Quote:
Originally Posted by beamishken
To be honest Ive seen many ex vehicle engines converted & the results are rarely good even up to the 6.5l gm v8 they rarely end well. Usually ends up with a frustrated owner who's spent a fortune & spends more time arse up in an engine bay full of oil & coolant. Only ones that seem to hit reliability are the plodders in displacement boats where the required power output is way below the vehicle's power.
Yours seems to be a fueling issue, if it was turbo lag youd have black reek while spooling up, when manufacturers modify engines for marine (6lp yamaha etc) they alter the fuel system to suit the application. Injectors & pump are completely different set up without specialist equipment & access to a dyno the chances of getting it running 100%right are prety slim, will always be a compromise.
Whilst the 1.7 merc isnt a great engine, it does go well & is reasonably cheap to replace or overhaul & is specifically set up for marine use, if you still have it & the marinising gear replacing it may be your best option.
Sorry to pour cold water on your plans but seen many folk go down this route & spend a lot of time & money for mediocre results
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That's exactly what the 1.7 Merc is. It's a small car engine that accountants decided could be used in a boat. Yes it's cheap to run, most parts are interchangeable between the automotive engines. Yes I still have it but I don't plan on re fitting it. Here's a quick summary of all the problems I've encountered with that engine.
Turbo is prone to failure, not the same as the car engine expensive to replace. £1500 from mercruiser, £900 from turbo supplier if they can find one, it is not a common turbo.
Alloy head on cast iron block. It won't stand much over heating before head gasket let's go.
Intercooler and heat exchanger are poorly designed - lots of aluminium which corrodes in no time. Ridiculously expensive to replace.
The starter motor and alternator are in the bilge making them awkward to replace. Especially the starter... And you will be replacing them like pairs of socks!
There is the well known holes in pistons scenario but this can be avoided if turbo wastegate is kept working. Bin the stupid exhaust blanket and weld a stainless nut to the end of the wastegate arm so you can put a screwdriver through it and move it back and fore every so often. We blew pistons before knowing about this.
The little M8 exhaust manifold bolts will be seized in the head when you go to take the heat exchanger off. You have to drill them out tap them to 3/8unc and go stainless like it should been to start with.
If the timing belt let's go which it probably will the head will be scrap along with the cams (the lobes are pressed on and the knock will move them). If you're unlucky like me you'll crack a piston too.
Mercruiser in their wisdom have made sure absolutely no stainless steel fasteners have been used in the building of this engine. Hose clips will rust away and cap head screws and bolts will give you endless enjoyment trying to undo them when they're tiny little lumps of rust.
The engine is generally a horrible little turd of a thing to work on while it's in the boat. Everything is crammed together and you often end up taking a lot of stuff off just to get to the part you want to work on.
The ford 2.5 while maybe not the best engine out there for power to weight ratio or smoothness and quietness. certainly has a few advantages over the Isuzu 1.7
It's a slower turning, more industrial type engine. It would have been designed to operate for longer periods under full load. 2.5l 140hp at 3850rpm vs 1.7l 120hp at 4800rpm
Cast iron cylinder head and block should take a lot of abuse before letting go .
The starter and alternator are on the top, above deck level so unlikely to suffer from water damage even with the bilge flooded.
It's very easy to work on old fashioned push rod type of engine. Heat exchanger, intercooler, turbo, cylinder head, starter, alternator are all easy to remove and fit with the engine is still in the boat.
It has a proper water cooled marine turbo that should last much longer than that of the 1.7's dry turbo.
Push rod engine, if the timing belt goes it will only bend a few pushrods. Whip the rocker shaft out, new rods, time it up, throw belt on, bolt rocker down. Going again in 30mins. Could even do it at sea if you carry a spare belt and set of pushrods. The 1.7 would be game over.
Heat exchanger and intercooler are simple Bowman units salt water is never in contact with any aluminium parts. If needed, new tube stacks can be bought from Bowman for a fraction of the cost of the mercruiser equivalents.
Whoever marinised this engine has been very particular about it. All stainless steel fasteners and hose clamps, stainless manifold bolts, stainless cap head screws for the rocker cover etc. A much better job than mercruiser with their 1.7!
I already have the same performance as the 1.7, it also suffered pretty bad turbo lag but I'm just trying to get it 100% bang on. I reckon if I can get the lag issue sorted I can prop for a higher top speed. I should have an extra 20hp although she'll be about 100kg heavier.
