Minnesota Classic Glastron Forum

General Category => Members Profiles / Introductions => Topic started by: Tapani on August 12, 2021, 08:34:13 AM

Title: Greetings from Finland
Post by: Tapani on August 12, 2021, 08:34:13 AM
Hello all and greetings from Finland !

Bought my very first motor boat about a month ago - a Jurmo Trimaran from 1971.

Since the boat has - a rather rare thing over here - a cathedral hull and the Finnish manufacturer Tradex had close relations to Glastron at the time I thought I register and join you.

Production started in 1971 as "Tradex Trimaran" with both a HT and a BR version on sale. Even the Finnish president back then, Urho Kekkonen, had a BR to boat guests around his summer residence. Tradex manufactured 15 and 16 foot Glastron boats over here under license at the turn of the -60's to the -70's, haven't been able to find out which models they were..... and discussed the possibilities to produce the Swinger too, but the license costs became too much.

Anyway, I believe my boat was sold in 1971 with a Chrysler 70 hp OB, but never got registered. The last time before first registration in 2018 the hull touched water was early -80's and boat was stored until the owner passed away. At the time it had a 115 V4 2 stroke engine, which didn't run. The person from whom I bought it from swapped the engine to a 80hp four stroke Efi Mercury from 2008, which is quite heavy for the boat, I believe.

But since the boat has not been used much at all during it's life of 50 years it's in rather good condition, I think.

Many things do need attention, but that's part of the deal. For example, I believe the engine sits too low - the bow is very high prior to planing, the ventilation plate runs well under the water at speed, feather spray from the engine too and the boat porpoises quite annoyingly if not fully trimmed down. Loading the bow with a few sand bags helps the slow running position, but not the porpoising at speed.

Let's discuss those items if some you is interested.

A couple of photos attached  8)

Kindest regards from Finland,

Tapani
Title: Re: Greetings from Finland
Post by: Hyperacme on August 12, 2021, 10:44:45 AM
Welcome to the forum Tapani !

There's a short Glastron history here ..
http://www.classicglastron.com/gl-reflt-index.htm

Can you post some pictures of your stern/transom/motor/set up ?
Title: Re: Greetings from Finland
Post by: dorelse on August 12, 2021, 11:03:37 AM
Welcome!!!
Title: Re: Greetings from Finland
Post by: Tapani on August 12, 2021, 01:21:20 PM
Thanks for the replies and welcome  :D

Unfortunately this the only one I have. The AV plate is right at the level of the "keel".

I have a 9 sec video too, but it's too big a file to post.

A few frames - 20 knots speed.

/Tapani
Title: Re: Greetings from Finland
Post by: Tapani on August 12, 2021, 01:22:28 PM
A few more frames

/T
Title: Re: Greetings from Finland
Post by: Tapani on August 12, 2021, 01:23:27 PM
And the last one

Title: Re: Greetings from Finland
Post by: Hyperacme on August 12, 2021, 02:43:36 PM
Looks like a long shaft motor and at level with keel should be good.
New Merc's in the 75 to 115 HP range are about 360 lbs. so not to heavy compared to older inline 6's and V4's which were about 300 to 350 lbs. range.
 https://www.mercurymarine.com/en/us/engines/outboard/fourstroke/75-150hp/

I don't know ..
Sorry if this is dumb questions .. but ..

Have you pulled drain plug and tilted front of boat up as high as it will go .. make sure there's no water in hull under floor ?

Do you have a very large fuel tank and more then one battery in stern ?

Maybe motor is to high and not to low ?

How fast is max speed ?

Title: Re: Greetings from Finland
Post by: Tapani on August 12, 2021, 10:51:38 PM
Thanks for your reply.

I have an electric pump to empty the hull, not much water there.

Just one battery at the stern, two fuel tanks, 12 gallons in total. One empty last time we tried.

Top speed 33 knots @5700 rpm roughly.... only few seconds to planing. Trimming would raise the rpms.... too high I guess? Should I try another prop first? Maybe a High5? I don't mind loosing a bit speed.

As an absolute beginner: is the motor height setting different with this type of ahull from the norm? Manufacturers recommendatio is spot on with the Merc.

Tapani
Title: Re: Greetings from Finland
Post by: Hyperacme on August 12, 2021, 11:14:37 PM
33 Knots equals 38 MPH .. which seems pretty good if it's a GPS reading, old pitot tube speedo's can be off.
Your max RPM's as per Merc is 5800 RPM's.

What pitch / brand of prop are you using ?

