Changing engine height

[Morlers]

I've been advised that raising my outboard by one hole should eliminate an anoying harmonic vibration I get transmitted throughout the boat (not bad just anoying and something I feel should not be there in a new boat and motor) from 2,700rpm-3,300rpm. The boat planes at around 3,500. The boat is a Haines Hunter 510 Breeze and the motor is a Johnson (read white Suzuki) 90hp 4 stroke. Currently, the anti-ventilation or cavitation plate is level with the keel so by raising the motor it will raise this by say 20mm.

Are there any pitfalls in doing this and can someone who has done it advise on method used ???

Thanks
:) :)

Morlers

[boatboy50]

Hey Morlers,
It may get rid of the problem, but could also introduce some ventilation or cavitation to the boat.
It should give you a better top end speed and allow the boat to rev out harder, but may cause more prop slippage.
Id try it and see how it goes, you can always go back.
It wouldnt be too hard to do at home, just need a block and tackle or an engine hoist, and enough time to do it and try it in one day. The engine has many holes so you wont need to redrill the transom, just change which hole the bolts go through.
Any mechanic could also do it for minimal cost.
Just make sure the holes get re-sealed again once its finalised, otherwise you could let water in to rot the transom.
Regards
Darren

[peterbo3]

Graeme,
Is this a new development? As you know, I have the same motor. I don't get that vibration nor should you. Check that your engine mount bolts are tight. If so, back to the dealer ASAP. Don't let em BS you about it being normal. Your motor is set at the correct height so there must be another issue.

[Morlers]

Hi Peter & Darren

Have been through dealer and direct to BRP Australia (who took dealers side totally). Both said it's the way I drive the boat. I should just punch it straight up on the plane and keep it there. I doo, but there are times when, because of chop/conditions, that I feel I should slow and when it drops off the plane I am into the vibrations. BRP says it's just harmonics developed by the engine at these revs as it is working har to get boat onto the plane...just something I have to live with.

I saw Steve from Solas Propellers at the Sanctuary Cove Boat Show and he says raising the motor will change the harmonics and fix the problem. I have a Solas HiRake 13 7/8 x 19 SS prop which Steve says was developed specifically for the Suzuki motor and that it can run higher in the water without ventiliation. He also says he has seen/heard of my problem before and that raising the motor eliminates the vibrations. I approached local dealer who outright said it won't fix the problem, just live with it. To be fair the dealer has been great in fixing all other problems I have had.

So I am prepared to raise the motor myself to give it a go. As Darren said I can always go back.

I don't have an engine hoist but had alernative thought. How about winding down the jockey wheel, lowering the tilt till skeg rests on a flat block of wood, undoing the nuts securing the motor mounting bracket, raising the jockey wheel a little till reaching the next hole and then tightening the nuts. Of course this will require at least two people, one to do the wpork and one to hold the motor upright.

Questions:
-Is it ok to support the motor on the skeg whilst doing this?
-Perhaps roping the motor through the engine support brackets to a roof joist to help support/keep upright?
-What sealant to seel holes...a netural cure silicone?
-Can I reuse the nylock nuts currently on or should I get new ones?

:) :)

Morlers

[Spaniard_King]

You don't need an engine hoist, I could do it at your house in 15 min. the largest thing I would be picking up would be a spanner to undo ya engine bolts.

tricks of the trade I suppose 8)

Garry

[Spaniard_King]

Morlers,

you are on the money,

firstly the lower engine bolts only need to be loosened. remove the top bolts, adjust the engine height using the jockey wheel (put a block of wood under the skeg...it will hold the weight fine) knock the top bolts through at the new #engine height. Use marine grade sika to seal the bolts.

Oh yeah, the nylocs will handle a couple of re tightens. I do make a point of checking engine security whenever I service an engine so hopefully your mechanic does too.

should only take 15 mins or so 8)

Garry

[Morlers]

Thanks for that Garry

I will have to undo the bottom nuts though as they are already at the bottom of the 'running holes'. There is one hole left under it though.

:) :)

Morlers

[NQCairns]

Hi Morlers, every engine does it, at least it can be measured if not felt. Your motor just might be one that does it a bit more than the one before and after on the production line or it could simply be tuning (dont just believe the factory got it right).
Try running some injector cleaner through it, and/or try a grade of fuel higher and see if it continues.

Failing that take it to another dealer and ask for a full re-tune (set timing again etc) and EFI recalibrate for the want of a beter word, I guess they are not carby those engines?

Like what has already been said in posts above you are being dazzled by bullshit there is nothing wrong with how you drive it who would buy an engine that only goes from 0 to 20knots at flatout and who would sell it!!

I don't know the Suzuki's so if it has a slide for the lower bolt holes a jack and spanner is all you need. Don't consider doing it by loosening the lowers all the way up then removing the upper bolts tilting the engine back on the loose lowers then sliding the upper bolts through the next lower engine hole (now angled to intersect the transom holes) and lever the whole job up -phew. It can or will do at lest some damage to the glass around the transom holes.

It always amazes me when someone states a prop is made or suits a particular engine ( like we jockey the engine without he boat for a day on the water ::)) The hull the engine bolts to is more than half of the equation.

What they are actually telling you is that you need raise your WOT RPM to make it easier for the engine to drive the boat at all RPM's, a good idea overall.
Raising the engine as far as they say may introduce more air and will allow less drag so the engine will be doing it easier but most probably less efficiently - RPM/distance traveled, too much slip.

Most people just run with what they are given and may change a prop but never raise their engine and then play with props so asking for advice from people with the same hull is mostly a waste of time unless they have tried to set it up properly. Your boat/engine may work great 20mm higher than the hull bottom, gotta suck it to see i guess.

The rule of thumb is 1 inch higher for every foot the engine sits behind the hull (the more moderate the deadrise the less true this rule becomes) so if you measure your current setback at the cav plate it will give you some idea of how high to start raising.

If it were my boat I would be looking at my WOT rpm then look toward raising a few hundred (unless way above manufacturers recommended already) with some prop choices, I would also start raising the engine but wouldn't expect it to work miracles, it might but there will be a trade of in efficiency compared to the right prop and the right height on transom for your hull/ style of driving, you will find this only by trial and error.
Good luck with it.nq

PS dont let just one person try and hold the engine upright it will end up on the ground, they just dont balance well on those skegs.

PPS don't discount a poor prop many new props are out of balance straight from the shelf with a degree of pitch or more difference between blades when flow tested, something like this can gang up and make a minor problem that much worse.

[Morlers]

Morning NQ

Thanks for the info. To put you more in the picture, the boat/motor has had this vibration from new and I have had four different props to get the revs right (ranged to 6,200rpm and hit rev limiter down to current prop at 5,600rpm). Max revs for engine via book is 5,500rpm so 5,600 sounds ok for the 13 7/8 x 19 SS prop.

I have annoyed hell out of dealer and BRP Aust to fix it but told its ok just live with it. I have phoned Suzuki Aust and they stated their engines don't vibrate and have had no other reported problem along this line. I have even spoken to other Haines Hunter/Johnson and Haines Signature/Suzuki dealers and they too say no reported problems.

I am willing to give raising the engine a go just to 'suck it and see'. I will get revs at various speeds before and after to compare performance.

Thanks for your time and input. I certainly appreciated it and will post results.

PS The Jophnson/suizuki is an EFI motor.

:) :)

Morlers