Propeller Question

[BaitThrower]

Well I finally took my 3.4m renovation boat out today for the first time on the logan river. Was a bit choppy down closer to aggy sands so turned around and came back.

The Garmin FF140 finder seemed to be perfectly placed giving a very clear image at rest and under power.

The Suzuki DT5, as I suspected, was a little underpowered for the boat and with two adults on board it didnt even come near to getting on the plane :(

Now, the hull is rated for 6HP but I want to put a 9.9HP on at a later stage in hopes it will perform a little better and go against the tide a little better too. But that is outta the budget for now, so my question is... The DT5 at present has an old 2-blade propeller on it. Would it be worth putting on a cheapish aluminium 3 blade propeller? I.e. could I expect maybe a 10-20% performance/speed boost by doing this alone, or am I dreaming? At least I could get a new propeller past the missus, but not a new larger engine at this stage.

[BM]

The 3 blade prop will also provide more drag which will in turn labour the engine and quite probably lower your speed.

Cheers

[Roughasguts]

Nah what you wan't is to get the little motor to rev, I bet it's lugging.
So try raising the motor an inch at a time and check the improvement in speed if theres none well yeah change the prop.

[BaitThrower]

Do you mean actually lift the whole engine up on the transom? or just tilt the motor up on its position mount?

I tried various tilt positions but only small difference between any of them.

Most of the leg did seem buried underwater

[Roughasguts]

Yep raise the motor on the transom, un do the bolts and lift it up then tighten

You may need to make a backing plate or something, but the idea is the less the motor is in the water the more revs she can produce, to a certain point. Also there will be less leverage on the leg therefore not raising the nose and digging in the bum further causing more drag, eg slower.

[BaitThrower]

Yep raise the motor on the transom, un do the bolts and lift it up then tighten

You may need to make a backing plate or something, but the idea is the less the motor is in the water the more revs she can produce, to a certain point. Also there will be less leverage on the leg therefore not raising the nose and digging in the bum further causing more drag, eg slower.

Yeah digging in the bum seemed to be a major problem! I looked again at the transom and doesnt seem to be much room to go upward. Prolly only an inch. I think I will need more. Anyone got any pics of a backing plate thery have made so I have an idea what I need to make?

[BaitThrower]

Actually, I'm wondering if the motor I have is too long (i.e. a long shaft) for my short transom :(

With the motor fitted to the transom, shouldn't the cavitation plate be roughly level with the biottom of the transom? or no more than 1-2" lower (ideally)??
I read that somewhere :P

My transom height is 15 inches and length from bottom of mounting bracket to cavitation plate on the outboard is 18 inches... so I prolly need to raise her up about 2 inches or more above transom?

[finga]

Actually, I'm wondering if the motor I have is too long (i.e. a long shaft) for my short transom :(

With the motor fitted to the transom, shouldn't the cavitation plate be roughly level with the biottom of the transom? or no more than 1-2" lower (ideally)??
I read that somewhere :P

My transom height is 15 inches and length from bottom of mounting bracket to cavitation plate on the outboard is 18 inches... so I prolly need to raise her up about 2 inches or more above transom?
Yes that's correct. probably closer to 4 inches but keep in mind the poor little bugger is a 5Hp motor.
Getting 2 adults on the plane is a big ask to start with.

It seems silly but if you reduce the throttle and just motor along in displacement mode you might go faster then trying to get on the plane.

[BaitThrower]

Yeah I dont expect her to gun along with such a small motor, but just looking to get it set up as best as possible so she performs as well as she can for now :-)

I noticed full throttle was not worth it given only the small increase in speed achieved. I left it at 3/4 throttle most of the trip. I do think the motor is way too low though. I'll try lifting her up a few inches and see what happens.

[BaitThrower]

Well, looks like only room on the transom to lift her about half an inch :(
How can I lift it up further. I see jack plates etc but is my little transom sturdy enough to bolt one of those off it? Somehow I have doubts.

Also, there is this thing.... http://www.marineengine.com/products/accessory.php?in=1940400

Sounds like it might be viable?

[finga]

Mate for a 4hp an aluminium plate, say 6mm, would be heaps.
Seeing that you were in the Logan then you must be close to me.
If you can't find a bit of plate suitable give me a cooee.
I'll probably have something in the dungeon.

[BaitThrower]

Cheers mate. She's a 5HP but prolly not much weight difference anyway :)
I guess the thing is that whatever I add I will have to bolt to the transom anyway because to lift her up the 2 inches I need will mean the motor mount thumb screws will be higher than the top of the transom, so I can't just use the screw pressure to hold the ally plate against the transom under screw force alone (if that makes sense) Its a bit of an odd situation at the best ::)

[BaitThrower]

A an update, I built up the transom by bolting a nice chunky block of iron wood (it's a hardwood that is hard as iron) ontot he top of the transom (withy ply supporting pieces etc. All very rigid. This has raised the motor up a full three inches. I thought it was going to be quite high but my little boat sits pretty low in the water and at rest the cav plate is still about 2 inches below waterline. Under power the cav plate does not breach the churning surface water, so I guess that is ok? Performance does seem a lot better now.

I'm having a new 3-blade prop shipped in from the states (cheap as chips!) to replace the two-blade prop who's leading edges are really quite rough and gouged a little along their length. I'm sure the new, smooth 3-blade prop can only make things better.

I also think I need to distribute more weight up front. The stern really digs in under power. Too much weight down the back I think ::)

[Kleyny]

if you take and post a few piccies of how you have remounted the motor I'm sure you can find out if your on the right track.
IMO with the correct set up its not impossible to get it up on the plain with two adults.
you may also need to play with where you are sitting when trying to get it up

neil

[BaitThrower]

I have attached some piccies as requested.
Though they dont show the motor attached...

But the waterline when she is on water comes up to roughly the bottom of the rego number stickers. The cav plate on motor is in line with the bottom edge of the transom.

I think she just has too much weight up the back. But its an old boat hull and probably not designed to plane terribly well in the first place ::)

Anyway any tips or advice welcome.

[Kleyny]

try and get more weight up front when trying to get her up. the easiest way to do this is the driver leans and gets as far forward as you can get.

have you tried getting up on the plane with one person?

neil

[BaitThrower]

try and get more weight up front when trying to get her up. the easiest way to do this is the driver leans and gets as far forward as you can get.

have you tried getting up on the plane with one person?

neil

Yep more weight forward needed :) I'll try get my weight as forward as possible... but might need one of those tiller extension handles so i can move to the middle seat instead of the rear one.

[tin can marlin]

Hi mate i dont how to get the boat going better but she is a clean little boat.

[BaitThrower]

Hi mate i dont how to get the boat going better but she is a clean little boat.

Thanks :) Just needs a patchup paint job on some of the interior... looks like some parts were not properly prepared for paint so it didnt stick too well!
Otherwise not a bad entry level boat for a newbie :)