Sierra 18-5311 Contact Set for Mercruiser 110, 120, 140, 2.5L, 3.0L I/O Engines - Replaces Mercruiser 34235

The Sierra 18-5311 is a marine ignition contact set (breaker points) built for contact-controlled distributor ignition systems on Mercruiser stern drive engines, standard rotation, excluding Thunderbolt ignition. It is the correct contact set for the Mercruiser 110, 120, and 140 models, as well as the 2.5L and 3.0L L4 engines, matching the tune-up kit and distributor components used across these engine families. As the wear item that opens and closes the primary ignition circuit inside the distributor, the contact set directly affects spark timing and engine starting reliability, so it is a standard replacement during a tune-up or when points become pitted, worn, or out of adjustment.

Constructed with a glass-reinforced base and finished in white, the 18-5311 is built to meet or exceed original equipment quality so it drops into the distributor housing in place of the factory points without modification. It is sold as a single contact set (quantity of 1) and is intended to be paired with the matching rotor, distributor cap, coil, and spark plug wires for a complete tune-up on these applications.

Specifications

• Brand: Sierra
• Manufacturer Part Number: 18-5311
• Product Type: Ignition Contact Set
• Material: Glass
• Color: White
• Weight: 0.06 pounds
• UPC: 030999236609
• Unit Count: 1
• Ignition Type: Contact-controlled distributor, standard rotation, excludes Thunderbolt ignition
• Fitment: Mercruiser 110, 120, 140 (153/181 cid L4), 2.5L, and 3.0L L4 I/O engines
• OEM Cross-Reference: Chris-Craft 16.69-00049; GLM 70020; Mallory 9-29006; Mercruiser 34235, 34235T, 35637; OMC 380538

Fitment

• Mercruiser 110 (153 cid/L4), model years 1963-1966, serial numbers 1537370-2044033
• Mercruiser 120 (153 cid/L4), model years 1964-1986, serial numbers 1666601-B531853
• Mercruiser 2.5L (153 cid/L4), model years 1987-1989, serial numbers B531854-C853255
• Mercruiser 140 (181 cid/L4), model years 1968-1986, serial numbers 2508261-B450800
• Mercruiser 3.0L (181 cid/L4), model years 1987-1989, serial numbers B450801-C856558

Replaces (OEM)

• Chris-Craft 16.69-00049
• GLM 70020
• Mallory 9-29006
• Mercruiser 34235
• Mercruiser 34235T
• Mercruiser 35637
• OMC 380538

Frequently Asked Questions

What engines does the Sierra 18-5311 contact set fit? The 18-5311 fits Mercruiser 110 (1963-1966), 120 (1964-1986), 140 (1968-1986), 2.5L (1987-1989), and 3.0L (1987-1989) I/O engines, all 153 or 181 cid L4 models using a contact-controlled distributor with standard rotation (not Thunderbolt ignition).

Is 18-5311 the same as Mercruiser part 34235? Yes, Sierra 18-5311 is a direct equivalent to Mercruiser 34235 and 34235T, as well as Chris-Craft 16.69-00049, GLM 70020, Mallory 9-29006, Mercruiser 35637, and OMC 380538.

How much does the 18-5311 contact set weigh? The Sierra 18-5311 contact set weighs 0.06 pounds.

What is the contact set made of? The 18-5311 contact set uses a glass-reinforced base finished in white, matching the color and construction of the original equipment contact points.

Does this contact set work with Thunderbolt ignition systems? No, the 18-5311 is designed for contact-controlled distributor systems with standard rotation and specifically excludes Thunderbolt ignition applications.

What comes in the box with the 18-5311? Each order includes one Sierra 18-5311 contact set, sold as a single unit count of 1.

Do I need to replace other ignition parts along with the contact set? For a complete tune-up on Mercruiser 110, 120, 140, 2.5L, or 3.0L engines, the contact set is typically replaced along with the matching rotor, distributor cap, coil, and spark plug wires for that model.

Is Sierra 18-5311 an OEM or aftermarket part? The 18-5311 is an aftermarket replacement built to meet or exceed original equipment quality, cross-referencing directly to OEM numbers like Mercruiser 34235 and OMC 380538.

Will 18-5311 fit a Mercruiser 3.0L from 1990 or later? No, the 18-5311 contact set applies to the 3.0L 181/L4 engine for model years 1987-1989; later 3.0L serial ranges use a different contact set.

What color is the 18-5311 contact set? The Sierra 18-5311 contact set is white.

How do I know if my contact set needs replacing? Pitted, burned, or misadjusted contact points on the distributor commonly cause hard starting or rough idle, and replacing the 18-5311 contact set is the standard fix during a tune-up on these Mercruiser applications.