5.7 TBI perfomance issue on a rebuild 14.5x17 prop

[zero lash]

I have a 98 sesearay 210. I had bought it with a cracked block and put a rebuilt motor in it was bored 30 over and i upgraded piston in rings to get alittle more compession. I also installed a thru-hull exhaust from the side.
I have set the timing at 10 % BTDC and it idles fine my top speed is about 32 mph at about 4500 rpm. with a half a tank and 5 adults. i am not sure what is going on. It idles fine but i can tell its off.

 

[series60]

Re: 5.7 TBI perfomance issue on a rebuild 14.5x17 prop

It that speedometer speed or GPS speed?

 

[Don S]

Re: 5.7 TBI perfomance issue on a rebuild 14.5x17 prop

It idles fine but i can tell its off.

It can't do both, does it idle fine or is it off. And what do you mean by off? A little rough at idle could indicate having a couple plug wires crossed. Are you sure you have the valves adjusted properly. We get a lot of problems with valve adjustments in the forums after an engine is rebuilt.
You say you get 4500 rpm at WOT, what was it before you rebuilt the engine?

 

[zero lash]

Re: 5.7 TBI perfomance issue on a rebuild 14.5x17 prop

I had a reputable machine shop do the rebuild I would hope they adjusted everything correct. I bought the boat with a cracked block so I never ran it before. I was told by the owner it ran around 4500 to 4800 WOT. I set the timing to 10 degrees and when I did so it did not idle well. So I disconnected the timing tool and gun and disconnected the IAS and plugged it back in and it idled fine after that. I mean off as its only getting 30 mph from the speedometer and should be much more.

 

[QC]

Re: 5.7 TBI perfomance issue on a rebuild 14.5x17 prop

Need to verify speed by GPS. Previous owner was getting 4500+ and now you get 4500 . . . Same prop? Also, your TBI is setup for the old iron. How different is the new iron?

I find a 1.47 ratio and with the data you have supplied I get 35% slip. Tach and/or speedo are off. With 15% slip plugged in I find 42 MPH if tach is right. How was hole shot? If hole shot was good, I suspect speedo. If hole shot was really poor, I suspect Tach is reading high. Could be either or both, and could also be a totally cruddy propeller, and of course the engine could be sucking too. Or you could have a little, or a lot, of all four.

 

[TilliamWe]

Re: 5.7 TBI perfomance issue on a rebuild 14.5x17 prop

Speedos are notoriously inaccurate, so you can't judge by that. Tach in boats go bad too, so you might not be able to trust that reading, either.

 

[zero lash]

Re: 5.7 TBI perfomance issue on a rebuild 14.5x17 prop

I could believe that the speedo and tach could be off but not by 2000 rpm. I am a pretty good guess of water speed and I have been on boats that run 50-80 mph on water. If the timing is off 2-5 degrees could that make alot of difference?

 

[QC]

Re: 5.7 TBI perfomance issue on a rebuild 14.5x17 prop

Where'd you get 2000 RPM? I actually think it's probably running around 42 MPH and the RPM may be right.

Regardless of the engine, sumpin' ain't right with the speed and RPM info Need that right first to make any good assessments about anything else . . .

 

[zero lash]

Re: 5.7 TBI perfomance issue on a rebuild 14.5x17 prop

Hole shot is fair to poor it has a SS prop that is next to excellent condition. When I set the timing I brought it too 1800 rpm and set it. When doing so the rpms jumped around.

 

[Don S]

Re: 5.7 TBI perfomance issue on a rebuild 14.5x17 prop

You don't have a prop problem at this point. If you can't turn more than 4500 rpm with a 17" pitched prop on a 21' boat, then you have either a really heavy boat, dirty bottom, or not trimmed right.
If those items are all ok, then you have engine problems of some sort. The first thing you have to do is make sure the obvious things like timing are where they should be. Verify the tach is accurate. Have you hooked it up to a diagnostic scan tool? That will tell you your rpm.

 

[zero lash]

Re: 5.7 TBI perfomance issue on a rebuild 14.5x17 prop

No I haven't hooked up a scan tool. I don't have one. Here is a thought hopefully not too off topic but, if my bilge and float are attached through the hull and water got in the boat and in the holes made from the pump where and how does that water get out. The reason I asked is the previous owner had in a slip and did not have shore power and the battery went dead and had filled up past the starter with water and when I removed the motor I replaced the pump. When I removed the screws for the pump water came out from the holes.

 

[thumpar]

Re: 5.7 TBI perfomance issue on a rebuild 14.5x17 prop

You need to find out how fast you are really going before you know if there is a problem or not. Most cell phones have a GPS anymore so it should be easy to do. If it really is slow then water logged foam could explain it. You can find a scale to see how much it weighs and compare it to normal.

 

[Don S]

Re: 5.7 TBI perfomance issue on a rebuild 14.5x17 prop

There should be "limber holes" in the stringers and bulkheads to allow water to drain from forward aft, and from the sides into the bilge so water can drain.

 

[QC]

Re: 5.7 TBI perfomance issue on a rebuild 14.5x17 prop

When I removed the screws for the pump water came out from the holes.

I believe you are saying the mounting holes, into the hull, for the bilge pump. If so, not good. Could indicate a number of issues including a soaked hull, and possibly (probably) soaked foam. This could explain the weight. Where'd you get the 17 inch pitch prop? Previous owner?

Edit: Please confirm if the holes were into the bottom. I think he is saying water came out of the holes which were mounted into the hull. I don't believe the limber holes will help that

 

[zero lash]

Re: 5.7 TBI perfomance issue on a rebuild 14.5x17 prop

Yes if that's an issue. How can I get it out? That might be an issue but when I got the boat in the water the first it ran good except it did not idle so I change the idle air control and set the timing from then on it idles fine but does not perform well

 

[QC]

Re: 5.7 TBI perfomance issue on a rebuild 14.5x17 prop

I think you need to start with the tach and speedo verification. Then we'll know more. Please reread everything here and get us as much info as possible. Mo info = mo betta answers

If the hull and foam are soaked, you have some big repairs to consider. Let's get other stuff sorted first, and then we'll move down the list. Good luck! We'll hang with you, just answer each question, there is always a reason we ask

 

[Tail_Gunner]

Re: 5.7 TBI perfomance issue on a rebuild 14.5x17 prop

Apparently this is a TBI motor Explain how you set the timing to 10. There is a very spefic way to do so. Did you short the ecm. Might want to post the ecm model number and ignition type

 

[zero lash]

Re: 5.7 TBI perfomance issue on a rebuild 14.5x17 prop

I borrowed a tool to set it into service mode. But first I got the boat 2 operating temperature. Plugged in the tool. Plugged in the timing gun. Manually set The throttle to 1800 RPM. Then I set the timing to 10 degrees Before top dead center. It took a few times because it kept stalling In RP M's kept dropping Or rising.

 

[Don S]

Re: 5.7 TBI perfomance issue on a rebuild 14.5x17 prop

Why did you use 10? BTDC? Manual calls for 8?. Do you have the Mercruiser serial number for your original engine? Do you have the Thunderbolt V ignition or the Delco EST? Is it MEFI 1,2 or 3.

 

[Bondo]

Re: 5.7 TBI perfomance issue on a rebuild 14.5x17 prop

Hole shot is fair to poor it has a SS prop that is next to excellent condition.

When I set the timing I brought it too 1800 rpm and set it. When doing so the rpms jumped around.

Huh,...??? You set the timing, at 10? btc, at 1800 rpms,..??