Zodiac Splitting transom at engine bolts - advise needed please

[mhb100]

Originally Posted by Tims Osprey

excessive prop ventilation and loss of power usually means that the engine has been installed to high on the transom which i thought was the case, can't be 100% sure though without seeing it and taking some measurements, so get somebody else to look at it and see what they think? if i lived any closer i would come along myself to check it out, what is the measurement from the top of the transom to the hull from the middle?

Tim, its 21" from top to bottom of transom

[Hightower]

I see from your first photographs that the hole in the bracket above the bolt position must have been used at some time, it might be worth lowering the outboard to this height. This might help your cornering, but will affect top speed a little.

[Nos4r2]

I spent quite a while looking at MHB100's boat yesterday and the engine height is about correct. It has what appears to be a very long pitch prop on with no numbers on it though which might account for the cavitation (and low top speed). It might also explain why the engine's been mounted higher-maybe as a 'best-worst option' by the dealer to raise the top speed to acceptable levels without messing around re-propping.

Anyway, back to the cracks...

[Tims Osprey]

Oh yer good point the cracks my guess is transom not coping to well with heavy Honda lump+ engine and or engine mount bolts being poorly situated+ possibly yoyo's theory about transom plate not being correct thickness thus causing uneven stress to transom = stress cracks in top of transom.

Remedy= check transom for any stress fractures or weak points, make good any damage to transom, have a stainless steel transom plate made up (one that goes both sides of the transom) check the height of the engine on the transom and possibly change the prop and you should then get 35-38 knots on wot.

[Endeavour]

I think when the inner liner has been bonded to the hull, their may have been a small cavity in the area where the engine is bolted. As the bolts have been tightened it has crushed a little and opened the joint which is now showing as a crack...

[Biggles]

So is this a major/proffesional repair or just a case of slapping in some home made gel coat to fill the crack, keep out the water and stop it happening again.

I'd be looking at throwing in some home made gel coat on a prepared surface and then fitting a stainless steel plate and making sure the engine is fitted with four bolts.

Is that the way MBH100 should do it ?

[mhb100]

QUOTE=Tims Osprey;206875] Trim the engine right down and measure the height of the cavitation plate to the bottom of the hull, is it level, just above or just under the hull? [/QUOTE]

Tim,

Visually it always looks ln line but I have just been and measured it,

as per the photo (above) the engine does not drop right back vertical with the transom but only as far as the photo which i guess is ok and normal? it has never gone lower before and always trims when in use so I'm assuming thats ok?


I've put a sprit level actually level with flat part underneath the stern hull and stuck it out towards the anti cavi plate and its about 2" lower or put it another way the engines about 2" higher - so yes could come down an inch?

So looks like I have 3 problems -

1) how do I lower it? - I have used engine hoists on old MG cars before but i dont think I have an eye on the honda block? whats the best way to use straps?. I'll also need to get some more bolts as the lower ones need grinding off as they have locks on the inside that i dont have keys to! and ill need some sealer - i guess this is easy to get - anyone recommend anywhere?

2) Honda say my model is 174kg, Zodiac say max load should be 165kg!!!! - but i've seen loads of 90's on zodiac - seems were all pushing our luck?

3) Prop - is 20 inch laser and I seem to get 5000 rpm WOT, manual says 90bhp at 5500. How can i find out what the prop should be for this model

or do you think the height of the engine could affect this performance?
or do you think the larger prop was an attempt to keep performance down?

any comments.....

Mark

PS i'm gonna contact a few dealers that sell Zodiac and Honda's for comments

[Tims Osprey]

No the engine should tilt down further than what is shown in the photo. don't go lowering the engine un till you have checked out that trim it looks to me like it should go much lower, that will be part if not all of the performance problem, i wish that i could come and have a look because its difficult to tell 100% from just pics.

[mhb100]

Tim

how can I lower it more ?
thats as far as it will go down electrically. I dont have a manual for it but logically could I raise it, put it on the transit brackets, then undo the fluid filler and then manually carefull lift it of the bracket and lower it down?

Mark

[Tims Osprey]

Mark the outboard should tilt down lower enough to engage the tilt stop bar or tilt tube on the mounting bracket, do you know what i mean? looks like you've got a problem with the tilt dude>

[Nos4r2]

Originally Posted by mhb100

I've put a sprit level actually level with flat part underneath the stern hull and stuck it out towards the anti cavi plate and its about 2" lower or put it another way the engines about 2" higher - so yes could come down an inch?

