Oh boats... Supra has a low speed missfire

OVERKILL

$100 Site Donor 2021
Joined
Apr 28, 2008
Messages
52,194
Location
Ontario, Canada
I expect it'll be a cracked plug.

As per the other thread, the engine and drive were out for the fibreglass work to be done. Since being back together it has a missfire (it did not previously) so I'm thinking a plug got bumped and cracked during the removal or install. I pulled #1 and it looked decent so I know it isn't that the plugs are old or in horrible condition.

EEC-IV can run a cylinder balance test, but I don't think I need to go down that rabbit hole with it yet, I'll probably toss a set of plugs into it this weekend as a start. The boat did sit for 5 years prior to us picking it up, but given that it wasn't missing the first season we were out in it I'm not inclined toward an injector issue.

Injector harness looks fine, plug wires look fine (but are OE, so they are old). Cap and rotor are decent.

Also may have to do some hunting for a leak, it's taking on a bit of water still and it isn't the prop seal. Possible areas of ingress are:
- stabilizer fins along the centre of the hull
- rudder
- exhaust

Nothing is obvious, the leak isn't substantial.

I'll be back up at the lake the end of the week (just got home) so hopefully can get this cleared-up.

UNADJUSTEDNONRAW_thumb_130b.jpg
 
Joined
Dec 5, 2003
Messages
2,702
Location
New England, USA
Leaks are surprisingly hard to locate sometimes, Boat Life Caulk is your friend. Finicky to use, but great when done right. Learned that the hard way.

You probably know this but, regarding the turn fins and rudder, enlist a friend to try and look at them loaded, in a hard turn. That's how we found our rudder port leak and how I discovered the prior owner's 'mechanic' or someone had tried to seal it with red RTV...

Love that boat BTW
 

OVERKILL

$100 Site Donor 2021
Thread starter
Joined
Apr 28, 2008
Messages
52,194
Location
Ontario, Canada
Leaks are surprisingly hard to locate sometimes, Boat Life Caulk is your friend. Finicky to use, but great when done right. Learned that the hard way.

You probably know this but, regarding the turn fins and rudder, enlist a friend to try and look at them loaded, in a hard turn. That's how we found our rudder port leak and how I discovered the prior owner's 'mechanic' or someone had tried to seal it with red RTV...

Love that boat BTW

Thanks for the tip! My plan was to just ride it the season and then when it is on the trailer, load the bilge with some water and look for leaks underneath. Good point on the turn fins though... A lot of the fasteners were backed-off when we first got it, I changed out the plain stainless nuts to nylocks.
 
Joined
Dec 5, 2003
Messages
2,702
Location
New England, USA
Thanks for the tip! My plan was to just ride it the season and then when it is on the trailer, load the bilge with some water and look for leaks underneath. Good point on the turn fins though... A lot of the fasteners were backed-off when we first got it, I changed out the plain stainless nuts to nylocks.
We had some weeping at the strut mounting through bolts. Given the alignment is fine and removing the strut is a big job I did not want to pull it figuring we're more likely to do more damage then we would be fixing. Interestingly the area was sealed with some spread rubbery material from the factory. I wound up removing that and, very carefully, cleaning the area then coating it and the nuts and bolts w/ Boat Life. Not a problem since.

The trick w/ BL caulk is it is VERY sensitive to contamination and solvents. I had a bad result the first time around, the sealant lost its grip and was able to be peeled off as one big piece. Had a good chat w/ BL's tech folks and next time around I cleaned, used a wire brush, cleaned again then used brake cleaner and then wiped the area with a dry rag. After that I covered my palm (gloved :) ) in BL and firmly worked a small amount into the surface grain, then followed up w/ a thicker coat. Perfect result..no weeps.
 

OVERKILL

$100 Site Donor 2021
Thread starter
Joined
Apr 28, 2008
Messages
52,194
Location
Ontario, Canada
Picked-up some Motorcraft plugs for it and ordered a bottle of AMSOIL P.i., will be doing the plugs tomorrow, hopefully that clears things up.
 

