Outboard for an Excel Volante 390?

[Steve509926]

Originally Posted by TmMorris

Thanks for that. So the boards could actually be shorter as their only role is to form a rigid barrier against the keel and to spread that force, rather than to locate the floor, which self located by inflation into the join between the tubes and the 'hull'?

Your correct in so much as the keel boards are there to spread the force of the keel over a bigger area on the air deck but it is also spreading the load through the tubes. They still have to be the the right length and shape so as not to deform and press into the hull as you've seen happen in the picture of my SD360.

[Steve509926]

Hi Tim, keel board pics as promised.
That board is 22mm ply and done approx 35 - 40 hrs of mixed use.
In the last two pics you can see that the ply has started to delaminate so it's time to make a new board.
I will probably encapsulate the next board I make in fibreglass, unless anyone else has a better solution.

[pumpkinking]

Originally Posted by Steve509926

Hi Tim, keel board pics as promised.

That board is 22mm ply and done approx 35 - 40 hrs of mixed use.

In the last two pics you can see that the ply has started to delaminate so it's time to make a new board.

I will probably encapsulate the next board I make in fibreglass, unless anyone else has a better solution.

Funny your SD360 keel board is a different shape to the one for my 330, mine is twice as deep?! As in, my board is about 1ft deep from stern to bow, as wide as the floor of course, and about 20mm thick.

[Steve509926]

Originally Posted by pumpkinking

Funny your SD360 keel board is a different shape to the one for my 330, mine is twice as deep?! As in, my board is about 1ft deep from stern to bow, as wide as the floor of course, and about 20mm thick.

Hi PK, I believe your SD330 has one keel board that sits just where the bow tapers in.
My SD360 has two boards (as I think Tim's SD390 has) one where the bow tapers in and one mid way between the bow and the stern.
My SD360 was supplied with carbon fibre boards. The front one works perfectly but the middle one was too thin and would have cut through the hull if I'd left it as it was, so I replaced it with a ply board.
I belive that Excel have done away with the carbon fibre boards and gone back to using ply.

[TmMorris]

Thanks Steve.

My boards are wood, very well encased in a plasticised paint. They are both at least 12" deep bit not as wide as the air deck itself and the edges are simply rounded.

I was initially thinking that they needed to be wider so that they fit into the seams where their job was to help hold the air deck but the earlier post that they exist to form a hard barrier between the sausage keel and the air deck makes sense. In which case, I could fabricate slightly shorter boards that wouldn't touch the hull at all but still form the hard barrier between keel and deck?

My thinking being a honeycomb composite or aluminium plank?

[Steve509926]

Originally Posted by TmMorris

Thanks Steve.

My boards are wood, very well encased in a plasticised paint. They are both at least 12" deep bit not as wide as the air deck itself and the edges are simply rounded.

I was initially thinking that they needed to be wider so that they fit into the seams where their job was to help hold the air deck but the earlier post that they exist to form a hard barrier between the sausage keel and the air deck makes sense. In which case, I could fabricate slightly shorter boards that wouldn't touch the hull at all but still form the hard barrier between keel and deck?

My thinking being a honeycomb composite or aluminium plank?

When you say "wood" do you actually mean a solid piece of wood or ply?
I still think they need to fit far enough under the air deck so that the upward force is supported by the tubes.
The first board I remade was a good 100 mm shorter and there was definitely a more pronounced bulge in the air deck.
I would fabricate one out of ply first to ensure it works well before going to the expense of aluminium or a composite plastic.

[TmMorris]

Decided today was going to be a good day to dust off the outboard and also set up the boat ready for summer.

Having had the plug fouling issue through last season I started by cleaning the plugs, filling the tank with some 100:1 and then firing up the outboard in the bin, dialled back the idle to lean stall and back just over a quarter turn and left it in drive for an hour. I wanted to see what state the plugs would be in after.





Plugs weren't in the perfect state that I would like but certainly better than last season when they were coking up. Only worrying thing was that on restarting it was a little reluctant to idle which was part of the issue last year. What I ended up doing was just raising the tickover a shade. At that point it would start, hope in and out of gear without stalling. Tickover is higher than I'd like but if it helps solve the issue then I'll live with it.

Going to carry plenty of new plugs onboard so that I can just change them as needed should the engine keep fouling as it did.

Boat set up went easily enough. It had spent the winter in the camping trailer.

Have bought the spray hood for this season. It's a remarkably dry boat but I did dunk the bows a couple of times last year which drenched the girls.



Fits easily enough and seems reasonably robust.

I've also moved the fuel tank to the aft. The girls will be forward and have enough mass to compensate and it leaves the bows free for them to be where they want to be rather than having to fit around the tank. We'll soon see if that's an issue anyway.

[TmMorris]

Planning on taking the boat down to Beaulieu at the weekend of the weather is dry. As we'll just be on the river with no plan to go into the Solent I figured I'd lift off the 15 and put the 4 on the boat.

In turn, this got me thinking back to something I'd mulled over last year which was to convert the old Yam 4 to have an external fuel connection as well as the internal.

