OMC FICHT RAM series

Most Trailer Boat readers would be familiar with combustion-related reliability problems experienced in the early FICHT 150/175 hp V-six. The subject of a number of news stories in these pages, the faults have been well publicised by OMC and its opposition alike.

Unfortunately, combustion chamber carboning at low revs is a fact of life with direct-injection engines whether they be two-stroke petrol or four-stroke diesel. (This is why most small automotive and marine diesels have indirect or swirl pre-combustion chambers). However, there are ways around this problem and with the launch of the new RAM series FICHTs OMC appears to have found the correct recipe.

The recently introduced FICHT RAM Injection system enhancements were reported in the January issue of Trailer Boat. As Dave Granville reported, the changes should result in significant improvement in powerhead longevity, low-speed emission levels and performance across the rev range particularly in the 150/175 hp models (those affected by the early problems).

Space precluded us from fully detailing the changes, particularly the arrival of OMC's own FICHT-friendly oil... So here goes...

Starting at the top, in addition to bold new cowls and graphics, the new RAM powerplants incorporate a cooling system with a water passage over the cylinder exhaust ports to reduce temperatures in this region. The system also directs the same amount of water to each cylinder bank to prevent hotspots between the banks.

A cylinder sleeve oiling system has been added. There are new oil hoses to the intake manifold, a higher pressure oil pump and oil recirculation. A hole in each piston skirt below the lower ring directs oil to the cylinder wall for reduced friction and less ring and bore wear. The pressurised oil is also injected at the crankshaft and wrist pin bearings for less friction under load.

The combustion chamber has been modified to include a deflector to direct fuel spray away from the spark plug. For the first time in FICHT history OMC has subcontracted out development to French fuel-injection specialist Sagem Inc, which has developed a 'toe seat' injector for better sealing during the injector stroke and more consistent spray patterns.

New 'Teaser' sparkplugs have also been fitted. These have a stepped centre electrode with a very narrow platinum tip to extend plug life and prevent late combustion due to plug-borne carbon deposits.

On the engine management side, in conjunction with Sagem, OMC has reprogrammed the Electronic Control Unit to lower the revs where the engine switches from stratified to homogenous combustion.

(At low revs the stratified or 'layered' levels of air/fuel mix are about 40:1, but as the torque band comes in homogenous mixing takes over and the air/fuel ratio increases to about 25:1. The use of stratified combustion enables the FICHTs to use significantly less fuel at trolling speeds than even the four-stroke competition. For example, according to OMC the FICHT 90 is 15% more fuel-efficient than the Honda BF90, while the FICHT 115 is a whopping 27% more efficient than the BF115).

With early FICHTs the switch to homogenous occurred at about 2800rpm and created a 'flat' spot here. Indeed, I remember back in 1997 an early FICHT 150 owner telling me that the mixing switch occurred right at the best wakeboarding speed.

Since then, OMC has lowered the mixing switch on all engines to eliminate the flat spot and reduce carboning-up at the start of the torque band. The programming is said now to be stair-stepped, that is the changeover is graduated.

A new part of the ECU circuitry (which already covers crankshaft and throttle position, air and water temperature and oil pressure to maintain the engine in peak operating condition) is the back pressure circuit. This functions above 1500rpm and commands the ECU to supply less fuel when there's more exhaust back pressure and more when there's less, reducing emissions and ensuring correct air/fuel ratios under all load conditions.

Most recently, OMC has introduced the new Evinrude FICHT RAM Injection Oil.

Specified for use with all FICHT models, the lubricant uses a 'polarised molecular' component known as 'CARB X'. According to OMC, this heavy duty solvent 'seeks out' carbon and holds it in suspension where it is expelled with exhaust gases. The oil itself is synthetic to increase biodegradability over mineral-based TC-W3 oils, while the 'CARB X' component is claimed to be 2.6 times more effective in reducing carbon than the normal TC-W3 solvent additives package.

The term 'CARB X' refers to the California Air Resources Board, which has decreed that outboards marketed in the US state must meet certain exhaust emission levels in the next few years through to 2007.

Another tough new US-based regulation is the Tahoe Regional Planning Agency (TRPA), which will limit outboards to four-strokes and direct- injection two-strokes on Lake Tahoe by 2001. Carburetted two-strokes will not be allowed to operate on this large alpine lake which borders California and Nevada.