ticket. That speed seems reasonable for your rig.

Now for the bad news. You may have damaged the engine when it over heated. Some pistons could have started to seize and stuck the rings. Or, you could have blown the head gaskets which will cause low performance, too. If you did nothing other than change the impeller then it must be an engine problem. Do a compression check. If any cylinders are less than 150 lbs you may have a problem. Sorry. Look on the bright side. You just might get to spend that 1K-3K sooner than you think. Good luck.

Excalibur502mag

Thanks for the info Macdad.
I have not checked the compression yet. However, I have come to the strange conclusion that 25 is just too high of pitch for the overall diameter. Again, I will say that I am knew to this and learning it all the hard way.
Good news is the strange part. I tried going the other way on pitch for the heck of it, and found good results. I tried a friends stainless mirage 21 pitch three blade, (same diameter) and just an hour ago got 66 mph (not gps). Unbelievable whole shot and 5000 rpm. I guess my misconception has wasted me a lot of time again.
Next question(s).
I have looked into the Hydromotive props and heard a lot of good things about the 4 blades. However, like everyone else, I do not want to go spend a bunch for a new one if I don't know which one I need. I am in Lincoln, NE and can't find a prop in town over a 21 pitch.
I am very familiar with ebay and could pick one up on their. Any ideas?
Secondly, after reading as many threads as possible about my engine, I went out and bought a new set of NGK BR6FS plugs. Can anyone confirm this is the best choice and give me the proper gap?

Thanks in advance for all the help.

russ

Did you do a search here an on speedwake to see what other people are using with your boat. You can work with Houston Prop or Throttle up. I think they both have test programs.

Just my opinion but the speed sounds low for that HP and size boat. I would think you should be able to spin a 23 Mirage Plus prop to 5000 RPM's and 65+ MPH. It might be a good idea to get it into a honest mech. to get the motor checked out.

Excalibur502mag

Thanks Russ,
I can check the compression and plugs tommorow, but I don't think there is anything wrong with the motor.
I can't say that there is a very knowledgable 502 mag mechanic in this town. When I asked them a question about plugs they acted like they had never heard of it. He asked, "Is it like a 454?"
Shouldn't a Mercruiser Mechanic be able to hook it up to a computer?

russ

Yea If you can get a Mech in the boat when your running it or just running on the hose he can hook a scan tool up to it to see if it's spitting out any codes. Also might want them to check the timing while he's at it.

Excalibur502mag

Still looking for advice on the best plugs

Will I be ok with the NGK BR6FS?

MACDAD260

If those NGK plugs are recommended for a 502 then they will work fine. In my opinion, some plugs may be a little better than others but you will gain very little by just changing plugs, no matter what kind you put in. I have tried AC MR43T, AC R43TS, an NGK pug that I can't remember the number of and I am currently running Champion RV15YC4 and am having good luck with those, too.

As a point of reference for you I have a Baja 260 which is a little longer and heavier (dry weight 4500 lbs) than your Excalibur but it does have a 21 degree deadrise hull, same as yours. Overall, very similiar boats. I have a carb 502 and with a 24" Bravo 1 four blade prop my best speed is 64.5 on GPS at about 5200 rpms. With the right prop on your lighter boat you should be in the high 60's if your engine is running right. Get a mechanic to check out the motor for you and yes, it is "like a 454". If he can work on a 454 he can work on a 502. Good luck.