Originally, the external connector was fitted by Yamaha where the fuel cut off is on the front plate and the internal tank was then absent. Wanting to keep the internal tank I could bring a fuel line through a blanked off plug next to the fuel cut off however, this would mean that the plug would be inboard and I've always found that they leak a little and I don't like the idea of fuel dripping onto the air floor. So I decided to drill a hole through one of the blank plates out the side of the casing.

I'm not usually a fan of doing things like that but it will be easily hidden with a rubber plug if needs be. The main thing is that the fuel connection will be outboard. Using some spare fuel line components I fitted a T piece between the internal tank and the filter and then used two inches of automotive (double skin) fuel line to poke through the sanded hole and fitted a brass fuel connector to the outside.

I thought about fitting the brass connector directly through the casing. This would look neater and also do away with the risk of the rubber line that does go through the hole wearing with vibration and movement but ultimately, I didn't want a hard fixing that would protrude and inevitably get knocked against something when man handling the outboard and possibly cracking the case or doing some damage. By using a bot of hose as the bridge I get some safety against knocks.

I've ordered a few correct parts to do the job properly but plan to test as is at the weekend. It all works fine in the bucket.

[jeffstevens763@g]

Pre mix Two strokes never like idling same oil content as WOT a good rev cleans them up Tim

[TmMorris]

Hi Jeff. Yup. It was the issue last season of the plugs fouling during WOT that has made me a little paranoid.

Pretty sure that issue is resolved on the 15.

One thing I do keep meaning to do is find a manual and establish what the correct actual spark plugs are. I simply replaced like for like last year but obviously it may have had the wrong plugs when I bought it. Getting the correct temp and gap can make a difference.

[jeffstevens763@g]

That would be the issue wrong plugs

[TmMorris]

Yup. Pretty sure I'm using B7HS which every outboard I've had seems to use.

[neil.mccrirrick]

BP8HS in my Mercury 15 [emoji106]

[TmMorris]

Thanks Neil.

My understanding is that for NGK the letter prior to the number is the diameter of the thread so B is 14mm.

The number is the temp where 8 is one cooler than 7.

H is the length of the thread, 12.7mm and S means it's a standard electrode. I'm guessing that changes to letters like P when using a platinum electrode?

So my best guess is that your plug is slightly cooler than mine.

I'm trying to remember the impact of heat differences. I think the hotter the plug the less insulation so less risk of fouling. I think compression plays a part also.

My engine is a 1989 and if yours is notably you get then it may be a more efficient design or a different compression and that allows for a cooler plug?

If my plugs keep fouling then I wonder if moving up one temp to 6 might be worth a try?

[TmMorris]

Ordered a pair of B6hS plugs. One step hotter. Will put them in the toolbox and next time out will swap them in if the plugs foul.

A typical day trip for us would be plodding up the Beaulieu River, dashing over to Cowes and then plodding up the Medina so more time spent pottering just off tickover than at WOT so a slightly hotter plug probably makes sense in that kind of use?

[Fenlander]

TM I forget but is this one of the Yamaha design late 1980s Mariner 15s... if so quite different to the Mercury/Mariners of the mid 90s through to the 2000s most of us think of.

And if it is I have a Clymer manual that covers it.

[neil.mccrirrick]

My understanding is a hotter plug heats the cylinder head faster. Performance engines/high revving engines need a cooler plug.

You may be getting a pre ignition burn with a hotter plug causing a foul

Having said that older engine one plug up or down I wouldn’t think would cause an issue

Sorry I haven’t read all the thread have you done a compression check I’d have been more inclined to think a coked head and partial blocked exhaust port

[TmMorris]

Originally Posted by Fenlander

TM I forget but is this one of the Yamaha design late 1980s Mariner 15s... if so quite different to the Mercury/Mariners of the mid 90s through to the 2000s most of us think of.

And if it is I have a Clymer manual that covers it.

It is. And thanks for the offer. I found a manual today and checked the plugs. 7 is the correct temp. However, if they foul again in use I'm going to have 6s in the box to try as my use doesn't tend to see the engine getting a good thrashing and spending a lot of time not far off idle so on paper a slightly hotter plug is probably a better compromise anyway.

[TmMorris]

Originally Posted by neil.mccrirrick

My understanding is a hotter plug heats the cylinder head faster. Performance engines/high revving engines need a cooler plug.

You may be getting a pre ignition burn with a hotter plug causing a foul

Having said that older engine one plug up or down I wouldn’t think would cause an issue

Sorry I haven’t read all the thread have you done a compression check I’d have been more inclined to think a coked head and partial blocked exhaust port

Thanks Neil. Yup, all checked. I actually think the bulk of the issue last season was a combination of running 50:1 instead of 100:1 and a loose top plate on the carb. It's just a pain in the proverbial to drive two hours for a day out only to discover the issue persists.

[TmMorris]

Lovely day out. Just mucking about on the river. The 4hp Yam is perfect for this sort of stuff.

The external fuel connection worked perfectly. Will tidy it up with proper fittings over the coming weeks.


What I have noticed when cleaning the boat off this evening is that the boards under the air deck don't look like they fit at all properly. They protrude into the hill skin on both sides as if they're too short. I had assumed that they would be sitting in the groove where the hill skin meets the tubes but if anything they look almost two inches too short.

I'll get some pictures tomorrow but I'm assuming this isn't ideal?

The sausage keel has also put a curve in the forward one which probably doesn't help.