5.7l carbed RPM question
 

I am really enjoying my 'new to me' 198 Shabah. I do have a couple of questions about the throttle and rpm's. I have the meruiser 1997 carbed 5.7L with an Alpha 1 drive and a 19p three blade prop. The boat drives fine, but at WOT it is only turning between 3900 and 4k rpm. It drives to that mark fine and will hold that all day without even breaking a sweat. It just feels like it should have more to it. The engine isn't working hard at all and it doesn't matter where I have it trimmed at it won't break 45 mph. I checked the throttle cable and it pulls the throttle all the way to the stop.
If I put the boat in nutral and rev it up, it acts like it is hitting a rev limiter right before 4k. If I ease the throttle slowly it will go up to about 4300 rpm before it stops. I would think that with a 19p prop I should be reving quite high, but it just never gets there.
The other problem I have is if I drive around for a while and then park for a half hour or so, it is hard to start. I have to put it in nutral and pump the throttle to get it to start. Then it runs just fine again. My last two boats were fuel injected, so I've never had to deal with carb issues before.
I am trying to run out the fuel that was in it that was combined with some premium fuel that I added when I first got it. I don't know how old the fuel is so I am trying to run it empty before I add any new fuel. I also am planning on changing the plugs and wires to see if that helps, but beyond that I don't know what to do.
Any help would be appreciated.

Re: 5.7l carbed RPM question
 

I have a new to me 1990 2000xl with the 5.7L and alpha one. I am running a four blade prop (don't know the pitch) and I am getting 45 MPH at 4500 RPM at WOT. I would think you are not turning enought RPM's with your 5.7L, or maybe I'm turning to much.

I'm still learning, so take my information for what it is worth.

RVS

Re: 5.7l carbed RPM question
 

What's the gear ration in the outdrive? If it has steeper gears it can make your 19P behave more like a 21. I'm currently fighting a similar problem. My 5.7 only hits 4475 RPMs WOT at 52 MPH. That motor should be hitting 4800ish. My 1.47 drive ratio makes a difference. If I dropped to 19P I'd get more rev but no more top end.

Also, what diameter is your prop? if the diameter is too big you'll also have a similar problem. Last, is what elevation you running at? The hard start could be a sign of running a little on the rich side.

Re: 5.7l carbed RPM question
 

Thanks for the input Stereoman, I am having similar issues with the 5.0, starting and RPMs. I think part of my issue is the elevation, I'm at about 5,000 ft. How would I go about adjusting the carb if I'm running rich. It starts pretty hard the first time out and then after that it starts fine. Any advice would be greatly appreciated. Kitto

Re: 5.7l carbed RPM question
 

I'm not sure of the gearing yet. I will check when I get a chance. Even if it is geared tall I would think that the hole shot would be weak and it isn't. I took it up yesterday and it still tops out at 3900 rpm @ 45mph, of course I haven't changed anything so I didn't expect any differences.

As for the hard starting. When we were wakeboarding it started up just fine everytime I shut it off and restarted, and it ran great. However each ime we parked for more than 20 minutes I had to pump the throttle in nuetral to get it started again.

Re: 5.7l carbed RPM question
 

I will be taking my 90 2000XL out tommrow and will note back what I am getting out of it. I checked my prop and it is a four blade 19P but what I think is cupped. I'm sure I am getting 45-47 mph at 4,500 RPM.

3900 RPM seems low for your engine, should be around 4300-4600 rpm at WOT (check what is noted on the top carb cover, should have WOT RPM range, SN#, Spark Plug Gap, ETC).

Is your throttle cable adjusted short and not letting the carbs open all the way up? Not sure how you would check this or if it is even possible, but from what you are saying, its not bogging down, just not turning high RPM's

RVS

Re: 5.7l carbed RPM question
 

My motor indicated the WOT is 4200 - 4600. I have a four blade stainless steel prop with a cupped 19 pitch.

Yeasterday with a full load of fuel, the family and all our stuff, I was running at 4600 rpm and 49 mph by the tack and speedo on the boat.

Hope you can findout your issue.

RVS