Repowering question

ExcaliburII

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Still considering the possibilities with restoring this Sun Runner.

http://www.ybw.com/forums/showflat.php/Cat/0/Number/2273288/an/0/page/5#2273288

Can anyone advise what my options would be for replacing the existing AQ131/290SP drives without major rebuilding of the transom if the existing units are not useable? For example, would I be able to fit a Mercruiser on a Bravo drive in the same cutouts, or would I have to stick with Volvo's finest? If Mercruisers are not an option, will any other make fit? Not worried at this stage about room in the engine bay - that's a different issue - just compatibility with the transom cutouts.

I don't mind opening them out a bit and/or filling & redrilling the bolt holes but I don't really want to get into reworking the whole transom to fit units that need smaller cutouts.

Anyone help?
 

ExcaliburII

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Hmm, I was afraid that was going to be the answer.

I have a (possibly unfounded) slight uneasiness about Volvo stuff as there always seem to be a lot of grumbles on here about reliability, cost of spares etc. Conversely, I have always run Mercury outboards with very few problems over many years, and all relatively minor, and Excalibur II's Mercruiser has hardly put a foot wrong over the 9 years we have been together *adopts wistful gaze and touches wood* Perhaps I'm being paranoid and a posse of indignant Volvo fans will be along soon to tell me how wrong I am. /forums/images/graemlins/grin.gif /forums/images/graemlins/grin.gif

Does any other make of drive use the same size or larger hole than Volvo?

The coastal rides link doesn't work for me, btw.
 

alruss

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Volvo 290's are rated at 300hp, aq131 are nowhere near that so they will probably be OK. My volvo outdrives are only rated at 130hp and running with 120hp engines, they are 40 years old this year and still running. I would think the engines being rebuilt/ replaced is a greater worry. Rebuilt 290 drives can be purchased for £1000.00 and yours rebuilt for less if that helps with your decision. IVSS is the company, no connection, I have used for this work. PM me for tel no.if required.
 

ExcaliburII

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Thanks for the info, alruss.

I can see that having the existing drives reconditioned would be the cheapest option, but I would be concerned whether they could handle the extra torque if I changed the AQ131s for equivalent diesels. Having said that, I didn't realise they could take 300HP, so maybe not such a problem.

My main difficulty is having no idea what is the optimum (or even max designed) power for this boat. I don't know whether the old AQ131s were barely adequate when new or whether they would have made it fly. So I need to amass more knowledge before deciding what engines to go for and hence whether I need to change the drives for a different model or not. The whole prospect is still a very fluid mix of options and it will only start to gel and ultimately set as I find out more.

Tel no: for IVSS would be useful either way. Can you PM it to me if you don't want to publish it on the forum, please? TIA
 

JKay

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I run Aq131's in a Fairline Carrera and its just enough for 27 knots clean and light,after a year in fresh water I,m at 19 knots they are only rated at 120 hp when new.If you scource te parts from the motor factors such as GSF then they are cheap as a chippy /forums/images/graemlins/grin.gifeg fanbelts£2.50 cambelts£16.00
etc
 

spannerman

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I have repowered at least 20 Vplvo powered boats with Mercruiser, there is an adapter plate available which sits in the old Volvo hole and then you bolt the new Merc straight in, its virtually plug and play.
Obviously there may be reworking of the engine mounts depending what motor you choose, if its a petrol the mounts will be the same as VP use the same GM blocks as Mercruiser.
 

ExcaliburII

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Spannerman - Brilliant! Thanks for that, it's just the sort of thing I needed to hear as it helps me to keep my options open. I would much prefer to bolt in a properly designed adapter than faff about with the transom if I decide to go the Mercruiser route. Is the adaptor made by Mercruiser or an independant company?

Jkay - I was shown some paperwork by my bil (current owner of the vessel in question) that referred to the AQ131s as 230HP and I assumed that was each. If they are only 120 or so, as you suggest, I would obviously have to consider the need/ wisdom of putting in something like 250HP a side. /forums/images/graemlins/shocked.gif
 

spannerman

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Its made by Mercruiser part No 827691A 1, and will convert Volvo and BMW installations to Alpha and Bravo drives.
 

tico

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Alternatively you may want to fit the 145hp diesels from Mike at Lancing Maring.

Straightforward simple engines, that will mate and run well with the 290SP legs... you will need to change the props tho to optimise performance, but the legs will happily handle the extra torque. (Have fitted them to a Sunfury)
 

ExcaliburII

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Spannerman - many thanks! /forums/images/graemlins/smirk.gif

Tico - good suggestion, just had a quick look at LM's website, thanks. That may turn out to be the cheapest (& most sensible) option. My main fear is that I don't know yet whether the existing 290SP drives would be salvageable with any confidence as they look pretty ropey. So, if I will need to change them anyway, my decision tree starts with a transom with two volvo-shaped holes in it and all viable options on the table.

Thanks again to all for suggestions - keep 'em coming. /forums/images/graemlins/grin.gif /forums/images/graemlins/grin.gif
 

tico

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no necessarily
with AQ171s on 290 legs the props were 'short hub' 16x17.WOT revs 5000-5500

With 140hp diesels WOT revs 4000
needed 'Long hub' 16x21 props altered to 22" pitch and 1" of cupping by steel developments.

no change to gear ratio. Worked beautifully!

it's all to do with the torque and the way the props transmit power.
Basically, the smaller blade area of the short hubs allow the prop to 'slip' a little on acceleration allowing the revs to build and reach the max power band of the engine before the slip drops away as the boat accelerates.
With diesels, the larger blade area of the long hubs make best use of the torque, by allowing less slip on acceleration and the larger pitch compensates for the lower revs (albeit higher torque)
Thats it technically speakin!
 

AndieMac

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Excalibur.. Are you doing this reno to keep the boat, or to on sell?
If you want to keep her and you are repowering, it may well be worth a thought to bit the bullet and replace the whole caboose. (key to prop)
I doubt if there will be a better time to negotiate a favourable deal on a complete set-up as currently.
 

ExcaliburII

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Probably to keep for a bit, I'm certainly not expecting to make a handsome profit out of it. /forums/images/graemlins/grin.gif /forums/images/graemlins/grin.gif /forums/images/graemlins/grin.gif

She's only a few feet longer than my Bayliner, but much taller, so she feels a lot bigger and seems like a step up the ladder. It will probably take me at least 18 months to do all the work in any case. The likely scenario, if all turns out well, is that I would then sell the Bayliner and keep the Sun Runner, so I want to tackle the renovation on that basis. Hence, I'm looking at all the options for repowering before I start. I will certainly need to look for the keenest deal I can find but, at the moment I'm still trying to work out how much power the thing actually needs to make it perform well.
 
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