OVERKILL

$100 Site Donor 2021
Thread starter
Joined
Apr 28, 2008
Messages
52,194
Location
Ontario, Canada
New set of Motorcraft AWSG22 platinum plugs, some Motorcraft dielectric grease on the plug boots and she's back to running properly.

Now, however, she needs a new thermostat. Didn't break much more than a hair over 120F when I took my sister out wakeboarding.... ugh.

UNADJUSTEDNONRAW_thumb_13a7.jpg
 
Joined
Jul 10, 2012
Messages
7,480
Location
South Carolina
Glad it worked out for you. We have a "new to us" 2008 Chaparral that we bought 3 years ago. Boat only had 60 hours on it. Showroom condition. Well I very slowly changed things out, rotor, distributor cap, typical oil changes, boat needed nothing, though the upper VP gear case was just replaced 2 months ago @100 hours, was an issue in the at the time new 2008 Volvo Penta SX-A drives.
Anyway, got it all done... then ...

Went to replace the plugs, well I gave up, the old ones are still in there. (I think they were replaced at some point in the last decade by previous owner because they are NGK )
Here is my problem. Boat runs great, like new, heck now only up to 106 hours. The darn spark plugs wont come out and I am afraid to apply to much force. Because of this maybe I am not applying enough to break them loose because I am afraid of stripping the threads.

SO I left them for now so I dont mess up my summer by breaking a plug or stripping the head. I also soaked them with WD 40 and will keep them soaked all season hoping that helps. They are tapered plugs without the gasket so bolted right into the head with the "V" type non gasket plugs.
I do want to do the thermostat at some point (just because) and gas filter which is one of those "stone" material ones located right on the fuel pump in a really tough spot. I hate those on the fuel pump filters.

Anyway, glad you got yours done and feel free to chime in on any miracle spark plug removal ideas. Never in decades and decades was I so afraid to break a plug or plugs loose. I only tried it with a 3/8s drive and short extension but I felt the "extension" starting to flex and didnt push it any further.
 

OVERKILL

$100 Site Donor 2021
Thread starter
Joined
Apr 28, 2008
Messages
52,194
Location
Ontario, Canada
Glad it worked out for you. We have a "new to us" 2008 Chaparral that we bought 3 years ago. Boat only had 60 hours on it. Showroom condition. Well I very slowly changed things out, rotor, distributor cap, typical oil changes, boat needed nothing, though the upper VP gear case was just replaced 2 months ago @100 hours, was an issue in the at the time new 2008 Volvo Penta SX-A drives.
Anyway, got it all done... then ...

Went to replace the plugs, well I gave up, the old ones are still in there. (I think they were replaced at some point in the last decade by previous owner because they are NGK )
Here is my problem. Boat runs great, like new, heck now only up to 106 hours. The darn spark plugs wont come out and I am afraid to apply to much force. Because of this maybe I am not applying enough to break them loose because I am afraid of stripping the threads.

SO I left them for now so I dont mess up my summer by breaking a plug or stripping the head. I also soaked them with WD 40 and will keep them soaked all season hoping that helps. They are tapered plugs without the gasket so bolted right into the head with the "V" type non gasket plugs.
I do want to do the thermostat at some point (just because) and gas filter which is one of those "stone" material ones located right on the fuel pump in a really tough spot. I hate those on the fuel pump filters.

Anyway, glad you got yours done and feel free to chime in on any miracle spark plug removal ideas. Never in decades and decades was I so afraid to break a plug or plugs loose. I only tried it with a 3/8s drive and short extension but I felt the "extension" starting to flex and didnt push it any further.
Sounds like the same plug style as this old Ford. Due to the exhaust manifolds, I had to use a wrench + plug socket. They all came out easily with a solid whack to the wrench with an open palm. The secret is typically that sharp impact that breaks them free.

WD40 isn't a penetrating lube, so I'd try something more specific for that purpose.

I've never had to use an impact gun on plugs, but have heard of mechanics that have.
 
Joined
Oct 1, 2002
Messages
3,712
Location
North TX
Since you have spent a good amount of moola on the rig I would think plug wires, cap, and rotor would be in order to finish it off. Along with the new spark plugs that should bulletproof the whole ignition system for several seasons. I hope you find the minor leak...very aggravating.
 

