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Old 25 June 2007, 15:19   #21
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Quote:
Originally Posted by Tims Osprey View Post
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
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Old 25 June 2007, 15:57   #22
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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.
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Old 25 June 2007, 16:09   #23
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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...
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Old 25 June 2007, 16:45   #24
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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.
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Old 25 June 2007, 17:15   #25
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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...
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Old 25 June 2007, 17:33   #26
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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 ?
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Old 25 June 2007, 17:38   #27
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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
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Old 25 June 2007, 17:43   #28
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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.
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Old 25 June 2007, 18:04   #29
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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
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Old 25 June 2007, 18:19   #30
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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>
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