Merry Fisher 705 Performance

[crossy]

Hi All,

I have now had the engine checked over and other than an issue with the alternator cable there is nothing wrong with that.

I took it out for a spin and with me sitting on top of the anchor locker (to simulate 110' of chain) we were still limited to 14 knots at 3,700 rpm (has my wife driving and keeping an eye on rpm and gps).

Had the boat lifted out and the bum is clean as a whistle and prop looked OK.

Am now totally stumped.......? The only thing left is to send to prop off to propellor solutions for checking out.

Any suggestions welcome,
Andrew

 

[NoviceRod]

Hi All,


The only other thing is the weight of chain I removed from the nose but I the TABS sort out the trim for me so this shouldn't be an issue?

Andrew

Just noticed this, I do not have tabs on mine, didn't think they were fitted to 705. If you have them, that might be the problem!

 

[crossy]

Just noticed this, I do not have tabs on mine, didn't think they were fitted to 705. If you have them, that might be the problem!

Hi Rodney,

Yes, this is the only thing to have changed (other than the weight distribution) since I did manage to get a 16/17 knot fast cruise.

Worth taking them off to see I guess.

Andrew

 

[crossy]

Well, this is really starting to drive me up the wall.

I have monkeyed about with weight distribution and this seems to make no difference to the performance.

I have now bought a chip to boost the engine to 175hp (14 day money back guarantee so thought why not give it a go) and this didn't sort it out either.

at 150hp:
3,600 rpm speed 14 knots, 3,600 rpm engine load 100%, max rpm 3,680 (should be 4,000)

at 175hp:
3,600 rpm speed 14.5 knots, 3,600 rpm engine load 82%, max rpm 3,850 (should be 4,000)

The chip has meant that the engine is running under much less load which is good but the cruising speed is still 3 knots down, a friend with a 695 and the Nanni 175hp engine in had a cruising speed of 18 knots.

Just wondering whether anyone has any final suggestions before I strap solid fuel rocket booster to the transom in an attempt to find those extra few knots?

Cheers,
Andrew