1995 Sport -- temp issues and surging...

8122pbrainard wrote: If you aren't getting enough hot air, tell us how the heater is plumbed. There have been some issues that have been resolved by adding a "Y" fitting.

Sorry, getting a little off topic, but the hot water for the heater comes off a "T" from the temp sensor port just behind the thermostat housing, and the return goes to the bottom of the large elbow below the circulation pump. I found I get the best flow here (I've tried block plugs, etc.).

To increase the circulation, I've installed an in-line hot water circulation pump wired to my heater blower switch. These keeps the water flowing when at idle. I have not used a "y" connector plumbed before the raw water pump intake simply because it means that the thermostat will be open more with cool water flowing in to replace the water flowing out through the "Y" connector. It would also mean a slower warm-up, especially during the winter. Not a bad way to increase flow, but the in line pump (while more expensive than a "Y" connector), doesn't change how much cool water enters the engine. Also, we use the engine on our boats to fill a "hot tub", and of course, that causes a lot of cold water to go through the thermostat to replace what's going into the hot tub. If I used a "Y" connector, I'm already further diluting the temperature of the water. I suppose if I had a shut off valve at the "Y" connector, I could shut that flow while I'm filling the hot tub, and then turn it back on.

Any weeds on the prop? Loose prop shaft coupling? Loose cutless bearing in the strut? Loose prop (bolt)?

I looked at the prop this morning. There are no weeds on it. When I try to wiggle the shaft, there does not appear to be any play in the strut/cutlass bearing. But when I wiggled the prop, there was just a little bit. It has a castle nut with a cotter pin and when I hand checked it, i could move the nut back and forth with my fingers as far as the cotter pin would allow. I assume that is not good and could be contributing to the problem?

How tight should the castle nut be? And do I just pull the pin and put a wrench to it and put the pin back in? Funnily enough, I had the prop serviced last year by the same dealer thta I have been dealing with on this temp gauge issue. It was removed, welded, tuned, and replaced. Hmmm...

On the temp issue, the dealer put a new sender in and said all the wiring and ground checked out ok. It did not install the new gauge that I supplied. No idea why not. But I will install the new gauge and recheck the wiring and grounds this weekend.

I know I keep saying this, but seriously, thanks for all of your help. But for you guys, the dealer would have a lot more of my money.

Jared,
Brian said it all!!! He is correct that the nut tightness does not matter if the prop is on correctly. I have seen many props where the nut was loose or even missing. Read the proper prop installation Brian linked.

Two things I suggest you check for the vibration. Shaft straightness and the condition of your damper. Regrettably the damper needs to be checked by pulling the trans and bell housing. By then, you might as well replace it. They are only about $90 and should be replaced I'd say about every 600 hours. Hour many hours are on you engine? Do you know if the damper has ever been replaced? What boat do you have? If it's a V drive, you may have a different problem.

Jared,
Again, what boat do you have?

scarbs wrote: 1995 Sport Nautique with EFI GT-40.

As long as it's a Sport and not the Super, that rules out a V drive problem creating the vibration.

Jared,
Many here have tackled the damper job with very little mechanical skill levels. It involves disconnecting the prop shaft coupling, the rear trans mounts and loosening the front engine mounts. The two small bottle jacks are placed under the aft end of the exhaust manifolds. They when pumped up will tilt the aft end of the engine up so the bell housing and trans can be removed. The damper is bolted to the flywheel. It's really a pretty simple wrench job. I'd say the R&R can be done in 2 to 3 hours. Less for a mechanic who has done it before. After everything is back in place, then there is the alignment of the engine to the prop shaft. This could take 30 minutes or several hours depending on how much the engine is off. If the alignment is good before you change the damper, then 30 minuets is tops.

How much work have you done on the boat/engine yourself?

Ok, this damper business had me all worried, so (hoping it is the propr, shaft, strut, or cutlass bearing) I went back out to see if I could find any irregularities with any of these items. There just does not appear to be much, if any, movement of the shaft within the strut. But looking closer at the prop, it looks like it may have spilled down the shaft as much as a quarter of an inch. See the picture below. Granted, I do not know what it looked like before, but at some point a prop was definitely about 1/4" farther up the taper. Thoughts?

Thank you. I'll let you know how it goes.

Jared,
It sounds like the key is chewed up. Pulling the prop will tell. Can you tell yet if the prop in fact is off the taper?

The sloppy key really isn't that big of a problem as long as a prop has a decent fit on it taper. Not much torque goes through the key. Most of it is handled by the taper. I think I referenced a drill press in the "proper prop" thread and used them as an analogy. In a drill press, chucks and tapered shank drill bits all use the taper principal for the torque to handle the drilling.

Jared,
Since you have the dial indicator set up, don't forget to check the shaft at the prop taper once the prop is pulled.

Are you going to sent the prop out to a prop rebuilder?

The prop shop confirms that the shaft is straight but the prop is bent. Getting it tuned and should be back in business on Thursday.

Thanks for your help and advice. I will look into getting the damper changed this winter given the hours and my lack of knowledge regarding its history. I may even do it myself, but I'm not very comfortable moving the engine around and then being able to get it back into proper alignment again.

The vibration was resolved when I installed the tuned prop. I found a deal on an ACME 422 shortly afterwards and installed it, and it was even smoother. As for the temp issue, sender, thermostat, and gauge were replaced--the gauge reads 180 degrees when warmed up, but the engine is actually 160 degrees (t-stat is 160 degree t-stat). No one is quite sure why it won't read correctly, but from what I've seen, it is not an uncommon issue.

Afterwards, I had one day ruined at the lake because of a fuel delivery issue. Dealer diagnosed as fuel filter and anti-siphon valve. I replaced them along with the rotor, cap, and wires, and it ran beautifully after.

I then sold the boat to an awesome guy in California a couple of weeks ago and bought a 1999 SAN. So I now I get to enjoy getting to know my new boat. Can't wait.

New boat has the Apex 5.7 in it so I get to learn a new motor. But I have another mechanic who is farther away, knows the GM motors really well. He has all of the correct equipment to plug into the computers of the GM motors and went through it for me before I bought the boat and everything checked out.

He also did a lot of the other work on my old boat but was admittedly not as familiar with the GT-40, which is why I tried the dealer for the temp issue.

I actually assumed it was just a temp gauge before taking it in and bought the temp gauge directly from Nautiqueparts.com and gave it to them to install with a new temp sending unit. At first, they were convinced that there was some other issue with the engine because they could not get the temp dialed in. But after testing and retesting all of the water pumps, examining the plugs, performing a compression, and doing whatever else they did, they concluded that the engine was in fantastic condition and was running at exactly the right temperature. They confirmed this using two different manual gauges and two different infrared guns.

Clearly there was some issue with the sender unit communicating with the gauge, but they insisted that they could not figure it out. But I had already been without the boat for several prime weeks and just wanted it out of there and to get out on the lake with my boys. Other than the filter/anti-siphon issue that I mentioned above, it ran great.

And I of course disclosed all of this to the buyer and provided the invoices for the work so he would know what was going on with it.