 
Title: Re: Greetings from Finland
Post by: Tapani on August 13, 2021, 02:00:13 AM
Hello,

Yes, GPS reading.

First time I checked..... its 854360A45P16 Mercury, so it's a 13.25x16.

Hmmm...... A lot easier to swap the prop to a higher pitch than raise the engine.

Attached is lower boat weight part of the prop table from the factory manual.

For an 18 foot 1800 lbs boat (pay load included) I'd look at a 13.25x20 Laser II, a 12.75x20 Hi5 or a 13.75x19 Trophy.

Most of what we expect to do is two persons, 20-25 knot cruising. And naturally try to get rid of the porpoising and reduce nose lift during hole shot.

As it is now it porpoises almost dangerously (with even a touch of trim from the very low position), massive bow lift during hole shot, it's difficult to steer at speed, pulls to the right and when releasing the throttle it veers strongly to the left.

Any comments and ideas are greatly appreciated.

/Tapani
Title: Re: Greetings from Finland
Post by: Hyperacme on August 13, 2021, 02:23:53 PM
Maybe try a few different props
If that doesn’t work maybe try a whale tail
One of those fin things that are attached to your cavitation plate
Some people say they work
Might be worth a try if all else fails
Title: Re: Greetings from Finland
Post by: Tapani on August 16, 2021, 07:35:03 AM
Hello again,

I found another similar boat with a Honda 90 motor, which sits quite significantly higher than mine - see photo.

I talked to owner and his top speed with four adults and 100 litres of gas in a stainless steel stern tank is 38 knots. He can also make to boat porpoise by trimming the engine up, way up from the 0-position and it will calm down by just tapping the trim a touch down. I can't run anything above max negative.

I will need to drill new lower holes, make an aluminum plate behind and also in front of the transom to beef if up and cover the wrongly drilled holes and the install the engine 2-3 holes higher. This won't happen until next week when I go home from the lake.

After I get this sorted I will address the prop issue.

Tapani
Title: Re: Greetings from Finland
Post by: Hyperacme on August 16, 2021, 10:04:26 AM
A motor to high or to low will porpoise ...

Doesn't your motor have a few mounting holes on bracket ?
You could try them first before drilling new holes.

I would epoxy wood dowels into old motor mount holes then cover with gel or Marine-Tex or something to seal holes.
 
Title: Re: Greetings from Finland
Post by: Tapani on August 16, 2021, 10:36:55 AM
Thanks, yeah it does. Sort of.

The lower ons are not drilled correctly to similar positions as the upper ones. The are much farther than 8". Only on hole can be raised - there's also an aluminum trim on the edge on the transom, adding a plate will be enough for the motor to clear that.

Thanks,

Tapani
Title: Re: Greetings from Finland
Post by: Hyperacme on August 16, 2021, 01:34:04 PM
I used "CMC Transom Wedges" to get clearance for aluminum trim and so my splash well drain would drain better.

CMC Transom Wedges
https://thmarinesupplies.com/collections/cmc-marine-products/products/cmc-transom-wedges-2-degree
Title: Re: Greetings from Finland
Post by: Tapani on August 16, 2021, 01:46:22 PM
Great, something like that, but with even thickness for ease of making.

👍

Tapani
Title: Re: Greetings from Finland
Post by: thewillets on October 22, 2021, 09:12:18 AM
Are you sure that the motor is tilting far enough toward the transom ?

It sounds like the motor when pulled all the way "in" is still to far "out" if you get my meaning.

I met a first timer with an older boat last summer who had a similar problem and his motor had a pin that set how close the motor would tilt toward the transom.  I am not an expert in outboards but I got to looking at the angle and after a bit of puzzling it over I found that pin and moved it 1 hole closer to the transom.

He took the boat out and it made a huge difference.  Just a thought, there are people on this forum much more knowledgeable than me !
Title: Re: Greetings from Finland
Post by: Tapani on June 06, 2022, 06:08:35 AM
Greetings again from Finland !
 
I know it's been a while, but I've finally got progress with the Jurmo Trimaran 😊

Last summer, I experienced quite a bit porpoising and trimming problems. Now these are pretty much solved ? at least to an acceptable level.

I raised the motor in total three holes and now the anti-ventilation plates sits 1" above the keel line. I had a 10mm thick aluminum plate made to support the transom. I also tried two new props and now I'm running a four bladed Trophy Plus 13 3/4" diameter and 17 pitch. With only two holes up last summer I maxed out 5950rpm and app 33 knots.