So looks like I have 3 problems -

1) how do I lower it? - I have used engine hoists on old MG cars before but i dont think I have an eye on the honda block? whats the best way to use straps?. I'll also need to get some more bolts as the lower ones need grinding off as they have locks on the inside that i dont have keys to! and ill need some sealer - i guess this is easy to get - anyone recommend anywhere?

Yep-Redline Outboards in Abingdon. You don't need to do more than support the weight to lower the engine on the bolts.Support then unbolt the engine,wind the jockey wheel down til the bolt holes are aligned as you want then bolt it back up.

Originally Posted by mhb100

2) Honda say my model is 174kg, Zodiac say max load should be 165kg!!!! - but i've seen loads of 90's on zodiac - seems were all pushing our luck?

I wouldn't stick the extra weight of a 5hp aux on there too then.

Originally Posted by mhb100

3) Prop - is 20 inch laser and I seem to get 5000 rpm WOT, manual says 90bhp at 5500. How can i find out what the prop should be for this model

It's not propped as per model but individually for the boat and engine combination with your usual load. I'd try a 17" first.

Originally Posted by mhb100

or do you think the height of the engine could affect this performance?

Yes. Lowering it will slow you down unless you're propped correctly.

Originally Posted by mhb100

or do you think the larger prop was an attempt to keep performance down?

No. I suspect that prop was what was on the engine when they sold you it and they tried to set the engine/boat up around the prop. It's the wrong way round to do it.


Would it help if I popped over again Mark? If you need a hand moving the engine on the bolts it'll be a lot easier with 2 people.

[mhb100]

Hi Tim,

Yes thanks for the info, I understand but it does not go that low!, its still resting on the rods from what i can see so they must be stopping it as i cant think of any other logical explanation?

Mark

[Nos4r2]

Originally Posted by mhb100

Hi Tim,

Yes thanks for the info, I understand but it does not go that low!, its still resting on the rods from what i can see so they must be stopping it as i cant think of any other logical explanation?

Mark

The rods are your trim cylinders-they should move too.

[Tims Osprey]

It seems that you have more than one problem there dude, the trim is not swinging lower enough and the prop is a miss match, i will come and have a look if you want, have you got a Honda manual that covers the tilt system?

[mhb100]

If you have time to pop around again thats cool. I commute so I'm not around until 7pm weekdays, but have sometime on weekends...

I think my plan is :-

1) to sort out the trim/tilt first to see what's going on their - another problem!
2) then ill be able to get a true check of the cavi plate and transom height
3) Repair cracks around the motor (as best i can - hence i might need a hoist)
4) drop the motor one bolt hole - if needed

take it for a spin somewhere sensible

5) swap the prop......

[mhb100]

Originally Posted by Nos4r2

The rods are your trim cylinders-they should move too.

Hi Nos,

yep, but they dont appear to be moving enough - ill have another look tomorrow. I've never checked the fluids as i assumed they have during servicing so it probably a good idea to check ...

Mark

[Nos4r2]

Not a problem Mark.

It's good to know that you didn't find any exposed wood down the crack. That was the biggest worry I had when I looked in there.

I think you're on the right track with your action plan

[mhb100]

Originally Posted by Tims Osprey

It seems that you have more than one problem there dude, the trim is not swinging lower enough and the prop is a miss match, i will come and have a look if you want, have you got a Honda manual that covers the tilt system?

Hi Tim

I downloaded a handbook from honda's website but its not a technical one. I'll see what i can find on the web,etc

thanks for the offer to come over mate - but dont worry for the moment. I think Nos might pop over again sometime - and if we get stuck I'll bring it over to Bristol for your comments!!

I guess i need to start learning about all this stuff sooner than later....

Cheers
Mark

[Tims Osprey]

yer no worries, looks like your in good hands with nos anyway, good luck, cheers, Tim.

[Nos4r2]

Originally Posted by Tims Osprey

yer no worries, looks like your in good hands with nos anyway, good luck, cheers, Tim.

Just worry if he turns up to the Priory Bay Picnic twitching slightly and mumbling about Seariders