OVERKILL

$100 Site Donor 2021
Thread starter
Joined
Apr 28, 2008
Messages
52,194
Location
Ontario, Canada
Since you have spent a good amount of moola on the rig I would think plug wires, cap, and rotor would be in order to finish it off. Along with the new spark plugs that should bulletproof the whole ignition system for several seasons. I hope you find the minor leak...very aggravating.

Yeah, probably put on a set of MSD Superconductor wires and cap/rotor at some point. These parts aren't in bad shape at the moment however, given the low hours on the engine.

Yes, I'm hoping to find the leak as well.
 
Joined
Jul 10, 2012
Messages
7,480
Location
South Carolina
Yeah, probably put on a set of MSD Superconductor wires and cap/rotor at some point. These parts aren't in bad shape at the moment however, given the low hours on the engine.

Yes, I'm hoping to find the leak as well.
Even though our boat had extremely low hours on it when we bought it, it was still a 10 year old boat, so over time I was replacing maintenance items but no rush since it ran so well, so I thought.
You already know I had to replace the upper gear case of the VP SX-A drive but that was a known issue in its first production year of 2008.

Anyway, havent owned a boat with a distributor, since like the beginning of time but I have one on this boat. I had a new OEM cap and rotor sitting in my garage since almost the day I bought the boat but it ran so well, I only decided to replace it this spring 2 years later.

Well, holy crap, what a mess the old one was, it wasn't an OEM (didn't have copper color conductors)
Below is a photo, in all my life I never saw something so bad that still worked. I want to kick myself for not changing it sooner.
I thought, since this was a carburetor boat it was normal to have to let warm up at the launch ramp, just a little bit, well, with the new cap on it, it ALMOST acts like an F/I engine. Give it a minute or two and I put it in gear, no stall. Check out the photo.
20B77A67-85CA-40F7-962C-D5072AAD9134_1_105_c.jpeg
 
Last edited:

OVERKILL

$100 Site Donor 2021
Thread starter
Joined
Apr 28, 2008
Messages
52,194
Location
Ontario, Canada
Even though our boat had extremely low hours on it when we bought it, it was still a 10 year old boat, so over time I was replacing maintenance items but no rush since it ran so well, so I thought.
You already know I had to replace the upper gear case of the VP SX-A drive but that was a known issue in its first production year of 2008.

Anyway, havent owned a boat with a distributor, since like the beginning of time but I have one on this boat. I had a new OEM cap and rotor sitting in my garage since almost the day I bought the boat but it ran so well, I only decided to replace it this spring 2 years later.

Well, holy crap, what a mess the old one was, it wasn't an OEM (didn't have copper color conductors)
Below is a photo, in all my life I never saw something so bad that still worked. I want to kick myself for not changing it sooner.
I thought, since this was a carburetor boat it was normal to have to let warm up at the launch ramp, just a little bit, well, with the new cap on it, it ALMOST acts like an F/I engine. Give it a minute or two and I put it in gear, no stall. Check out the photo. View attachment 66075
Yikes! That's ugly!

I've been into ours already and checked the condition, they look decent enough (they are OE Ford). The EEC-IV TFI ignition is a pretty powerful system, so it's quite tolerant of these things not being in the best of shape anyways. I have a MSD cap and rotor here I think already, but I sold the FMS 9mm wires I had kicking around for the Capri, so I'll need to order new wires.

Amusingly, the wires on the engine are clearly the grey OE Ford wires that you'd find in a similar vintage Ford car or truck, but they say "PCM" on them ;)
 

OVERKILL

$100 Site Donor 2021
Thread starter
Joined
Apr 28, 2008
Messages
52,194
Location
Ontario, Canada
So, slapped in a standard automotive 180 degree thermostat but the one I pulled out was a Robert Shaw style 160 degree one (I knew it was a 160) so I ordered a proper Robert Shaw style 180 that I'll swap the regular one for the next time I'm up. It got up to 185 and then dropped to 180 and stayed there in use, but the high flow one should be a bit better as when this one was working, it would just go to 160 and sit there, so I expect the same behaviour from the 180.

UNADJUSTEDNONRAW_thumb_13f7.jpg
 
Top