I de-restricted the motor to the full 100hp by removing the orifice and remapping the ECU. Now with the motor one more hole higher I just run into the limiter (6120rpm) at 34 knots with two persons and 35 knots alone. The hole shot is the best thing of all, the engine's characteristics improved dramatically. I installed also Vesselview Mobile and a cooling system pressure gauge for some peace of. I will run this prop at least for the summer ? no need to go any faster with a 52 year old boat, best cruise is 21 knots anyways. Fuel consumption is around 3-3,5 us gallons an hour at that speed.

I also re-did totally the electrics and relocated the battery to the front. Further, I replaced the Hydrodrive 90 steering with a Baystar and it made a huge improvement. New bilge pump plumbing, improved lights, swimming ladders and some grabrails and an electric winch for the trailer completed my winter efforts.

Kindest regards,

Tapani
Title: Re: Greetings from Finland
Post by: Plugcheck on June 06, 2022, 08:29:45 AM
The prop you're now running is providing stern lift, it's what I use to solve very similar issues on a V-8 IO Glastron.    It's amazing how small changes can have such big effects
Title: Re: Greetings from Finland
Post by: Hyperacme on June 06, 2022, 02:58:52 PM
35 knots = 40 MPH
Sound like you got everything sorted out ..
Title: Re: Greetings from Finland
Post by: Tapani on June 28, 2022, 11:47:09 AM
Hello again,

The more I run the boat the better it feels 👍.

Any idea of the peak torque rpm level of my motor?

I tried a few holeshot runs and from stand still and the revs raise to app 4500 at wot and stay there until more speed is picked up.

The acceleration feature in the Vesselview shows a rather constant 5.8-5.9 sec to 30 MPH. Feels good and quick enough, ambient temp 31C, water 21C.

I don't mind hitting the rev limiter at full power, no need to go that fast, really.

Kind regards from Finland,

Tapani
Title: Re: Greetings from Finland
Post by: Hyperacme on June 28, 2022, 06:01:00 PM
2008 Mercury 80 HP EFI spec's
Title: Re: Greetings from Finland
Post by: Tapani on July 13, 2022, 01:54:47 PM
Hello again,

Still trying to figure out and learn what affects what....

The distance from the transom/keel edge to the vertical plane at the center of prop blade roots is 56cm @ 0 trim (antiventilatio plate aligned with keel line).

Is this a lot? Compared to the 2 strokes of the early -70's?

The antiventilation plate is now 3/4" above the keel line, but is still under water at planing speeds.

Tapani
Title: Re: Greetings from Finland
Post by: Hyperacme on July 13, 2022, 03:15:08 PM
All motors (20 inch shaft or long shaft)  from 70's until now are the same as far as shaft length, only difference is where it's mounted on transom.
I'm not sure how much your boat weighs but 40 MPH / 35 knots sound pretty good.
You could try a jack plate to fine tune .. but would cost a lot for small MPH/knots increase.
If you start to lift it a lot, you should get a PSI gauge so you know your getting good water pressure to motor at full speed.
It's hard to say what's your best set up .. Just keep testing until your happy ...
 
Title: Re: Greetings from Finland
Post by: Plugcheck on July 13, 2022, 07:43:25 PM
I'd just like to add that folks spend considerable time, money, and effort finding what works best for their application.    As Gregg mentioned, as long as you have good water pressure, you can go higher.   It all depends on what you wish to accomplish, some it's longevity, some it's top speed, others it's yank multiple skiers up.   Enjoy the hobby, report your findings, and always pictures are welcome.
Title: Re: Greetings from Finland
Post by: Tapani on July 13, 2022, 09:42:48 PM
Thanks guys for your replies.

I have a pressure gauge for the cooling and it shows good numbers, over 20 psi at full speed, no fluctuation.

The distance I meant is in the prop shaft axial direction. To the rear from the transom, how far aft is the prop from the transom. If I understood correctly the water level rises an inch for every 8-10 inch.

My aim is to be able to trim to "0" at cruising speeds, 21-27 knots, without porpoising. This is not yet quite possible even with just me onboard.

I am trying to think about everything before installibg trim plates.

When the lake calms I'll take a few photos of the av plate at different speeds.

