MadMat

Does anyone know what the distance between drive centers on a 1989 292 sr1 should be?
I'm ordering hydraulic steering, but just want to double check my measurements b4 getting the cheque book out.
Thanks
Matt

RedDog382

Off the top of my head (at 5:30 A.M.) I think the center on my '89 311 was 34 and some fraction inches. Measure the tip to tip at the front of your drives and then propshaft centerline to centerline at the rear. They should be the same or very close, depending on toe in or out. You can also double check by measuring grease zerk to grease zerk on the upper part of the outer transom plate above the Merc decal. Also measure center to center of the cap on the drive where the zinc is bolted to the bottom of the cavitation plate on the upper housing on the drive. I think these numbers should all be the same.

MadMat

Thanks reddog! I measured 34 3/4, but the silent thunder box gets in the way a bit and the light was failing so I want to check my measurements.

Matt

RedDog382

You might want to check for a previous thread on hydraulic steering on Formulas. I know there can be a clearance problem with the silent thunder and the rams. I don't know of a good solution to this problem.

Formula Outlaw

On my 89' 311 it is exactly 34 and 1/2 inches measured from the front of the drives. The propshaft, center to center is 34 and 1/4 inches so I have a slight "toe-in". I am going to make them equal as with props turning "outward" when under "load" the props will tend to provide a "toe- in" via the resistance of the water so presently when at speed my drives "toe-in" is actually more than 1/4 of an inch.

MadMat

I'm going with Rams mounted between the drives, and using IMCO end caps, which If I mount the tie bar on the lower bracket and the rams on the upper will give me the maximum clearance, more than if I use wing plates anyway. I will also consider mounting an extra microswitch to limit travel if necessary, or even ditch the silent thunder platform if I have to. I consider good steering a must, but the silent thunder/swim platform combo is just a nice to have and can be sacrificed.

Formula Outlaw

I just finished a 379 (per Cuda Count) project on my boat which included ditching the Silent Thunder Box and going with Stainless Marine tips with the internal flappers.
I like the looks of the "classic" offshore boat and have always HATED those rectangular exhaust tips.

Between dropping the box and swapping to an Eddie Marine Thunder aluminum exhaust system, I lost over 400 lbs of dead weight right over the props. Docked, the boat now sits over an inch higher out of the water at the stern, so I just dropped an inch on my "X" demension. At least "it" thinks so. The first time I fired it off on the hose it was all worth it.-

MadMat

Yeh, I was watching your progress with interest. Unfortunately I boat exclusively in salt water, I'm pretty nervous about aluminium exhausts, plus on a pair of 330hp 7.4's I doubt a performance exhaust would make much difference unless I start changing the heads too, which the budget won't stretch too this year. I do know where there's a pair of bulldogs for sale though

MadMat

Do you mind me asking which tips you went for? Are they the 4" straight flange straight end with the internal 'super flap'? They look sweet.

Slick02

Had an 89 272sr1(same beam) and the measurements(I was trying to find headers that would fit) was 34.5" center to center on the nose.