Tapani
Title: Re: Greetings from Finland
Post by: Hyperacme on July 13, 2022, 11:01:25 PM
Not sure how "Setback" would affect your boat.
I think your right about the farther back you go the deeper the drive would be, But don't know for sure ..
I think setback would work with a very light boat with high HP.
Title: Re: Greetings from Finland
Post by: Hyperacme on July 13, 2022, 11:12:44 PM
Doug has a light boat ( C500 about 700 lbs / 317 kg. ) with a 200 HP Johnson and 12 inches / 300 mm of setback.
He say's he's having  proposing problem and is going to remove 6 inches /  150 mm of setback.
Title: Re: Greetings from Finland
Post by: Tapani on July 13, 2022, 11:37:02 PM
Hi,

Thanks for your reply.

I am not able to paste a linkhwre, but search for "Boost Speed with Outboard Engine Height Adjustments". And check "other variables".

I got the impression that motors have hugely different dimensions. And the lower end of the period 2 strokes look small compared to my motor.

My boat shell alone is roughly 500kg.

Kind regards,

Tapani

-edit: No, I am not looking to install "a set back", but thinking if I should still lift the motor further up .
Title: Re: Greetings from Finland
Post by: Hyperacme on July 14, 2022, 11:07:15 AM
Your boat/motor, gas, battery, etc. without you in the boat, comes to about 1600 lbs. / 725 kg.
I had a V156 with a 60 HP Johnson, gas, battery, etc. without me in the boat it came to about 1000 lbs. /  450 kg.
I was getting about 40 MPH/GPS / 64 kh.
On another boat if I added a 200 lbs. / 90 kg. passenger, I would lose up to 3 MPH / 5 kh.

You could be right about newer motor size, as the newest motor I owned was from the late 1980's.
I know Merc makes motor that are "High thrust" for pontoon's and heavy slow boats, maybe with larger lower units and lower gearing to swing larger props.

Are you still having  proposing problem ?
Title: Re: Greetings from Finland
Post by: Tapani on July 14, 2022, 12:13:13 PM
Well, yes and no

I can always stay away from porpoising by trimming down. Having said that, it's clear that the motor would like to be trimmed higher under almost all conditions - except full 35 knots. It always gains rpm by trimming slightly up, and starts porpoising.

My main goal is to reach neutral "0" trim at cruise speeds.

If trimmed to "0" it will not ventilate if I open the throttle fully from stand still. But will porpoise soon after I reach planing speeds.

It's quite windy with big waves still, I will take a few photos of the av plate when the lake calms down

Tapani

-edit: I thunk the total weight is a bit more with all the gear I carry, tools, anchor etc. With four large adults the porpoising is much worse and less trim can be tolerated. But that's where the torque and the 4-bladed prop shine. Hole shot is still good  and 30+ knots easily reached (hits the limiter alone). I do not need any more speed
Title: Re: Greetings from Finland
Post by: Tapani on July 15, 2022, 12:18:35 PM
Hello again,

I went for a spin - 200m from home got stopped by the police, they checked my life vest, fire extinguisher and I had to blow in the alcometwr thing 🤗🍻. First time we've ever seen them here. Friday evening, some jetskis buzzing around so I guess it's good 👍.

I dis aeound 30 knots and took a few photos of av plate. I guess it's very close to the watwr surface, but still under it.

What do you guys think?

Tapani
Title: Re: Greetings from Finland
Post by: Tapani on July 15, 2022, 12:26:37 PM
Bad choice of photos, the first one.

T
Title: Re: Greetings from Finland
Post by: Hyperacme on July 15, 2022, 01:50:31 PM
BWI's (boating while intoxicated) have been in effect in Minnesota for over fifteen years now, not sure if everyone gets a breathalyzer/test or just persons who seem intoxicated ..
Set up is a compromise .. all depends on what you want. 
Title: Re: Greetings from Finland
Post by: thewillets on August 04, 2022, 10:40:55 PM
That is great to hear, you have breathed new life int your classic.
Title: Re: Greetings from Finland
Post by: Tapani on August 12, 2022, 11:49:36 PM
Thanks for your comments.

As explained, I raised the motor one more hole up. It sits now a full 3" higher than when I bought it. AV-plate 1,5" above keel line.

A huge improvement 👍

Check out hole shot recorded with my new GoPro 🙈.

https://youtu.be/dlW1JTXZBG8

It's actually 0-35 knots, you can just hear the motor run against the limiter.

I can induce porpoising at cruise speeds by trimming the motor up.

https://youtu.be/3KfsJME6IZY

But it runs real sweet at full song, just keeping the revs at 6000 and thus below limiter. I have a cooling water pressure gauge - steady 25 psi at full speed.

https://youtu.be/xdY8XMSIK-U

I need a lot more seat time before I can tell you more.

Kind regards,

Tapani